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Solid_state_hydrogen_storage

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!001

Efficient storage technology (absorption and desorption) is the key to boom the application of hydrogen as energy storage media. Among the solid-state hydrogen storage materials, magnesium-based material exhibits many advantages and is considered one of the most promising materials. However, the disadvantages including poor hydrogen absorption, desorption kinetics and high operating temperature still need to be modified. The addition of catalysts is one of the optimal ways to improve the kinetic performance of MgH2. However, transition metal-based catalysts exhibit excellent catalytic performance. This work mainly summarizes the addition of Co/Ni/Fe-based catalysts on the hydrogen storage performances of Mg. While examining the differences in the performance of each catalyst, some future research perspectives are also illustrated.

Among the solid-state hydrogen storage materials, magnesium-based material exhibits many advantages and is considered one of the most promising materials. However, the disadvantages including poor hydrogen absorption, desorption kinetics and high operating temperature still need to be modified.

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!002

Developing safer and more efficient hydrogen storage technology is a pivotal step to realizing the hydrogen economy. Owing to the lightweight, high hydrogen storage density and abundant reserves, MgH2 has been widely studied as one of the most promising solid-state hydrogen storage materials. However, defects such as stable thermodynamics, sluggish kinetics and rapid capacity decay have seriously hindered its practical application. This article reviews recent advances in catalyst doping and nanostructures for improved kinetic performance of MgH2/Mg systems for hydrogen release/absorption, the tuning of their thermodynamic stability properties by alloying and reactant destabilization, and the dual thermodynamic and kinetic optimization of the MgH2/Mg system achieved by nanoconfinement with in situ catalysis and ball milling with in situ aerosol spraying, aiming to open new perspectives for the scale-up of MgH2 for hydrogen storage applications.

Owing to the lightweight, high hydrogen storage density and abundant reserves, MgH2 has been widely studied as one of the most promising solid-state hydrogen storage materials. However, defects such as stable thermodynamics, sluggish kinetics and rapid capacity decay have seriously hindered its practical application.

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!003

MgH2, as one of the typical solid-state hydrogen storage materials, has attracted extensive attention. However, the slow kinetics and poor cycle stability limit its application. In this work, LiBH4 and YNi5 alloy were co-added as additives to MgH2 via ball milling, thereby realizing an excellent dehydrogenation performance and good cycle stability at 300 °C. The MgH2-0.04LiBH4-0.01YNi5 composite can release 7 wt.% of hydrogen in around 10 min at 300 °C and still have a reversible hydrogen storage capacity of 6.42 wt.% after 110 cycles, with a capacity retention rate as high as 90.3 % based on the second dehydrogenation capacity. The FTIR results show that LiBH4 can reversibly absorb and desorb hydrogen throughout the hydrogen ab/desorption process, which contributes a portion of the reversible hydrogen storage capacity to the MgH2-0.04LiBH4-0.01YNi5 composite. Due to the small amount of LiBH4 and YNi5, the dehydrogenation activation energy of MgH2 did not decrease significantly, nor did the dehydrogenation enthalpy (∆H) change. However, the MgNi3B2 and in-situ formed YH3 during the hydrogen absorption/desorption cycles is not only beneficial to the improvement of the kinetics performance for MgH2 but also improves its cycle stability. This work provides a straightforward method for developing high reversible hydrogen capacity on Mg-based hydrogen storage materials with moderate kinetic performance.

MgH2, as one of the typical solid-state hydrogen storage materials, has attracted extensive attention. However, the slow kinetics and poor cycle stability limit its application.

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!004

MgH2 has been attracted extensive attention because of its superior hydrogen storage performance and good reversibility. Further improvement of its kinetics and thermodynamic performances is needed to achieve widespread application. This article investigated the hydrogen storage properties of the thermodynamic optimized Mg-TiCrV hydrogen storage composite modified by layered Ti3C2 materials containing different 3d transition metal particles (Fe, Co, Ni). Mg-TiCrV/Ti3C2-X (X = Fe, Co, Ni) composites can absorb more than 5.30 wt% hydrogen within 1 min at 453 K under 3 MPa hydrogen pressure, and desorb more than 5.25 wt% hydrogen within 60 min at 543 K to 0.1 MPa. In particular, Mg-TiCrV/Ti3C2-Ni composite exhibited the best hydrogen storage properties, which can desorb 4.98 wt% hydrogen within 60 min at 523 K to 0.1 MPa hydrogen pressure and absorb 5.80 wt% hydrogen within 1 min at 453 K under 3 MPa hydrogen pressure. Structural analysis shows that the synergistic effect of layered material Ti3C2 and Ni particles promote the hydrogen release and uptake process.

MgH2 has been attracted extensive attention because of its superior hydrogen storage performance and good reversibility. Further improvement of its kinetics and thermodynamic performances is needed to achieve widespread application.

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!005

The design of catalysts with excellent catalytic activity plays an important role in the field of solid-state hydrogen storage of new energy sources. Herein, a novel hydrangea-like NiO@NiMoO4 composite catalyst was prepared through a facile hydrothermal reaction. Subsequently, NiO@NiMoO4 was doped into MgH2 by ball milling to solve the problems of high dehydrogenation temperature and slow desorption kinetics of MgH2. It can be seen from the experimental results that the MgH2 + 10 wt% NiO@NiMoO4 composite starts to dehydrogenate at about 190 °C, which is about 170 °C lower than that of pure MgH2. Meanwhile, after complete dehydrogenation, the composites can start to absorb hydrogen below 40 °C. Compared with pure MgH2, the activation energy of hydrogen absorption and dehydrogenation of the composite decreased by 47.6 kJ/mol and 46.5 kJ/mol, respectively. In 10th cycle tests, the MgH2 + 10 wt% NiO@NiMoO4 composite still has good cycle stability. After adding a small amount of biomass charcoal, the hydrogen storage capacity can even be maintained above 97%. Furthermore, the characterization results show that the in situ generated new species Mo and Mg2Ni/Mg2NiH4 synergistically promote the adsorption and dissociation of hydrogen. This new synergistic mechanism provides new comprehensive insights for improving reversible hydrogen storage in MgH2

Meanwhile, after complete dehydrogenation, the composites can start to absorb hydrogen below 40 °C. After adding a small amount of biomass charcoal, the hydrogen storage capacity can even be maintained above 97%.

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!006

The 0.55LiBH4-0.45Mg(BH4)2 (LMBH) eutectic composite is promising for solid-state hydrogen storage, as it exhibits a high hydrogen capacity and a very low initial dehydrogenation temperature. However, its main hydrogen release steps still require higher temperatures. In the present study, few-layer Ti2C has been synthesized and utilized as catalysts in the LMBH. Compositing LMBH with varying amounts of Ti2C (10, 20, 30, and 40 wt%) results in low initial dehydrogenation temperatures (164–110 °C), fast desorption rates and high hydrogen capacities (7.5–10.5 wt%) at a low temperature of 260 °C. The LMBH-30Ti2C composite yields 6.5 wt% H2 even at as low as 200 °C. Additionally, the LMBH-30Ti2C composite could reversibly store 3.5 wt% H2 during the second to fourth dehydrogenation cycles without degradation. The outstanding hydrogen storage performance could be attributed to decomposition driven by reactions between high-valence Ti ions and LMBH, the in-situ formation of the active metal Ti catalyst, and the prevention of aggregation in the Ti2C-doped LMBH. © 2023 Elsevier B.V.

However, its main hydrogen release steps still require higher temperatures. Compositing LMBH with varying amounts of Ti2C (10, 20, 30, and 40 wt%) results in low initial dehydrogenation temperatures (164–110 °C), fast desorption rates and high hydrogen capacities (7.5–10.5 wt%) at a low temperature of 260 °C.

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!007

Magnesium hydride is one of the most sought-after materials for solid state hydrogen storage due to its low cost and high gravimetric capacity (7.6 wt% hydrogen). However, high temperature of desorption (>350 °C) and slow kinetics limit its use for commercial on-board applications. In this work, accumulative roll bonding (ARB) technique has been utilized to synthesise Mg–LaNi5–Mg2Ni-soot hybrid with enhanced hydrogen storage properties. It is seen that the hybrid absorbs ∼6.2 wt% hydrogen at a plateau pressure of ∼2 bar at 300 °C and exhibits fast kinetics with ∼6.6 wt% hydrogen absorption within ∼30 min at 300 °C and 20 bar hydrogen pressure. The role of Mg2Ni as a catalyst as well as hydrogen absorbing medium provides an effect akin to ‘hydrogen pump’, thus enhancing the rate of hydrogen absorption. Presence of carbon in various forms such as aciniform, carbonaceous microgel and cenospheres (derived from soot) plays a vital role by providing channels for diffusion of hydrogen through the hybrid. The ARB technique provides an inexpensive and scalable method of synthesis of Mg based hybrids with large number of interfaces and high amount of strain leading to enhanced hydrogen storage properties. © 2023 Hydrogen Energy Publications LLC

However, high temperature of desorption (>350 °C) and slow kinetics limit its use for commercial on-board applications. In this work, accumulative roll bonding (ARB) technique has been utilized to synthesise Mg–LaNi5–Mg2Ni-soot hybrid with enhanced hydrogen storage properties.

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Herein, a novel approach by designing Schottky-structured CoNi nano-alloys were introduced. After compositing with MgH2, its initial hydrogen absorption started at a low temperature of 40 °C. At a temperature of 300 °C, 6.5 wt% of H2 was released in only 10 min. Furthermore, the kinetic analysis revealed a pivotal transformation in the control model for dehydrogenation of MgH2, shifted from surface penetration to diffusion at a moderate temperature of 250 °C with the introduction of CoNi-CoO@rGO. After modification, the activation energy for hydrogen de/absorption decreased from 116 kJ/mol and 79.39 kJ/mol, to 66 kJ/mol and 54.39 kJ/mol, respectively. It is noteworthy that the CoNi-CoO@rGO-modified MgH2 exhibited excellent cycling performance, retained an impressive hydrogen storage capacity of 97% after 20 cycles at 300 °C. The innovation of this work lies in the following three aspects: 1) the uniform distribution of CoNi-CoO@rGO nanoparticles on the surface of MgH2 significantly enhanced the contact area and promoted the catalytic activity, 2) the synergistic effect between Mg2Co-Mg2CoH5 and Mg2Ni-Mg2NiH4 attenuate the intensity of the Mg-H bond and quickened the post-discharge of MgH2, 3) the incorporation of a CoO-induced Schottky structure accelerated the H transfer in MgH2 and improved the hydrogen absorption and release efficiency. © 2023 Elsevier B.V.

After compositing with MgH2, its initial hydrogen absorption started at a low temperature of 40 °C. It is noteworthy that the CoNi-CoO@rGO-modified MgH2 exhibited excellent cycling performance, retained an impressive hydrogen storage capacity of 97% after 20 cycles at 300 °C.

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!009

Despite the promise of TiFe-based alloys as low-cost solid-state hydrogen storage materials with mild operating conditions and reasonable hydrogen capacity, their initial hydrogenation process is difficult, hindering broad utilization. The effect of alloying element on the initial hydrogenation kinetics of TiFe alloys, TiFe0.9M0.1 (M = V, Cr, Fe, Co and Ni), was evaluated by analyzing changes to the passivating surface oxide layer that inhibits hydrogen permeation, as well as the ease of initial-stage hydrogen absorption into the underlying matrix. X-ray photoelectron spectroscopy and atom probe tomography revealed key variations in surface oxide compositions and thinning of the passivating oxide layer compared to pure TiFe, which suggests suppressed oxide growth by alloying-induced elemental redistribution. At the same time, density functional theory calculations predicted exothermic formation of hydride nuclei when alloying with V or Cr, as well as a reduced nucleation barrier when alloying with Co or Ni. Overall, these results are consistent with the observed experimental trend of the activation kinetics. We propose that improvements in activation kinetics of TiFe with alloying arises from the combined effect of reduced passivating oxide thickness and easier hydride nucleation, offering a starting point for alloy design strategies towards further improvement. © 2022 The Author(s)

At the same time, density functional theory calculations predicted exothermic formation of hydride nuclei when alloying with V or Cr, as well as a reduced nucleation barrier when alloying with Co or Ni. We propose that improvements in activation kinetics of TiFe with alloying arises from the combined effect of reduced passivating oxide thickness and easier hydride nucleation, offering a starting point for alloy design strategies towards further improvement.

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!010

NaH and LiH are theoretically capable of storing hydrogen, but several challenges remain to be overcome before they can be widely used for hydrogen storage. In this study, LiH and NaH were ball-milled and the effect of surface area and hydrogen pressure on hydrogen storage capacity was investigated using the solid-state hydrogen storage method. XRD patterns and Raman spectra show significant shifts in main peak positions of LiH and NaH after hydrogen adsorption. BET analysis shows a significant increase in the specific surface area of LiH and NaH from 6.25 m2/g to 12.35 m2/g and from 1.34 m2/g to 2.33 m2/g respectively due to ball milling. The FTIR spectra showed more bonds in the 400–1200 cm⁻1 fingerprint region after storing hydrogen in LiH and NaH. This suggests structural changes with enhanced bond bending due to hydrogen. At 9 bar pressure, LiH and NaH exhibited excellent hydrogen storage, with ball-milled LiH reaching about 3.55 wt% and 652 sccm, and NaH achieving approximately 1.58 wt% and 291 sccm. These results highlight the significant influence of surface area and hydrogen pressure on hydrogen storage potential. Incorporating the storage potential within the evaluation of PEM fuel cell performance, we suggest that an increased storage capacity directly corresponds to an augmented power density. The analysis of power density over time revealed that the hydrogen adsorbed ball-milled LiH exhibited the highest power density, peaking at 0.075 Wcm−2 over the long term. In contrast, LiH displayed a lower power density (0.025 Wcm−2) while maintaining its long-term performance. The hydrogen adsorbed NaH and hydrogen adsorbed ball-milled NaH displayed power densities 0.050 Wcm−2 and 0.073 Wcm−2, respectively, but they showed short-term performance. © 2023 Elsevier Inc.

This suggests structural changes with enhanced bond bending due to hydrogen. In contrast, LiH displayed a lower power density (0.025 Wcm−2) while maintaining its long-term performance.

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The first principle of calculation is a computational technique based on quantum mechanics that may precisely determine the ground-state electronic structure and associated mechanical and thermodynamic characteristics of solid materials. This study explains the history of first-principles development, calculation techniques, and the use of ultra-soft pseudopotential in hydrogen storage materials based on an inquiry and analysis of the findings of previous research. This paper primarily reviews the research progress of first principles in improving two-dimensional hydrogen storage materials, metal-organic framework materials, alkali metal-base composite hydrides, and metal-base hydrogen storage materials in order to speculate on the hydrogen storage mechanisms of materials. It is possible to estimate the location of hydrogen adsorption in a material by computing its electronic structure, band structure, electron density, and lattice vibration. This information is then used to compute the hypothetical new hydrogen storage material. Finally, the direction of first-principles computing in hydrogen storage materials is anticipated. © 2023 Hydrogen Energy Publications LLC

The first principle of calculation is a computational technique based on quantum mechanics that may precisely determine the ground-state electronic structure and associated mechanical and thermodynamic characteristics of solid materials. This information is then used to compute the hypothetical new hydrogen storage material.

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Magnesium hydride is one of the most promising solid-state hydrogen storage materials for on-board application. Hydrogen desorption from MgH2 is accompanied by the formation of the Mg/MgH2 interfaces, which may play a key role in the further dehydrogenation process. In this work, first-principles calculations have been used to understand the dehydrogenation properties of the Mg(0001)/MgH2(110) interface. It is found that the Mg(0001)/MgH2(110) interface can weaken the Mg–H bond. The removal energies for hydrogen atoms in the interface zone are significantly lower compared to those of bulk MgH2. In terms of H mobility, hydrogen diffusion within the interface as well as into the Mg matrix is considered. The calculated energy barriers reveal that the migration of hydrogen atoms in the interface zone is easier than that in the bulk MgH2. Based on the hydrogen removal energies and diffusion barriers, we conclude that the formation of the Mg(0001)/MgH2(110) interface facilitates the dehydrogenation process of magnesium hydride. © 2024 The Authors

Magnesium hydride is one of the most promising solid-state hydrogen storage materials for on-board application. In terms of H mobility, hydrogen diffusion within the interface as well as into the Mg matrix is considered.

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!013

Hydrogen storage is a key link in hydrogen economy, where solid-state hydrogen storage is considered as the most promising approach because it can meet the requirement of high density and safety. Thereinto, magnesium-based materials (MgH2) are currently deemed as an attractive candidate due to the potentially high hydrogen storage density (7.6 wt%), however, the stable thermodynamics and slow kinetics limit the practical application. In this study, we design a ternary transition metal sulfide FeNi2S4 with a hollow balloon structure as a catalyst of MgH2 to address the above issues by constructing a MgH2/Mg2NiH4-MgS/Fe system. Notably, the dehydrogenation/hydrogenation of MgH2 has been significantly improved due to the synergistic catalysis of active species of Mg2Ni/Mg2NiH4, MgS and Fe originated from the MgH2-FeNi2S4 composite. The hydrogen absorption capacity of the MgH2-FeNi2S4 composite reaches to 4.02 wt% at 373 K for 1 h, a sharp contrast to the milled-MgH2 (0.67 wt%). In terms of dehydrogenation process, the initial dehydrogenation temperature of the composite is 80 K lower than that of the milled-MgH2, and the dehydrogenation activation energy decreases by 95.7 kJ·mol–1 compared with the milled-MgH2 (161.2 kJ·mol–1). This method provides a new strategy for improving the dehydrogenation/hydrogenation performance of the MgH2 material. © 2022

Hydrogen storage is a key link in hydrogen economy, where solid-state hydrogen storage is considered as the most promising approach because it can meet the requirement of high density and safety. Thereinto, magnesium-based materials (MgH2) are currently deemed as an attractive candidate due to the potentially high hydrogen storage density (7.6 wt%), however, the stable thermodynamics and slow kinetics limit the practical application.

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!014

Given its significant gravimetric hydrogen capacity advantage, lithium alanate (LiAlH4) is regarded as a suitable material for solid-state hydrogen storage. Nevertheless, its outrageous decomposition temperature and slow sorption kinetics hinder its application as a solid-state hydrogen storage material. This research’s objective is to investigate how the addition of titanium silicate (TiSiO4) altered the dehydrogenation behavior of LiAlH4. The LiAlH4–10 wt% TiSiO4 composite dehydrogenation temperatures were lowered to 92 °C (first-step reaction) and 128 °C (second-step reaction). According to dehydrogenation kinetic analysis, the TiSiO4-added LiAlH4 composite was able to liberate more hydrogen (about 6.0 wt%) than the undoped LiAlH4 composite (less than 1.0 wt%) at 90 °C for 2 h. After the addition of TiSiO4, the activation energies for hydrogen to liberate from LiAlH4 were lowered. Based on the Kissinger equation, the activation energies for hydrogen liberation for the two-step dehydrogenation of post-milled LiAlH4 were 103 and 115 kJ/mol, respectively. After milling LiAlH4 with 10 wt% TiSiO4, the activation energies were reduced to 68 and 77 kJ/mol, respectively. Additionally, the scanning electron microscopy images demonstrated that the LiAlH4 particles shrank and barely aggregated when 10 wt% of TiSiO4 was added. According to the X-ray diffraction results, TiSiO4 had a significant effect by lowering the decomposition temperature and increasing the rate of dehydrogenation of LiAlH4 via the new active species of AlTi and Si-containing that formed during the heating process. © 2023 by the authors.

Given its significant gravimetric hydrogen capacity advantage, lithium alanate (LiAlH4) is regarded as a suitable material for solid-state hydrogen storage. After milling LiAlH4 with 10 wt% TiSiO4, the activation energies were reduced to 68 and 77 kJ/mol, respectively.

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!015

The development of alloys that are hydrogenated and dehydrogenated quickly and actively at room temperature is a challenge for the safe and compact storage of hydrogen. In this study, a new high-entropy alloy (HEA) with AB-type configuration (A: hydride-forming elements, B: inert-to-hydrogen elements) was designed by considering valence electron concentration, electronegativity difference and atomic-size mismatch of elements. The alloy TiV2ZrCrMnFeNi had dual C14 Laves and BCC phases, in which C14 stored hydrogen and BCC/C14 interphase boundaries contributed to activation. The alloy absorbed 1.6 wt% of hydrogen at room temperature without any activation treatment and exhibited fast kinetics and full reversibility. © 2023 Acta Materialia Inc.

In this study, a new high-entropy alloy (HEA) with AB-type configuration (A: hydride-forming elements, B: inert-to-hydrogen elements) was designed by considering valence electron concentration, electronegativity difference and atomic-size mismatch of elements. The alloy absorbed 1.6 wt% of hydrogen at room temperature without any activation treatment and exhibited fast kinetics and full reversibility.

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!016

The metal-hydrogen interaction and its equilibrium conditions allow for distinct properties in metal hydrides (MHs). Based on these properties, MHs have been found to enable a range of novel technologies from thermal compression to sensors, and catalysis. Ni-MH batteries are currently the main application of hydrides in the market. However, new battery concepts such as Li-MgH2, Mn-MH, and hydride-based solid electrolytes have emerged. Fuel cells based on hydrides have also been proposed to convert the chemical “hydride energy” into electrical energy. Based on their unique thermodynamic properties, MHs are also the basis of new concepts in hydrogen compression, heat pumps, cooling systems, and thermal energy storage. Other important applications, including catalysis and chemical speciation have also been considered owing the chemical properties of hydrides. Sensors and smart mirrors based on the dynamic optical, structural, and electrical properties of MHs have been developed. This review summarizes current state-of-the-art along the multiple applications of MHs and provides recommendations on the future progress required to enable a more widespread adoption of MHs beyond their use as hydrogen storage materials. © 2022 Elsevier B.V.

The metal-hydrogen interaction and its equilibrium conditions allow for distinct properties in metal hydrides (MHs). Based on their unique thermodynamic properties, MHs are also the basis of new concepts in hydrogen compression, heat pumps, cooling systems, and thermal energy storage.

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!017

Solid state hydrogen storage addresses the problems of high pressurization in compressed gaseous state and energy intensive liquefaction in liquid state. Clathrate structures have shown promising results as host material for storing hydrogen as hydrate. The effect of different promoters on improving storage capabilities of clathrates have been studied at 263 K and 10 MPa hydrogen pressure. Hydrogen adsorption kinetics of four different clathrates using promoters Tetrahydrofuran, Tetrahydropyran, 1,3 Dioxolane and 2,3 Dihydrofuran with Multiwall Carbon nanotube as substrate was carried out. The results showed ∼1.5 wt% hydrogen adsorption within 90 min using CNT substrate. This is one of the first reports on usage of CNT as a substrate material for hydrogen storage in clathrate systems. It was observed that CNT shows synergitic effect in the hydrogen adsorption with fast kinetics (less than 90 min). The weight of substrate material (CNT) was also taken into consideration while calculating the weight % of hydrogen adsorption. The present study also involves design and simulation of a hydrogen storage canister (using CNT based clathrate) with embedded helical coolant coils on COMSOL Multiphysics software to analyse the effects of temperature management on improving hydrogen storage capability of the clathrate reactor bed. Results of simulation includes variation of hydrate concentration and temperature in clathrate reactor bed with the passage of time. The theoretical studies pave way for validating the scalability of clatharates as a viable hydrogen energy system. © 2022 Hydrogen Energy Publications LLC

Hydrogen adsorption kinetics of four different clathrates using promoters Tetrahydrofuran, Tetrahydropyran, 1,3 Dioxolane and 2,3 Dihydrofuran with Multiwall Carbon nanotube as substrate was carried out. It was observed that CNT shows synergitic effect in the hydrogen adsorption with fast kinetics (less than 90 min).

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!018

The increasing energy demand and the worldwide energy crisis must be met in large part via the sustainable growth of hydrogen energy, since this economy is relied upon to provide clean and carbon-free energy carriers. It is anticipated that the growing demand for light and heavy fuel cell cars would stimulate the development of onboard solid-state hydrogen technology. The research here concentrates on the importance of various permeable substances such as polymers in general, metallic substances, and complex metal hydrides, even if Si nanostructures (SiNSs) have become known as the obvious contender for solid-state hydrogen storage systems. SiNSs have gained prominence as a leading candidate for solid-state hydrogen storage systems. Renowned for their high storage capacity, SiNSs, including silicon nanowires and quantum dots, exhibit promising potential in addressing challenges associated with traditional hydrogen storage methods, positioning them as a key player in advancing clean and efficient energy storage technologies. SiNSs play a crucial role in advancing solid-state hydrogen storage technology. SiNSs, including silicon nanowires and quantum dots, exhibit high storage capacity. Despite challenges like surface oxidation, SiNS holds promise for efficient hydrogen storage, contributing to the development of sustainable energy solutions and mitigating the environmental impact associated with conventional automotive technologies. We focus on the processes that result in permeable silicon, nanowires made of porous silicon, and Si quantum dots. This investigation elucidates the characteristics and patterns of hydrogen's aid, the value of hydrogen power in automobiles for reducing global warming occurrences, and the potential of using SiNSs for hydrogen storage in tandem with other forms of transition and alkali earth materials to meet these difficulties. It demonstrates how catalysts are critical to fixing the current reversibility and desorption problems with hydrogen energy storage. As a result of the analysis, energy suppliers and Si-based fuel cells may be better able to tailor their services to individual customers' needs, which might boost the growth of the hydrogen energy industry. © 2024 Elsevier Ltd

SiNSs have gained prominence as a leading candidate for solid-state hydrogen storage systems. It demonstrates how catalysts are critical to fixing the current reversibility and desorption problems with hydrogen energy storage.

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!019

Hydrogen plays a crucial role in the future energy landscape owing to its high energy density. However, finding an ideal storage material is the key challenge to the success of the hydrogen economy. Various solid-state hydrogen storage materials, such as metal hydrides, have been developed to realize safe, effective, and compact hydrogen storage. However, low kinetics and thermodynamic stability lead to a high working temperature and a low hydrogen sorption rate of the metal hydrides. Using scaffolds made from porous materials like silica to confine the metal hydrides is necessary for better and improved hydrogen storage. Therefore, this article reviews porous silica-based scaffolds as an ideal material for improved hydrogen storage. The outcome showed that confining the metal hydrides using scaffolds based on porous silica significantly increases their storage capacities. It was also found that the structural modifications of the silica-based scaffold into a hollow structure further improved the storage capacity and increased the affinity and confinement ability of the metal hydrides, which prevents the agglomeration of metal particles during the adsorption/desorption process. Hence, the structural modifications of the silica material into a fibrous and hollow material are recommended to be crucial for further enhancing the metal hydride storage capacity. © 2023 Wiley-VCH GmbH.

Using scaffolds made from porous materials like silica to confine the metal hydrides is necessary for better and improved hydrogen storage. Therefore, this article reviews porous silica-based scaffolds as an ideal material for improved hydrogen storage.

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!020

This study describes the hydrogen storage performance of NaAlH4 with the addition of CuFe2O4 additive. The results were compared with undoped NaAlH4. For the first and second steps of dehydrogenation, the CuFe2O4-doped NaAlH4 liberated hydrogen at 150 °C and 220 °C, whereas as-milled NaAlH4 released hydrogen at 190 °C and 290 °C, respectively. The desorption kinetic analysis unveiled that the doped system liberated around 1.5 and 4.4 wt% hydrogen within 120 min at 150 and 200 °C, respectively. Meanwhile, the undoped NaAlH4 only desorbed 0.5 and 3.6 wt% hydrogen, respectively, under identical conditions. The activation energy for the doped system at the first step of dehydrogenation was decreased from 114.7 to 92.5 kJ/mol, while reduced from 125.2 to 98.1 kJ/mol at the second stage. The synergistic impact between the in-situ formed Cu2O and Fe during the heating process indicated that these active species are superior in boosting the hydrogen storage performance of NaAlH4. © 2023 Hydrogen Energy Publications LLC

The desorption kinetic analysis unveiled that the doped system liberated around 1.5 and 4.4 wt% hydrogen within 120 min at 150 and 200 °C, respectively. Meanwhile, the undoped NaAlH4 only desorbed 0.5 and 3.6 wt% hydrogen, respectively, under identical conditions.

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!021

The growing demand for energy and the need to reduce the carbon footprint has made green hydrogen a promising alternative to traditional fossil fuels. Green hydrogen is produced using renewable energy sources, making it a sustainable and environmentally friendly energy source. Solid-state hydrogen storage aims to store hydrogen in a solid matrix, offering potential advantages such as higher safety and improved energy density compared to traditional storage methods such as compressed gas or liquid hydrogen. However, the development of efficient and economically viable solid-state storage materials is still a challenge, and research continues in this field. Borophene is a two-dimensional material that offers potential as an intermediate hydrogen storage material due to its moderate binding energy and reversible behavior. Its unique geometry and electronic properties also allow for higher hydrogen adsorption capacity than metal-based complex hydrides, surpassing the goals set by the U.S. Department of Energy. Borophene has shown great potential for hydrogen storage, but it is still not practical for commercial use. In this review, borophene nanomaterials chemical and physical properties are discussed, related to hydrogen storage and binding energy. The importance of borophene for hydrogen storage, the challenges it faces, and its future prospects are also being discussed. © 2023 The Author(s)

Borophene is a two-dimensional material that offers potential as an intermediate hydrogen storage material due to its moderate binding energy and reversible behavior. Its unique geometry and electronic properties also allow for higher hydrogen adsorption capacity than metal-based complex hydrides, surpassing the goals set by the U.S. Department of Energy.

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!022

Magnesium hydride is considered as a promising solid-state hydrogen storage material due to its high hydrogen capacity. How to improve hydrogen desorption kinetics of MgH2 is one of key issues for its practical applications. In this study, we synthesize a Mg–Ni–TiS2 composite through a solution-based synthetic strategy. In the as-prepared composite, the co-precipitated Mg and Ni nanoparticles are highly dispersed on TiS2 nanosheets. As a result, the activation energy for hydrogen desorption decreases to 79.4 kJ mol−1. Meanwhile, the capacity retention rate is kept at the level of 98% and only slight kinetic deterioration is caused after fifty hydrogenation-dehydrogenation cycles. Further investigation indicates that the superior hydrogen desorption kinetics is attributed to the synergistically catalytic effect of the in situ formed Mg2NiH4 and TiH2, and the remained TiS2. The excellent cycle stability is related not only to the inhibition effect of the secondary phases on powder agglomeration and crystallite growth of Mg and MgH2 but also to the prevention effect of MgS and TiS2 on redistribution of catalytic Mg2NiH4 and TiH2 nanoparticles during cycling. This work introduces a feasible approach to develop Mg-based hydrogen storage materials. © 2023 Hydrogen Energy Publications LLC

As a result, the activation energy for hydrogen desorption decreases to 79.4 kJ mol−1. This work introduces a feasible approach to develop Mg-based hydrogen storage materials.

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!023

For hydrogen to be successfully used as an energy carrier in a new renewable energy driven economy, more efficient hydrogen storage technologies have to be found. Solid-state hydrogen storage in complex metal hydrides, such as sodium alanate (NaAlH4), is a well-researched candidate for this application. A series of NaAlH4/mesoporous carbon black composites, with high NaAlH4 content (50–90 wt%), prepared via ball milling have demonstrated significantly lower dehydrogenation temperatures with intense dehydrogenation starting at ∼373 K compared to bulk alanate's ≥ 456 K. Dehydrogenation/hydrogenation cycling experiments have demonstrated partial hydrogenation at 6 MPa H2 and 423 K. The cycling experiments combined with temperature-programmed dehydrogenation and powder X-ray diffraction have given insight into the fundamental processes driving the H2 release and uptake in the NaAlH4/carbon composites. It is established that most of the hydrogenation behavior can be attributed to the Na3AlH6 ↔ NaH transition. © 2023 The Authors

Solid-state hydrogen storage in complex metal hydrides, such as sodium alanate (NaAlH4), is a well-researched candidate for this application. A series of NaAlH4/mesoporous carbon black composites, with high NaAlH4 content (50–90 wt%), prepared via ball milling have demonstrated significantly lower dehydrogenation temperatures with intense dehydrogenation starting at ∼373 K compared to bulk alanate's ≥ 456 K. Dehydrogenation/hydrogenation cycling experiments have demonstrated partial hydrogenation at 6 MPa H2 and 423 K. The cycling experiments combined with temperature-programmed dehydrogenation and powder X-ray diffraction have given insight into the fundamental processes driving the H2 release and uptake in the NaAlH4/carbon composites.

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!024

Hypothesis: With increased development and electricity generation, great care to energy storage systems is crucial to overcome the discontinuity in the renewable production. Hydrogen is an ideal energy carrier for near future mobility, like automotive applications. Solid-state hydrogen storage materials including nanomaterials and layered systems are the key enablers to the future energy needs. However, the current materials are unable to meet all requirements in the storage capacity and commercialization. The hydrogen storage mechanisms (physical and chemical) are the key-points addressing the shortcomings in hydrogen absorption/adsorption in the interlayer space or on the surface of the material. All above require strategy for designing new hydrogen storage materials. Experiments: This review lays the recent foundations in the materials suitable for hydrogen storage particularly alloys, mixed metal oxides (MMOs), and their respective nanocomposites. Alloys and MMOs are two classes of materials with high discharge capacities, appropriate electrochemical performances, chemical stability, easy production pathways, and almost low cost. In the same vein, highly porous materials with a large surface area such as metal organic frameworks (MOFs), MXenes and carbon materials are thermodynamically and kinetically more favorable. Findings: The literature review illustrates that it is crucial to develop new materials with large-surface area, homogeneous texture, active-conductive profiles, large oxygen vacancies and low-cost. Multiphase materials (nanocomposites/hybrids) composed of at least two of above-mentioned materials can meet the established requirements in this field. Also, the present paper demonstrates a general overview of promoted understanding of hydrogen storage mechanisms on alloy/MMOs-based compounds in the energy storage systems. It is hoped that these observations pave the potential exploration directions to dominate imminent challenges in solid-state hydrogen storage. © 2023 Elsevier Ltd

Findings: The literature review illustrates that it is crucial to develop new materials with large-surface area, homogeneous texture, active-conductive profiles, large oxygen vacancies and low-cost. It is hoped that these observations pave the potential exploration directions to dominate imminent challenges in solid-state hydrogen storage.

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!025

As global energy consumption is rapidly climbing to maximum, fossil fuel resources face depletion on a global scale. The rapid depletion and higher energy demand consequences an escalation of energy prices originating from conventional sources as well as the release of greenhouse gases into the environment. Hydrogen as an alternative energy source merged as an ideal candidate, distinguished by its remarkable attributes and manifold advantages. It has an exceptional energy density of 120 MJ/kg and encompasses non-toxicity, sustainability, and a favorable environmental profile. Renewable and non-renewable sources can produce hydrogen and have versatile applications in transportation, power generation via fuel cells, and other industrial processes. Beyond having these advantages hydrogen has the benefits of energy security and can be produced locally. Nevertheless, commercial hydrogen has exceptionally low volumetric density under standard conditions which is the major obstacle in the way of its development. To cater this issue and to enhance its economic feasibility, two well-established methodologies are used by alterations in temperature and/or pressure conditions which facilitate the storage of hydrogen either in a pressurized gas or a cryogenic liquid. However, both methods incur energy consumption and pose safety concerns and complexity in the system, which raises the question of having other storage solutions. An emerging technology based on Solid-state hydrogen storage systems has recently gained substantial attention because of its high storage capacity and relatively mild temperature and pressure requirements. However, this technology is not yet mature enough because it doesn't fulfil the requirements to be implemented for industrial applications. But, intensive research in this field is underway to develop novel materials with enhanced performance at both the material and the system level. The current review report is focused on a comprehensive and in-depth comparative analysis of various hydrogen storage methods, with a major focus on the enhancement of the performance of the material which is suitable for solid-state hydrogen storage applications. © 2023 Hydrogen Energy Publications LLC

Beyond having these advantages hydrogen has the benefits of energy security and can be produced locally. However, this technology is not yet mature enough because it doesn't fulfil the requirements to be implemented for industrial applications.

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!026

Exceptionally porous crystals with ultrahigh adsorption capacities, metal–organic frameworks (MOFs), have received recognition as leading candidates for the promotion of solid-state hydrogen storage. MOFs are compelling adsorbents given their impressive uptake under stringent cryogenic and high-pressure conditions for physisorption. The use of high-throughput screening to rapidly identify potential candidates, the understanding of structure–property correlations through molecular simulations, and the use of machine learning to predict material properties offer a more efficient approach to meeting these stringent operational constraints. Furthermore, the open metal sites and customizable pore structures act make MOFs as catalysts or nanoconfinement matrices, facilitating enhancements in the thermodynamics and kinetics of reactive chemical hydrides. Strategically harnessing the tunability of MOFs could unlock vast, untapped potential for enabling high-density, reversible hydrogen storage under real-world conditions, aligned with sustainability needs. This review establishes MOFs as an innovative platform in solid-state hydrogen storage by intertwining material discovery with engineering principles. The comprehensive analysis and consolidation of the research provides new perspectives to broaden the scope of the investigation and drive the widespread deployment and development of hydrogen energy. © 2024 Elsevier B.V.

Exceptionally porous crystals with ultrahigh adsorption capacities, metal–organic frameworks (MOFs), have received recognition as leading candidates for the promotion of solid-state hydrogen storage. Strategically harnessing the tunability of MOFs could unlock vast, untapped potential for enabling high-density, reversible hydrogen storage under real-world conditions, aligned with sustainability needs.

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!027

Hydrogen is regarded as one of the most promising energy sources of the future, due to its low-cost, zero-pollution, and high-heat value. Nevertheless, traditional methods of storing hydrogen are commonly accompanied by the risk of leaks and explosions, so how to store and transport hydrogen safely and efficiently is a critical issue that needs to be addressed. Solid-state hydrogen storage is the most attractive way to store hydrogen in nanomaterials by chemical or physical adsorption, which has the advantages of high energy density and good safety. Here, a rational Ni-Zn bimetallic MOF has been constructed by a straightforward synthetic technique, in which the Zn atom was partially replaced by the Ni atom. The micropore rate of the Ni-Zn bimetallic MOFs is higher than that of ZIF-8. In addition, the presence of Ni provides more unsaturated metal sites and strengthens the bonding between hydrogen molecules and Ni, effectively improving the hydrogen storage capacity of Ni-Zn bimetallic MOFs. The experimental results show that the hydrogen adsorption capacity of Ni-Zn bimetallic MOFs can reach 1.35 wt% at 77 K and 1 bar. © 2023 The Royal Society of Chemistry.

Solid-state hydrogen storage is the most attractive way to store hydrogen in nanomaterials by chemical or physical adsorption, which has the advantages of high energy density and good safety. Here, a rational Ni-Zn bimetallic MOF has been constructed by a straightforward synthetic technique, in which the Zn atom was partially replaced by the Ni atom.

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!028

Hydrazine borane (N2H4BH3) has attracted considerable interest as a promising solid-state hydrogen storage material owing to its high hydrogen content and easy preparation. In this work, pressure-induced phase transitions of N2H4BH3 were investigated using a combination of vibrational spectroscopy, X-ray diffraction, and density functional theory (DFT) up to 30 GPa. Our results showed that N2H4BH3 exhibits remarkable structural stability in a very broad pressure region up to 15 GPa, and then two phase transitions were identified: the first one is from the ambient-pressure Pbcn phase to a Pbca phase near 15 GPa; the second is from the Pbca phase to a Pccn phase near 25 GPa. As revealed by DFT calculations, the unusual stability of N2H4BH3 and the late phase transformations were attributed to the pressure-mediated evolutions of dihydrogen bonding frameworks, the compressibility and the enthalpies of the high-pressure polymorphs. Our findings provide new insight into the structures and bonding properties of N2H4BH3 that are important for hydrogen storage applications. © 2023 The Royal Society of Chemistry.

In this work, pressure-induced phase transitions of N2H4BH3 were investigated using a combination of vibrational spectroscopy, X-ray diffraction, and density functional theory (DFT) up to 30 GPa. Our findings provide new insight into the structures and bonding properties of N2H4BH3 that are important for hydrogen storage applications.

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!029

Magnesium hydride has great potential for solid-state hydrogen storage. However, high dehydrogenation temperature and sluggish hydrogen absorption and desorption kinetics restrict its on-board automotive application. Hydrogen desorption from MgH2 is accompanied by the formation of Mg/MgH2 interfaces, which may play a key role in the further dehydrogenation process. In this work, first principles methods were used to understand the structural, electronic, energetic and hydrogen diffusion kinetic properties of pure and Ti-doped Mg(0001)/MgH2(110) interfaces. It is found that Ti interface doping can slightly increase the interfacial stability as revealed by the work of adhesion, interface energy and electronic structure. Additionally, for both the pure and Ti-doped Mg(0001)/MgH2(110) interfaces, the removal energies for the H atoms in the interface zone are significantly low compared with that of bulk MgH2. In terms of H mobility, the Ti dopant is beneficial for H atoms migrating from the inner layers to the interface for aggregation. Furthermore, hydrogen desorption from the two interfaces mainly takes place by hydrogen diffusion within the interface rather than across the interface into the Mg matrix, and Ti doping can enhance this process significantly. These theoretical observations for hydrogen diffusion behavior at the interface are further validated by fitting the isothermal dehydrogenation curves of MgH2-Ti with a series of kinetic models. © 2023 The Royal Society of Chemistry.

It is found that Ti interface doping can slightly increase the interfacial stability as revealed by the work of adhesion, interface energy and electronic structure. These theoretical observations for hydrogen diffusion behavior at the interface are further validated by fitting the isothermal dehydrogenation curves of MgH2-Ti with a series of kinetic models.

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!030

MgH2, a solid-state hydrogen storage material with high storage capacity, is facing the obstacles of high thermodynamic stability and slow reaction kinetics. Herein, different Vanadium (V) based catalysts (V2O5, Fe–V and V–Ni oxides) were synthesized by a hydrothermal method and ball milled with MgH2 to modify its hydrogen storage property. It is observed that the dehydrogenation performance (initial dehydrogenation temperature and desorption rate) of Fe–V oxide doped MgH2 was the best, followed by V2O5 and V–Ni oxide modified systems. The MgH2+7 wt% Fe–V composite exhibited an onset dehydrogenation temperature of 200 °C, 128 °C lower compared with the original MgH2. The absorption performance of MgH2 was also greatly enhanced by Fe–V oxide. The 7 wt% Fe–V modified MgH2 after dehydrogenation began to charge hydrogen from 25 °C to 5.1 wt% hydrogen was absorbed at 150 °C. The activation energy for hydrogen uptake of MgH2 was reduced from 76.5 ± 3.4 kJ/mol to 41.2 ± 4.7 kJ/mol. Additionally, the MgH2+7 wt% Fe–V composite maintained 97.2% hydrogen capacity after10 cycles. Our work here proves that elements substitution is a feasible way to tune the catalytic effect of oxides and may shed light on designing catalysts with higher activation in the future. © 2022 Elsevier Ltd

The activation energy for hydrogen uptake of MgH2 was reduced from 76.5 ± 3.4 kJ/mol to 41.2 ± 4.7 kJ/mol. Our work here proves that elements substitution is a feasible way to tune the catalytic effect of oxides and may shed light on designing catalysts with higher activation in the future.

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!031

In the burgeoning field of hydrogen energy, compositionally complex alloys promise unprecedented solid-state hydrogen storage applications. However, compositionally complex alloys are facing one main challenge: reducing alloy density and increasing hydrogen storage capacity. Here, we report TiMgLi-based compositionally complex alloys with ultralow alloy density and significant room-temperature hydrogen storage capacity. The record-low alloy density (2.83 g cm−3) is made possible by multi-principal-lightweight element alloying. Introducing multiple phases instead of a single phase facilitates obtaining a large hydrogen storage capacity (2.62 wt% at 50 °C under 100 bar of H2). The kinetic modeling results indicate that three-dimensional diffusion governs the hydrogenation reaction of the current compositionally complex alloys at 50 °C. The here proposed approach broadens the horizon for designing lightweight compositionally complex alloys for hydrogen storage purposes. © 2023 Elsevier Ltd

However, compositionally complex alloys are facing one main challenge: reducing alloy density and increasing hydrogen storage capacity. Here, we report TiMgLi-based compositionally complex alloys with ultralow alloy density and significant room-temperature hydrogen storage capacity.

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!032

Solid-state hydrogen storage is a promising roadmap for the safe and efficient utilization of hydrogen energy due to its moderate operating environment and high hydrogen storage density. However, as a representative solid-state hydrogen storage material, magnesium hydride (MgH2) is significantly limited in the commercial application due to its sluggish kinetics in the dehydrogenation process. Single-atom catalysts are a promising solution to this dilemma. However, the promising graphene-based single-atom catalysts are not yet sufficient to meet the dehydrogenation needs in engineering. To further address this dilemma, we designed a novel γ-graphyne based single-atom catalysts including eight 3d transition metals for promoting the dehydrogenation process of MgH2. Through using spin-polarized density functional theory calculations, we found that the energy barrier for MgH2 dehydrogenation has been significantly reduced even to 0.70 eV, which is far lower than the current graphene-based single-atom catalyst. In detail, the migration trajectory of hydrogen atom in the dehydrogenation process has been observed and confirmed using the ab initio molecular dynamics simulations. To investigate the intrinsic origin for its high catalytic activity of single-atom catalyst, we analyze the H[sbnd]Mg bond activation mechanism through the electron localization function, charge density difference and crystal orbital Hamiltonian population. Finally, we found the relationship between energy barrier with electronic structure of single-atom catalyst, such as electrostatic potential and system electronegativity. This work can not only provide new ideas for the optimize of dehydrogenation catalyst, but also lay a theoretical foundation for the design of novel energy storage material. © 2023 Elsevier Ltd

To further address this dilemma, we designed a novel γ-graphyne based single-atom catalysts including eight 3d transition metals for promoting the dehydrogenation process of MgH2. Finally, we found the relationship between energy barrier with electronic structure of single-atom catalyst, such as electrostatic potential and system electronegativity.

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!033

Researchers have focused on nanostructure materials in the last decade, which can play an essential role in storing hydrogen gas. Hydrogen is a future source of energy, having handling and storage challenges. In the new generation, solid-state materials have been used to store hydrogen gas as a metal hydride. Based on materials properties, Mg hydride is the most promising material to store hydrogen in a solid-state material. The theoretical hydrogen storage capacity of magnesium hydride is 7.6 wt% making it a more suitable material for hydrogen storage in the future. Instead of having high storage capacity, magnesium's practical application as a hydride is limited due to its low kinetics and high working temperature. Aside from the less thermo-stability of bulk MgH2, to achieve the maximum hydrogen storage capacity the decomposition required a higher temperature of about 300 °C with 1 bar pressure. As a result, it is necessary to optimize the stability of hydrogen and magnesium molecules to enhance kinetic and thermodynamic properties. The critical factors in improving hydrogenation properties are decreasing particle size (nano-scale) and adding various catalysts. © 2023 Elsevier Ltd. All rights reserved.

In the new generation, solid-state materials have been used to store hydrogen gas as a metal hydride. The critical factors in improving hydrogenation properties are decreasing particle size (nano-scale) and adding various catalysts.

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!034

In this study, structural, mechanical, electronic, dynamic, thermodynamic and hydrogen storage properties of MgX3H8 (X = Sc, Ti, Zr) were investigated by means of density functional theory which was not studied/reported experimentally or theoretically in the previous literature. This is the first thorough study about various properties of these materials. These materials were considered as promising potential host materials for solid state hydrogen storage. The evaluation of computed formation enthalpies of MgX3H8 (X = Sc, Ti, Zr), elastic constants, and phonon dispersion graphs revealed that MgX3H8 (X = Sc, Ti, Zr) is thermodynamically, mechanically, and dynamically stable and synthesizable. The analysis of B/G ratio, Cp and Poisson's ratio showed that MgSc3H8 is a brittle material whereas MgTi3H8 and MgZr3H8 are ductile materials. Moreover, anisotropy factor, machinability index, hardness, melting and Debye temperature of the materials were obtained and analysed in depth. The electronic band structures of MgX3H8 (X = Sc, Ti, Zr) illustrated metallic character since the bands (valence and conduction) intersect the Fermi level along the main symmetry directions. The phonon dispersion curves, and the partial state densities of the materials have positive frequencies, therefore, materials are dynamically stable in the cubic structure. The gravimetric hydrogen densities were calculated as 4.60 wt% for MgSc3H8, 4.38 wt% for MgTi3H8 and 2.56 wt% for MgZr3H8. The hydrogen desorption temperatures were computed as 239.54 K for MgSc3H8, 241.76 K for MgTi3H8 and 303.87 K for MgZr3H8. The mechanical properties of the materials suggest that they can be promising host materials for hydrogen storage. © 2024 Elsevier Ltd

In this study, structural, mechanical, electronic, dynamic, thermodynamic and hydrogen storage properties of MgX3H8 (X = Sc, Ti, Zr) were investigated by means of density functional theory which was not studied/reported experimentally or theoretically in the previous literature. This is the first thorough study about various properties of these materials.

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!035

Solid-state hydrogen storage materials are safe and lightweight hydrogen carriers. Among the various solid-state hydrogen carriers, hydrogen boride (HB) sheets possess a high gravimetric hydrogen capacity (8.5 wt%). However, heating at high temperatures and/or strong ultraviolet illumination is required to release hydrogen (H2) from HB sheets. In this study, the electrochemical H2 release from HB sheets using a dispersion system in an organic solvent without other proton sources is investigated. H2 molecules are released from the HB sheets under the application of a cathodic potential. The Faradaic efficiency for H2 release from HB sheets reached >90%, and the onset potential for H2 release is −0.445 V versus Ag/Ag+, which is more positive than those from other proton sources, such as water or formic acid, under the same electrochemical conditions. The total electrochemically released H2 in a long-time experiment reached ≈100% of the hydrogen capacity of HB sheets. The H2 release from HB sheets is driven by a small bias; thus, they can be applied as safe and lightweight hydrogen carriers with economical hydrogen release properties. © 2024 The Authors. Small published by Wiley-VCH GmbH.

However, heating at high temperatures and/or strong ultraviolet illumination is required to release hydrogen (H2) from HB sheets. The H2 release from HB sheets is driven by a small bias; thus, they can be applied as safe and lightweight hydrogen carriers with economical hydrogen release properties.

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!036

Lithium is a popular lightweight material in the field of energy storage because of its hydrogen-binding properties and electrochemical advantages. The high hydrogen uptake capacity (∼12.6 wt%) of lithium hydride (LiH) is limited by the major thermodynamic constraint of requiring a higher temperature (∼700 °C) for desorption at 0.1 MPa. Incorporating a third element that creates Li phases during LiH dehydrogenation can help overcome thermodynamic constraints. This study involves modifying the hydrogen storage properties and thermodynamic characteristics of LiH through mechanical alloying with porous silicon (PS). Pressure composition isotherms measure the reversible hydrogen storage capacity (∼3.39 wt%) of LiH-PS alloy at different temperatures. The energy of hydrogen interaction is quantified by isosteric heat of absorption, which provides the enthalpy change in the reaction system. Hydrogen absorption and desorption enthalpies of 94.5 kJ (mol H2)−1 and 114.9 kJ (mol H2)−1 demonstrate the lowest energy demand among previously reported LiH alloys. The energy of hydrogen interaction is quantified by isosteric heat of absorption, which provides the enthalpy change in the reaction system. The hydride decomposition of the alloy indicates the possible range of hydrogen desorption. © 2023 Hydrogen Energy Publications LLC

This study involves modifying the hydrogen storage properties and thermodynamic characteristics of LiH through mechanical alloying with porous silicon (PS). Pressure composition isotherms measure the reversible hydrogen storage capacity (∼3.39 wt%) of LiH-PS alloy at different temperatures.

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!037

This investigation explores the solid-state hydrogen storage properties of two series of hydrogen storage alloys: (Ti0.85Zr0.15)xMn0.8CrFe0.2 (x = 1.00∼1.10) and (Ti0.85Zr0.15)1.02MnyCr1.8-yFe0.2 (y = 1.00∼0.40) alloys. These alloys exhibit a single C14-Laves phase structure and demonstrate promising capabilities for solid-state hydrogen storage. The (Ti0.85Zr0.15)xMn0.8CrFe0.2 (x = 1.00∼1.10) alloys display an increased hydrogen absorption capacity and a reduced plateau pressure at higher super-stoichiometric ratios of x. When x = 1.10, the alloy achieves a maximum capacity of 1.86 wt%. The hydrogen storage capacity of the (Ti0.85Zr0.15)1.02MnyCr1.8-yFe0.2 (y = 1.00∼0.40) alloys diminishes as the value of y decreases. Furthermore, the hydrogen absorption plateau pressure and hysteresis factor of the alloys increase with an escalating Mn/Cr ratio. The analysis of cyclic stability reveals that the primary factor contributing to poor cycling stability of the (Ti0.85Zr0.15)1.02Mn0.4Cr1.4Fe0.2 alloy is the compositional decomposition, rather than pulverization or alterations in the phase structure. In summary, this investigation enhances our understanding of the solid-state hydrogen storage properties of these alloys. It establishes a foundation for further research and development in this pivotal field of hydrogen storage. © 2023 Hydrogen Energy Publications LLC

These alloys exhibit a single C14-Laves phase structure and demonstrate promising capabilities for solid-state hydrogen storage. It establishes a foundation for further research and development in this pivotal field of hydrogen storage.

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!038

Hydrogen storage and transportation technology is the key part that affects the large-scale and commercial application of hydrogen energy, and it is also an important factor that influences the future development pattern of the world clean energy industry. Compared with several current hydrogen storage and transportation technologies, solid-state hydrogen storage technology plays an important role in the field of hydrogen storage and transportation with its high quality density and high safety. Starting from the principles of hydrogen storage based on chemical adsorption mechanism, the research progress and status quo of different solid-state hydrogen storage materials are introduced. From the perspective of raw materials, technology maturity, research projects and the number of patents, the development prospect of solid-state hydrogen storage technology in the future is analyzed. © 2023 Editorial Office of P.R.E.. All rights reserved.

Compared with several current hydrogen storage and transportation technologies, solid-state hydrogen storage technology plays an important role in the field of hydrogen storage and transportation with its high quality density and high safety. Starting from the principles of hydrogen storage based on chemical adsorption mechanism, the research progress and status quo of different solid-state hydrogen storage materials are introduced.

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!039

Solid-state hydrogen storage is gradually becoming an effective way for the large-scale storage and transportation of hydrogen energy. Magnesium hydride (MgH2) has become a promising candidate among solid-state hydrogen storage materials due to its high hydrogen storage density, low cost and good safety. However, ambiguous H-Mg bond weakening mechanism of various catalysts on MgH2 hinders the development of novel catalysts for MgH2 dehydrogenation. To overcome this problem, we applied the model catalyst, single-atom catalyst with accurately characterizable coordination structure, to understand the interaction between catalyst and MgH2 surface through spin-polarized density-functional theory calculation. We constructed heterogeneous interface structures between single-atom catalysts and MgH2 surface including nine kinds of transition metal atoms. The interaction between single-atom catalysts and MgH2 surface has been well explored through bond length, electron localization function, charge density difference and crystal orbital Hamiltonian population, providing the intrinsic information of H-Mg bond weakening mechanism over single-atom catalysts. This work can establish the foundational guide for the design of novel dehydrogenation catalysts. © 2024, The Author(s).

We constructed heterogeneous interface structures between single-atom catalysts and MgH2 surface including nine kinds of transition metal atoms. The interaction between single-atom catalysts and MgH2 surface has been well explored through bond length, electron localization function, charge density difference and crystal orbital Hamiltonian population, providing the intrinsic information of H-Mg bond weakening mechanism over single-atom catalysts.

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!040

In the process of building a new power system with new energy sources as the mainstay, wind power and photovoltaic energy enter the multiplication stage with randomness and uncertainty, and the foundation and support role of large-scale long-time energy storage is highlighted. Considering the advantages of hydrogen energy storage in large-scale, cross-seasonal and cross-regional aspects, the necessity, feasibility and economy of hydrogen energy participation in long-time energy storage under the new power system are discussed. Firstly, power supply and demand production simulations were carried out based on the characteristics of new energy generation in China. When the penetration of new energy sources in the new power system reaches 45%, long-term energy storage becomes an essential regulation tool. Secondly, by comparing the storage duration, storage scale and application scenarios of various energy storage technologies, it was determined that hydrogen storage is the most preferable choice to participate in large-scale and long-term energy storage. Three long-time hydrogen storage methods are screened out from numerous hydrogen storage technologies, including salt-cavern hydrogen storage, natural gas blending and solid-state hydrogen storage. Finally, by analyzing the development status and economy of the above three types of hydrogen storage technologies, and based on the geographical characteristics and resource endowment of China, it is pointed out that China will form a hydrogen storage system of “solid state hydrogen storage above ground and salt cavern storage underground” in the future. © 2023 by the authors.

Firstly, power supply and demand production simulations were carried out based on the characteristics of new energy generation in China. Finally, by analyzing the development status and economy of the above three types of hydrogen storage technologies, and based on the geographical characteristics and resource endowment of China, it is pointed out that China will form a hydrogen storage system of “solid state hydrogen storage above ground and salt cavern storage underground” in the future.

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!041

Recently, high entropy alloys (HEAs) with body-centred cubic (BCC) single phase structures have attracted wide attention in many fields including hydrogen storage, due to their unique structural characteristics and excellent performance. Its novel design concept provides more possibilities for the investigation of advanced hydrogen storage materials, in which several remarkable research works have been published, providing opportunities for the design of hydrogen storage materials with unprecedented properties. In this review, we combed through the definition and criteria of high entropy alloys, and summarized the current research status of body-centred cubic-structured high entropy alloys for hydrogen storage from multiple perspectives of composition designs, synthesis processes, and hydrogen storage properties. Moreover, the possible application scenarios and future research directions are analysed. Copyright © 2023 Kong, Cheng, Wan and Xue.

Recently, high entropy alloys (HEAs) with body-centred cubic (BCC) single phase structures have attracted wide attention in many fields including hydrogen storage, due to their unique structural characteristics and excellent performance. Its novel design concept provides more possibilities for the investigation of advanced hydrogen storage materials, in which several remarkable research works have been published, providing opportunities for the design of hydrogen storage materials with unprecedented properties.

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!042

Sodium amide (NaNH2) in its α form is a common compound that has recently seen renewed interest, mainly for its potential use as a solid-state hydrogen storage material. In this work, we present a synergic theoretical and experimental characterization of the compound, including novel measured and simulated vibrational spectra (IR and Raman) and X-ray diffraction patterns. We put forward the hypothesis of a low-temperature symmetry breaking of the structure to space group C2/c, while space group Fddd is commonly reported in the literature and experimentally found down to 80 K. Additionally, we report a theoretical estimate of the heat of formation of sodium amide from ammonia to be equal to −12.2 kcal/mol at ambient conditions. © 2023 The Authors. Published by American Chemical Society

Sodium amide (NaNH2) in its α form is a common compound that has recently seen renewed interest, mainly for its potential use as a solid-state hydrogen storage material. We put forward the hypothesis of a low-temperature symmetry breaking of the structure to space group C2/c, while space group Fddd is commonly reported in the literature and experimentally found down to 80 K. Additionally, we report a theoretical estimate of the heat of formation of sodium amide from ammonia to be equal to −12.2 kcal/mol at ambient conditions.

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!043

Hydrogen energy has attracted a lot of interest as a renewable and sustainable energy source, but there are a few technical impediments associated with its storage. Solid-state hydrogen storage is a catching-on and intensively researched alternative to other methods for storing hydrogen. Perovskite hydrides exhibit the ability to store solid-state hydrogen safely and effectively. This work employs the first-principles calculations to investigate the physical properties of LiCaF3˗αHα (α = 0,1,2,3) perovskite compounds, aiming to elucidate insights into their potential in hydrogen storage applications. To assess the phase stability, we computed the formation enthalpies, which indicate that all compounds are stable and can be synthesized experimentally. Notably, the optimized lattice parameter decreased from 4.42 to 4.32 Å when an impurity was added to pristine material. Additionally, the evaluation of the elastic stiffness constants manifests that all LiCaF3-αHα compounds are mechanically stable and brittle in nature. Investigations of electronic properties demonstrate the narrowing in the bandgap of the host compound with the inclusion of H. To gain insight into how the absorption edge shifts towards the valence band and causes the band gap to diminish, the Burstein-Moss shift and band gap renormalization were investigated. Interestingly, the gravimetric and volumetric hydrogen storage capacities have been improved up to 6.04 wt% and 61.77 gH2l−1, respectively, which are fulfilling the target set by DOE for 2025. In short, this work suggests the applicability of LiCaH3 hydrides for effective hydrogen storage. © 2024 Elsevier Ltd

Perovskite hydrides exhibit the ability to store solid-state hydrogen safely and effectively. In short, this work suggests the applicability of LiCaH3 hydrides for effective hydrogen storage.

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!044

The high hydrogen storage capacity (10.5 wt.%) and release of hydrogen at a moderate temperature make LiAlH4 an appealing material for hydrogen storage. However, LiAlH4 suffers from slow kinetics and irreversibility. Hence, LaCoO3 was selected as an additive to defeat the slow kinetics problems of LiAlH4. For the irreversibility part, it still required high pressure to absorb hydrogen. Thus, this study focused on the reduction of the onset desorption temperature and the quickening of the desorption kinetics of LiAlH4. Here, we report the different weight percentages of LaCoO3 mixed with LiAlH4 using the ball-milling method. Interestingly, the addition of 10 wt.% of LaCoO3 resulted in a decrease in the desorption temperature to 70 °C for the first stage and 156 °C for the second stage. In addition, at 90 °C, LiAlH4 + 10 wt.% LaCoO3 can desorb 3.37 wt.% of H2 in 80 min, which is 10 times faster than the unsubstituted samples. The activation energies values for this composite are greatly reduced to 71 kJ/mol for the first stages and 95 kJ/mol for the second stages compared to milled LiAlH4 (107 kJ/mol and 120 kJ/mol for the first two stages, respectively). The enhancement of hydrogen desorption kinetics of LiAlH4 is attributed to the in situ formation of AlCo and La or La-containing species in the presence of LaCoO3, which resulted in a reduction of the onset desorption temperature and activation energies of LiAlH4. © 2023 by the authors.

Hence, LaCoO3 was selected as an additive to defeat the slow kinetics problems of LiAlH4. For the irreversibility part, it still required high pressure to absorb hydrogen.

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!045

Lithium aluminum hydride (LiAlH4) with a high hydrogen capacity of 10.5 wt% has become one of the most promising solid-state hydrogen storage materials for onboard hydrogen fuel cell systems. However, neither dehydrogenation kinetics nor cycling behaviors of LiAlH4 can fulfill the requirements of practical application. Here, we prepared the Ni/C nanoparticles anchored on large-size Ti3C2Tx nanosheets, firstly introduced into LiAlH4 to investigate its catalytic effect. Dehydrogenation experiments demonstrate that LiAlH4 doped with 7 wt% Ni/C@Ti3C2 starts to release hydrogen at 56.9 °C. Also, it can release about 4.3 wt% hydrogen within 50 min at 120 °C. The activation energies of LiAlH4 doped with 7 wt% Ni/C@Ti3C2 for the first and second steps are 34.5% and 53.2% lower than the as-received LiAlH4, respectively. Under 300 °C and 40 bar hydrogen, it can absorb 0.58 wt% hydrogen. It is found that in situ formed intermetallic Al2Ti during ball milling can weaken the Al-H bonds in LiAlH4 through interfacial charge transfer and the dehybridization, benefitting for the breaking of the Al-H bond in LiAlH4. In addition, Al2Ti can promote the adsorption and splitting of H2, contributing to the rehydrogenation of LiAlH4. © 2022 Elsevier B.V.

Here, we prepared the Ni/C nanoparticles anchored on large-size Ti3C2Tx nanosheets, firstly introduced into LiAlH4 to investigate its catalytic effect. Dehydrogenation experiments demonstrate that LiAlH4 doped with 7 wt% Ni/C@Ti3C2 starts to release hydrogen at 56.9 °C.

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!046

Solid-state storage of hydrogen molecules in carbon-based light metal single-atom materials is promising to achieve both high hydrogen storage capacity and uptake rate, but there is a lack of fundamental understanding and design principles to guide the rational design of the materials. Here, a theoretical relationship is established between the hydrogen capacity/rate and the structures of the heteroatom-doped-graphene-supported light metal Li single atom materials for high-efficient solid-state hydrogen storage, which is verified by combining spectroscopic characterization, H2 adsorption/desorption measurements, and density functional theory (DFT) calculations. Based on the DFT calculations, a novel descriptor Φ is developed to correlate the inherent properties of dopants with the hydrogen storage properties, and further to screen out the best dual-doped-graphene-supported light metal Li single-atom hydrogen storage materials. The dual-doped materials have a much higher hydrogen storage capability than the sole-doped ones and exceed the best carbon-based hydrogen storage materials so far. © 2024 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.

Solid-state storage of hydrogen molecules in carbon-based light metal single-atom materials is promising to achieve both high hydrogen storage capacity and uptake rate, but there is a lack of fundamental understanding and design principles to guide the rational design of the materials. Here, a theoretical relationship is established between the hydrogen capacity/rate and the structures of the heteroatom-doped-graphene-supported light metal Li single atom materials for high-efficient solid-state hydrogen storage, which is verified by combining spectroscopic characterization, H2 adsorption/desorption measurements, and density functional theory (DFT) calculations.

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!047

We present a machine learning (ML) framework HEART (HydrogEn storAge propeRty predicTor) for identifying suitable families of metal alloys for hydrogen storage under ambient conditions. Our framework includes two ML models that predict the hydrogen storage capacity (HYST) and the enthalpy of hydride formation (THOR) of multi-component metal alloys. We demonstrate that a chemically diverse set of features effectively describes the hydrogen storage properties of the alloys. In HYST, we use absorption temperature as a feature which improved H2wt% prediction significantly. For out-of-the-bag samples, HYST predicted H2wt% with R2 score of 0.81 and mean absolute error (MAE) of 0.45 wt% whereas R2 score is 0.89 and MAE is 4.53 kJ/molH2 for THOR. These models are further employed to predict H2wt% and ΔH for ∼ 6.4 million multi-component metal alloys. We have identified 6480 compositions with superior storage properties (H2wt% > 2.5 at room temperature and ΔH < 60 kJ/molH2). We have also discussed in detail the interesting trends picked up by these models like temperature dependent variation in the rate of hydrogenation and alloying effect on H2wt% and ΔH in different families of alloys. Importantly certain elements like Al, Si, Sc, Cr, and Mn when mixed in small fractions with hydriding elements like Mg, Ti, V etc. systematically reduce ΔH without significantly compromising the storage capacity. Further upon increasing the number of elements in the alloy i.e from binary to ternary to quaternary, the number of compositions with lower enthalpies also increases. From the 6.4 million compositions, we have reported new alloy families having potential for hydrogen storage at room temperature. Finally, we demonstrate that HEART has the potential to scan vast chemical spaces by narrowing down potential materials for hydrogen storage. © 2023 Hydrogen Energy Publications LLC

These models are further employed to predict H2wt% and ΔH for ∼ 6.4 million multi-component metal alloys. From the 6.4 million compositions, we have reported new alloy families having potential for hydrogen storage at room temperature.

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!048

Magnesium hydride (MgH2) is the most prominent carrier for storing hydrogen in solid-state mode. However, their slow kinetics and high thermodynamics become an obstacle in hydrogen storage. The present study elaborates on the catalytic effect of graphene (Gr) and vanadium disulfide (VS2) on MgH2 to enhance its hydrogen sorption kinetic. The temperature-programmed desorption study shows that the onset desorption temperature of MgH2 catalyzed by VS2 and MgH2 catalyzed by Gr is 289 °C and 300 °C, respectively. These desorption temperatures are 87 °C and 76 °C lower than the desorption temperature of pristine MgH2. The rapid rehydrogenation kinetics for the MgH2 catalyzed by VS2 have been found at a temperature of 300 °C under 15 atm H2 pressure by absorbing ∼4.04 wt% of hydrogen within 1 min, whereas the MgH2 catalyzed by Gr takes ∼3 min for absorbing the same amount of hydrogen under the similar temperature and pressure conditions. The faster release of hydrogen was also observed in MgH2 catalyzed by VS2 than MgH2 catalyzed by Gr and pristine MgH2. MgH2 catalyzed by VS2 releases ∼2.54 wt% of hydrogen within 10 min, while MgH2 catalyzed by Gr takes ∼30 min to release the same amount of hydrogen. Furthermore, MgH2 catalyzed by VS2 also persists in the excellent cyclic stability and reversibility up to 25 cycles. © 2022 Hydrogen Energy Publications LLC

Magnesium hydride (MgH2) is the most prominent carrier for storing hydrogen in solid-state mode. Furthermore, MgH2 catalyzed by VS2 also persists in the excellent cyclic stability and reversibility up to 25 cycles.

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!049

The solid-state hydrogen storage in metal hydride (MH) is safer and energy efficient than the gaseous and liquid storage methods. The absorption of hydrogen in MH is highly exothermic. Hence, a good heat management system is required to increase the charging rate. The phase change material (PCM) can be integrated into the reactor to reuse the absorption heat for hydrogen desorption. The present numerical study models the concentric cylindrical reactor with magnesium (Mg) as MH surrounded by sodium nitrate (NaNO3) as PCM using COMSOL Multiphysics v6.1. The effect of buoyancy inside the PCM domain is investigated. An iterative approach is used to determine the required amount of PCM. Copper fins are added inside both MH and PCM. The effect of the number of fins, corresponding fin thickness and pitch on hydrogen absorption are determined to optimize the MH reactor. The outcomes reveal that the hydrogen absorption rate increases with fin numbers. The reactor with 10 and 30 fins takes 86.5 and 97.3 % less time than without fins for 90 % hydrogen absorption, respectively. The novel approach is proposed to estimate the fin efficiency (ηf) using temperature profiles of MH and fin during prevailing unsteady heat and mass transfer. The fin factor (Ff) is presented using the ηf and mass of MH. The performance evaluation criterion (PEC) is discussed based on hydrogen absorption relative to the system's weight. Further, the effect of operating parameters like hydrogen supply pressure and the initial temperature is studied on the reactor performance. © 2023 Elsevier Ltd

Hence, a good heat management system is required to increase the charging rate. An iterative approach is used to determine the required amount of PCM.

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!050

Complex aluminum hydrides with high hydrogen capacity are among the most promising solid-state hydrogen storage materials. The present study determines the thermal stability, hydrogen dissociation energy, and electronic structures of alkali metal aluminum hydrides, MAlH4 (M = Li, Na, K, and Cs), using first-principles density functional theory calculations in an attempt to gain insight into the dehydrogenation mechanism of these hydrides. The results show that the hydrogen dissociation energy (Ed-H2) of MAlH4 (M = Li, Na, K, and Cs) correlates with the Pauling electronegativity of cation M (χP); that is, the Ed-H2 (average value) decreases, i.e., 1.211 eV (LiAlH4) < 1.281 eV (NaAlH4) < 1.291 eV (KAlH4) < 1.361 eV (CsAlH4), with the increasing χP value, i.e., 0.98 (Li) > 0.93 (Na) > 0.82 (K) > 0.79 (Cs). The main reason for this finding is that alkali alanate MAlH4 at higher cation electronegativity is thermally less stable and held by weaker Al-H covalent and H-H ionic interactions. Our work contributes to the design of alkali metal aluminum hydrides with a favorable dehydrogenation, which is useful for on-board hydrogen storage. © 2023 by the authors.

The main reason for this finding is that alkali alanate MAlH4 at higher cation electronegativity is thermally less stable and held by weaker Al-H covalent and H-H ionic interactions. Our work contributes to the design of alkali metal aluminum hydrides with a favorable dehydrogenation, which is useful for on-board hydrogen storage.

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!051

One of the ideal energy carriers for the future is hydrogen. It has a high energy density and is a source of clean energy. A crucial step in the development of the hydrogen economy is the safety and affordable storage of a large amount of hydrogen. Thus, owing to its large storage capacity, good reversibility, and low cost, Magnesium hydride (MgH2) was taken into consideration. Unfortunately, MgH2 has a high desorption temperature and slow ab/desorption kinetics. Using the ball milling technique, adding cobalt lanthanum oxide (LaCoO3) to MgH2 improves its hydrogen storage performance. The results show that adding 10 wt.% LaCoO3 relatively lowers the starting hydrogen release, compared with pure MgH2 and milled MgH2. On the other hand, faster ab/desorption after the introduction of 10 wt.% LaCoO3 could be observed when compared with milled MgH2 under the same circumstances. Besides this, the apparent activation energy for MgH2–10 wt.% LaCoO3 was greatly reduced when compared with that of milled MgH2. From the X-ray diffraction analysis, it could be shown that in-situ forms of MgO, CoO, and La2O3, produced from the reactions between MgH2 and LaCoO3, play a vital role in enhancing the properties of hydrogen storage of MgH2. © 2023 by the authors.

Thus, owing to its large storage capacity, good reversibility, and low cost, Magnesium hydride (MgH2) was taken into consideration. Besides this, the apparent activation energy for MgH2–10 wt.% LaCoO3 was greatly reduced when compared with that of milled MgH2.

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!052

Magnesium hydride (MgH2) attracts wide interests as a promising hydrogen energy carrier, but its commercial application is hampered by the high operating temperatures and slow dehydrogenation kinetics. Herein, CrMnFeCoNi and CrFeCoNi high-entropy alloys (HEAs) were adopted to boost the hydrogen storage performance of MgH2. It was demonstrated that the morphology of catalysts and addition of Mn had a great impact on the performance of HEAs catalysts. In particular, the Mn containing HEAs nanosheets presented the best performance. The MgH2-CrMnFeCoNi composite could release 6.5 wt% H2 in 10 min at 300 °C and started to absorb H2 at 40 °C. Moreover, kinetic analysis revealed that the rate control model in dehydrogenation process of HEA-4 modified MgH2 changed from permeation model of MgH2 to diffusion. In addition, 97% hydrogen storage volume could be maintained after 20 cycles at 300 °C, showing a good cycling performance. Microstructure analysis showed that the CrMnFeCoNi nanosheets were uniform dispersed over the surface of MgH2, bringing numerous heterogeneous activation sites to speed up the dispersal of hydrogen. Besides, the cocktail effect of HEAs exerted synergic action between Cr, Mn, Fe, Co and Ni elements to improve the overall catalytic efficiency. Therefore, the de/rehydrogeantion performance of the MgH2-CrMnFeCoNi composite was surprisingly accelerated. © 2023 Elsevier B.V.

Magnesium hydride (MgH2) attracts wide interests as a promising hydrogen energy carrier, but its commercial application is hampered by the high operating temperatures and slow dehydrogenation kinetics. In addition, 97% hydrogen storage volume could be maintained after 20 cycles at 300 °C, showing a good cycling performance.

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!053

Currently, magnesium hydride (MgH2) as a solid-state hydrogen storage material has become the subject of major research owing to its good reversibility, large hydrogen storage capacity (7.6 wt%) and affordability. However, MgH2 has a high decomposition temperature (>400 °C) and slow desorption and absorption kinetics. In this work, BaMnO3 was synthesized using the solid-state method and was used as an additive to overcome the drawbacks of MgH2. Interestingly, after adding 10 wt% of BaMnO3, the initial desorption temperature of MgH2 decreased to 282 °C, which was 138 °C lower than that of pure MgH2 and 61 °C lower than that of milled MgH2. For absorption kinetics, at 250 °C in 2 min, 10 wt% of BaMnO3-doped MgH2 absorbed 5.22 wt% of H2 compared to milled MgH2 (3.48 wt%). Conversely, the desorption kinetics also demonstrated that 10 wt% of BaMnO3-doped MgH2 samples desorbed 5.36 wt% of H2 at 300 °C within 1 h whereas milled MgH2 only released less than 0.32 wt% of H2. The activation energy was lowered by 45 kJ/mol compared to that of MgH2 after the addition of 10 wt% of BaMnO3. Further analyzed by using XRD revealed that the formation of Mg0·9Mn0·1O, Mn3O4 and Ba or Ba-containing enhanced the performance of MgH2. © 2023 Hydrogen Energy Publications LLC

Currently, magnesium hydride (MgH2) as a solid-state hydrogen storage material has become the subject of major research owing to its good reversibility, large hydrogen storage capacity (7.6 wt%) and affordability. In this work, BaMnO3 was synthesized using the solid-state method and was used as an additive to overcome the drawbacks of MgH2.

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!054

The complex hydride NaAlH4 remains the archetype hydrogen storage system. In this paper, we have explored the catalytic action of Al65Cu20Fe15 quasicrystal (QC) on the de/re-hydrogenation study of NaAlH4. The leached ball-milled Al65Cu20Fe15 (LBMACF) catalyzed NaAlH4 sample has shown a lower hydrogen desorption temperature (140 °C) than other catalyzed and uncatalyzed NaAlH4 samples. NaAlH4-LBMACF rapidly absorbed ∼3.20 wt% of hydrogen within 1 min and absorbed maximum capacity (∼4.68 wt%) in 15 min, while NaAlH4-LACF, NaAlH4-BMACF, NaAlH4-ACF, and pristine NaAlH4 absorbed only 0.50 wt%, 1.38 wt%, 1.10 wt%, and 0.70 wt% in 1 min at 130 °C under 100 atm hydrogen pressure. NaAlH4-LBMACF has desorbed ∼4.22 wt% of hydrogen within 15 min, while the same amount of hydrogen desorbed by NaAlH4-LACF takes 45 min at 130 °C under 1 atm hydrogen pressure. NaAlH4-LBMACF shows reversibility up to 25 cycles with minimum degradation of hydrogen storage capacity of ∼0.06 wt% during de/re-hydrogenation. The catalytic mechanism and catalytic effect of Al–Cu–Fe on the NaAlH4 have been discussed using structural, microstructural analysis, in-situ nuclear magnetic resonance (NMR) spectroscopy, in-situ Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). © 2022 Hydrogen Energy Publications LLC

The leached ball-milled Al65Cu20Fe15 (LBMACF) catalyzed NaAlH4 sample has shown a lower hydrogen desorption temperature (140 °C) than other catalyzed and uncatalyzed NaAlH4 samples. The catalytic mechanism and catalytic effect of Al–Cu–Fe on the NaAlH4 have been discussed using structural, microstructural analysis, in-situ nuclear magnetic resonance (NMR) spectroscopy, in-situ Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS).

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!055

This study presents an experimental investigation conducted on an annular porous metal hydride reactor equipped with radial fins. The reactor was filled with 9 kg of La0.7Ce0.1Ca0.3Ni5, and water was considered as heat transfer fluid. The absorption characteristics were studied under different supply pressures (5–20 bar) and desorption characteristics under different inlet temperatures of heat transfer fluid (30–50 °C). An energy efficiency based on the higher heating value of hydrogen was evaluated for the developed solid-state hydrogen storage device. Further, the effect of pre-sensible heating on desorption performance and energy efficiency was analyzed. Finally, the experimental results were compared with the extensively studied LaNi5 alloy. The results showed that the alloy exhibited a constant desorption rate despite slower desorption kinetics. The energy efficiency of the developed system was found to be 76.76%. The comparison results showed that La0.7Ce0.1Ca0.3Ni5 exhibited higher storage capacity than LaNi5 after 20 cycles and approximately similar absorption and desorption rates. The desorption process without pre-sensible heating was more efficient and reduced overall desorption time by 46.5% than the desorption with pre-sensible heating. However, the desorption process without pre-sensible heating has not significantly affected the energy efficiency. © 2022 Elsevier Ltd

The absorption characteristics were studied under different supply pressures (5–20 bar) and desorption characteristics under different inlet temperatures of heat transfer fluid (30–50 °C). Further, the effect of pre-sensible heating on desorption performance and energy efficiency was analyzed.

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!056

Hydrogen energy is expected to be an “ideal fuel” in the era of decarbonization. The discovery, development, and modification of high-performance hydrogen storage materials are the keys to the future development of solid-state hydrogen storage and hydrogen energy utilization. Magnesium hydride (MgH2), with its high hydrogen storage capacity, abundant natural reserves, and environmental friendliness, has been extensively researched. Herein, we briefly summarize the typical structure and hydrogenation/dehydrogenation reaction mechanism of MgH2 and provide a comprehensive overview of strategies to effectively tune the thermodynamics and kinetics of Mg-based materials, such as alloying, nanosizing, the introduction of additives, and composite modification. With substantial efforts, great achievements have been achieved, such as lower absorption/desorption temperatures and better cycling stability. Nonetheless, some pivotal issues remain to be addressed, such as unfavorable hydrogenation/dehydrogenation factors, harsh conditions, slow kinetics, incomplete dehydrogenation, low hydrogen purity, expensive catalysts, and a lack of valid exploration of mechanisms in the hydrogenation/dehydrogenation process. Lastly, some future development prospects of MgH2 in energy-efficient conversion and storage have been presented, including advanced manufacturing ways, stabilization of nanostructures, the introduction of additives combined with structural modification, and utilization of advanced characterization techniques. © 2022

Magnesium hydride (MgH2), with its high hydrogen storage capacity, abundant natural reserves, and environmental friendliness, has been extensively researched. With substantial efforts, great achievements have been achieved, such as lower absorption/desorption temperatures and better cycling stability.

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!057

Solid-state hydrogen storage in various metal hydrides is among the most promising and clean way of storing energy, however, some problems, such as sluggish kinetics and high dehydrogenation temperature should be dealt with. In the present paper the advances of severe plastic deformation on the hydrogenation performance of metal hydrides will be reviewed. Techniques, like high-pressure torsion, equal-channel angular pressing, cold rolling, fast forging and surface modification have been widely applied to induce lattice defects, nanocrystallization and the formation of abundant grain boundaries in bulk samples and they have the potential to up-scale material production. These plastically deformed materials exhibit not only better H-sorption properties than their undeformed counterparts, but they possess better cycling performance, especially when catalysts are mixed with the host alloy promoting potential future applications. ©2023 The Japan Institute of Metals and Materials.

Solid-state hydrogen storage in various metal hydrides is among the most promising and clean way of storing energy, however, some problems, such as sluggish kinetics and high dehydrogenation temperature should be dealt with. These plastically deformed materials exhibit not only better H-sorption properties than their undeformed counterparts, but they possess better cycling performance, especially when catalysts are mixed with the host alloy promoting potential future applications.

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!058

Sustainable development of hydrogen energy is a prime concern to address the rising energy demand and the global energy problem since the hydrogen economy is reliable for clean and carbon-free energy carriers. Despite well-established commercial sector technologies, boil-off losses, explosive nature, and leakage risk still exist with compressed and liquefied storage. One of the significant remedies, solid-state hydrogen storage, improves bulk density and gravimetric capacity and addresses safety concerns. The rising popularity of light and heavy fuel cell vehicles is projected to promote the advancement of onboard solid-state hydrogen technology. The present review focuses on the importance of existing porous materials, polymers, metal, and complex metal hydrides for solid-state hydrogen storage and the dominance of Si nanostructures (SiNSs). The fabrication techniques of porous silicon, porous silicon nanowires, and Si quantum dots are accentuated. The review provides insights into the hydrogen-assisted properties, regularities, the importance of hydrogen energy on automobiles for alleviating climate change phenomena, and the application of SiNSs for hydrogen storage with other transition and alkali earth materials to overcome the issues. It highlights the importance of catalysts in resolving the existing reversibility and desorption issues associated with hydrogen energy storage. Different popular desorption techniques considering the pore dimensions are discussed. The evaluation may enable energy providers and Si-based fuel cells to be better customized, promoting the development of the hydrogen energy economy. © 2022 Hydrogen Energy Publications LLC

The rising popularity of light and heavy fuel cell vehicles is projected to promote the advancement of onboard solid-state hydrogen technology. Different popular desorption techniques considering the pore dimensions are discussed.

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!059

The lattice distortion effect and cocktail effect of high-entropy oxides (HEOs) will dominate the catalytic effect of the materials, in order to study the influence of the constituent elements of HEOs on the lattice distortion effect and cocktail effect, through elemental manipulation of Cr, Cu, and La, high entropy oxides (HEOs) catalyst CrMnFeCoNiO (Cr1:1), CuMnFeCoNiO (Cu1:1), and LaMnFeCoNiO (La1:1) were effectively synthesized by the facile co-precipitation approach. With a size of about 10 nm, Cr1:1 presented significant modification impacts on enhancing the hydrogen storage capability of MgH2. Specifically, MgH2 was able to release hydrogen at 200 °C with the addition of Cr1:1, MgH2+10wt% Cr1:1 showed prompt rate of dehydrogenation which could release 5.56 wt% H2 in 20 min at 250 °C, and the activation energy of MgH2 was lowered to 69.77± 3.75 kJ⋅mol−1 by adding Cr1:1. According to the Chou model fitting, the exceptional kinetic performance of the composite was attributable to a rate-controlling step changed from low-speed surface penetration to high-speed diffusion. Furthermore, MgH2+10wt% Cr1:1 was capable of absorbing hydrogen at ambient temperature and the composite could uptake 6 wt% H2 within 8 min at the temperature of 150 °C. Due to the high entropy effects of HEOs, Cr1:1 possessed superior stability, which guarantees the robust cycling qualities of MgH2+10wt% Cr1:1. Meanwhile, microstructure analysis revealed that the active sites with numerous heterogeneous structures were uniformly dispersed on surfaces, exhibiting superior catalytic effects on improving the hydrogen storage performance of MgH2. © 2024

Furthermore, MgH2+10wt% Cr1:1 was capable of absorbing hydrogen at ambient temperature and the composite could uptake 6 wt% H2 within 8 min at the temperature of 150 °C. Meanwhile, microstructure analysis revealed that the active sites with numerous heterogeneous structures were uniformly dispersed on surfaces, exhibiting superior catalytic effects on improving the hydrogen storage performance of MgH2.

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!060

The quadrupole coupling constant CQ and the asymmetry parameter η have been determined for two complex aluminium hydrides from 27Al NMR spectra recorded for stationary samples by using the Solomon echo sequence. The thus obtained data for KAlH4 (CQ=(1.30±0.02) MHz, η=(0.64±0.02)) and NaAlH4 (CQ=(3.11±0.02) MHz, η<0.01) agree very well with data previously determined from MAS NMR spectra. The accuracy with which these parameters can be determined from static spectra turned out to be at least as good as via the MAS approach. The experimentally determined parameters (δiso, CQ and η) are compared with those obtained from DFT-GIPAW (density functional theory – gauge-including projected augmented wave) calculations. Except for the quadrupole coupling constant for KAlH4, which is overestimated in the GIPAW calculations by about 30 %, the agreement is excellent. Advantages of the application of the Solomon echo sequence for the measurement of less stable materials or for in situ studies are discussed. © 2023 The Authors. Published by Wiley-VCH GmbH.

The accuracy with which these parameters can be determined from static spectra turned out to be at least as good as via the MAS approach. The experimentally determined parameters (δiso, CQ and η) are compared with those obtained from DFT-GIPAW (density functional theory – gauge-including projected augmented wave) calculations.

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!061

Research on renewable energy and energy storage systems has been quite active as a result of the upcoming global challenge in both the energy and environmental domains. As a kind of clean energy with water as the only post-combustion product, hydrogen energy has been proposed as possible next-generation energy after decades of advancements. Despite advanced technologies have been developed for mass production of hydrogen from water splitting, hydrogen storage has always been an issue. Magnesium-based (Mg-based) solid-state hydrogen storage materials are promising due to their high energy storage densities, and research related to this field has skyrocketed in recent years. This paper discusses advanced research regarding the Mg-based solid-state hydrogen storage material and the new energy automobile market demand. The advantages and disadvantages and hydrogen storage performance of different Mg-based materials were compared, and the methods to improve the hydrogen storage density and hydrogen storage performance of the Mg-based hydrogen storage materials were summarized. It was found that Mg-based alloys are the most promising candidate for further industrial scale production, and the more advanced materials such as the Mg(BH)4 and the MgH2/graphene composites are the materials that need more research. Finally, applying Mg-based hydrogen fuel cells in new energy vehicles is promising. This paper hopes to provide the researchers with a state-of-the-art understanding of the advanced Mg-based hydrogen storage materials and hopefully help facilitate the hydrogen-related economy in the coming decades. © 2023 SPIE.

Magnesium-based (Mg-based) solid-state hydrogen storage materials are promising due to their high energy storage densities, and research related to this field has skyrocketed in recent years. Finally, applying Mg-based hydrogen fuel cells in new energy vehicles is promising.

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!062

High thermal stability and sluggish absorption/desorption kinetics are still important limitations for using magnesium hydride (MgH2) as a solid-state hydrogen storage medium. One of the most effective solutions in improving hydrogen storage properties of MgH2 is to introduce a suitable catalyst. Herein, a novel nanoparticulate ZrNi with 10-60 nm in size was successfully prepared by co-precipitation followed by a molten-salt reduction process. The 7 wt % nano-ZrNi-catalyzed MgH2 composite desorbs 6.1 wt % hydrogen starting from ∼178 °C after activation, lowered by 99 °C relative to the pristine MgH2 (∼277 °C). The dehydrided sample rapidly absorbs ∼5.5 wt % H2 when operating at 150 °C for 8 min. The remarkably improved hydrogen storage properties are reasonably ascribed to the in situ formation of ZrH2, ZrNi2, and Mg2NiH4 caused by the disproportionation reaction of nano-ZrNi during the first de-/hydrogenation cycle. These catalytic active species are uniformly dispersed in the MgH2 matrix, thus creating a multielement, multiphase, and multivalent environment, which not only largely favors the breaking and rebonding of H-H bonds and the transfer of electrons between H- and Mg2+ but also provides multiple hydrogen diffusion channels. These findings are of particularly scientific importance for the design and preparation of highly active catalysts for hydrogen storage in light-metal hydrides. © 2023 American Chemical Society.

High thermal stability and sluggish absorption/desorption kinetics are still important limitations for using magnesium hydride (MgH2) as a solid-state hydrogen storage medium. The dehydrided sample rapidly absorbs ∼5.5 wt % H2 when operating at 150 °C for 8 min.

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!063

Although MgH2 is widely regarded as one of the most promising solid-state hydrogen storage materials, the high operating temperature and sluggish kinetics of hydrogenation and dehydrogenation are major challenges for its practical application. Herein, V6O13 nanobelts with a thickness of 11 nm are fabricated to promote the reversible hydrogen storage performance of MgH2. The favorable interaction between V6O13 nanobelts and MgH2 leads to in situ homogeneous formation of metallic V during the initial dehydrogenation of MgH2. Induced by the catalysis of metallic V, which results in weaker structural stability and higher surface states of MgH2 attributed to the strong bonding interactions between V and H, the energy required for H2 desorption from MgH2 is decreased to 49.5 kJ mol−1, 10.9 kJ mol−1 lower than that of pristine MgH2. Moreover, during the reversible hydrogenation process, the catalysis of metallic V lowers the energy for H2 adsorption and dissociation on Mg down to −5.904 and 0.023 eV, respectively, while those values reach −0.086 and 1.103 eV for pristine Mg. As a result, with the introduction of V6O13 nanobelts with an ultralow content of 3 wt%, a systematic hydrogen storage capacity of 6.8 wt% could be retained at 250 °C after 10 cycles. © 2023 The Royal Society of Chemistry.

Although MgH2 is widely regarded as one of the most promising solid-state hydrogen storage materials, the high operating temperature and sluggish kinetics of hydrogenation and dehydrogenation are major challenges for its practical application. Induced by the catalysis of metallic V, which results in weaker structural stability and higher surface states of MgH2 attributed to the strong bonding interactions between V and H, the energy required for H2 desorption from MgH2 is decreased to 49.5 kJ mol−1, 10.9 kJ mol−1 lower than that of pristine MgH2.

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!064

AB5 type hydrogen storage alloys have been widely used in Ni-MH batteries due to their high electrochemical capacity, excellent rate performance, and low pollution. However, the high activation difficulty limited their development in the solid-state hydrogen storage field. Mechanical alloying to synthesize composites is an effective way to reduce activation energy. In this paper, the structure and hydrogen storage properties of the LaNi5+nAlH3 (n = 0, 1, 3 wt.%) composites were investigated. The results show that with the incremental of AlH3 alloying content, the lattice constant a, b, and c and the volume (V) of the LaNi5 unit cell tend to increase, the hydrogen absorption platform pressure of the composite material gradually decreased, and the hydrogen release platform pressure gradually increased. It resulted in a reduction in the hysteresis factor (Hf) of the composite from 0.66 to 0.35. This will reduce energy waste during energy conversion. In addition, the activation property of the alloy was improved after AlH3 alloying. This will facilitate the application of AB5 type hydrogen storage alloys. © Published under licence by IOP Publishing Ltd.

AB5 type hydrogen storage alloys have been widely used in Ni-MH batteries due to their high electrochemical capacity, excellent rate performance, and low pollution. This will facilitate the application of AB5 type hydrogen storage alloys.

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!065

Lithium alanate (LiAlH4) is one of the most preferred materials for solid-state hydrogen storage materials owing to its relatively high hydrogen capacity (10.5 wt%). However, its high decomposition temperature and sluggish desorption kinetic restrict its potential application as a hydrogen storage medium for on-board hydrogen-powered applications. To overcome these problems, the impacts of Ni0.6Zn0.4O synthesized via a solid-state method on the desorption properties of LiAlH4 have been examined in this study. It was found that after the introduction of 10 wt% of Ni0.6Zn0.4O to LiAlH4, hydrogen started to release at 124 °C and 170 °C for the first two stages, respectively. Isothermal desorption kinetics also revealed that faster desorption kinetics can be observed at 90 °C for 120 min LiAlH4+10 wt% of Ni0.6Zn0.4O can desorb 3.1 wt% of H2, whereas undoped LiAlH4 can release approximately less than 0.5 wt% of H2 in the same time frame. According to the Kissinger method, the apparent activation energies for the first two steps of the LiAlH4+10 wt% of Ni0.6Zn0.4O composites have been found to be 73 kJ/mol and 85 kJ/mol, respectively, 32 kJ/mol and 40 kJ/mol less than milled LiAlH4. The in-situ formation of NiO and Zn or Zn-containing compounds during the heating process might contribute to the kinetic improvement of LiAlH4. © 2023 Hydrogen Energy Publications LLC

To overcome these problems, the impacts of Ni0.6Zn0.4O synthesized via a solid-state method on the desorption properties of LiAlH4 have been examined in this study. It was found that after the introduction of 10 wt% of Ni0.6Zn0.4O to LiAlH4, hydrogen started to release at 124 °C and 170 °C for the first two stages, respectively.

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!066

Magnesium hydride (MgH2) is the mostly used material for solid-state hydrogen storage. However, their slow kinetics and highly unfavorable thermodynamics make them unsuitable for the practical applications. The current study describes the unusual catalytic action of a new class of catalyst, a high-entropy alloy (HEA) of Al20Cr16Mn16Fe16Co16Ni16 and its leached version, on the de/re-hydrogenation properties of MgH2. The onset desorption temperature of MgH2 was reduced significantly from 360 °C (for ball-milled MgH2) to 338 °C when it was catalyzed with a leached HEA-based catalyst. On the other hand, a fast de/re-hydrogenation kinetics of MgH2 was observed during the addition of leached HEA-based catalyst. It absorbed ∼6.1 wt% of hydrogen in just 2 min at a temperature of 300 °C under 10 atm hydrogen pressure and desorbed ∼5.4 wt% within 40 min. At moderate temperatures and low pressure, the HEA-based catalyst reduced desorption temperatures and improved re-hydrogenation kinetics. Even after 25 cycles of de/re-hydrogenation, the storage capacity of MgH2 catalyzed with the leached version of HEA degrades negligibly. © 2023 Hydrogen Energy Publications LLC

Magnesium hydride (MgH2) is the mostly used material for solid-state hydrogen storage. However, their slow kinetics and highly unfavorable thermodynamics make them unsuitable for the practical applications.

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!067

Ammonia borane (AB) has been extensively studied as a solid-state hydrogen storage material. On the other hand, its reactivity with CO2 is still unclear, especially in the solid state. By carefully controlling the CO2 pressure and temperature, AB efficiently reduces a large amount of CO2 without solvent or catalyst. 40 mmol of CO2 reacts with one mole of AB at 0.5 MPa and 60 °C. The mechanism was investigated by NMR and DFT calculation. The reaction proceeds through the formation of diammoniate of diborane (DADB) as an intermediate, followed by the reduction and fixation of CO2 with BH4− to give triformatoborohydride ([HB(OCHO)3]−). Aldehyde is then transferred from B to N, yielding formamide as the main final product. The N-formylation of secondary amine can also be achieved without solvent. Finally, the pyrolysis of the product between AB and CO2 produces N-doped amorphous carbon, opening the door to new clean CO2 valorisation pathways. © 2024 The Royal Society of Chemistry.

By carefully controlling the CO2 pressure and temperature, AB efficiently reduces a large amount of CO2 without solvent or catalyst. Aldehyde is then transferred from B to N, yielding formamide as the main final product.

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!068

Over the last few decades, hydrogen fuel has been considered to be a major alternative source of renewable energy due to increasing environmental pollution and the depletion of nonrenewable energy. The need to efficiently produce and store hydrogen, therefore, has necessitated the development of several technologies and materials for hydrogen storage to achieve the envisaged hydrogen economy. Solid-state hydrogen storage in magnesium hydride (MgH2) has shown a huge potential owing to its impressively high gravimetric and volumetric hydrogen capacities of ca. 7.6 wt% and 111 g/L, respectively. However, the bottleneck to the wide applications of MgH2 as a commercial source of hydrogen fuel is the delivery temperature requirement of ca. 300-400°C due to thermodynamic stability (ca. 76 kJ/mol-H2), and the slow kinetics of hydrogen de/absorption. Nanostructuring and catalysis are marked as the most promising strategies for modifying the properties of MgH2. Doping MgH2 with nanoscale materials can lower the delivery temperature and bring it nearer to commercial applications. Recently, MXenes, a group of 2D nanomaterials composed of transition metal carbides/nitrides/carbonitrides layers, have demonstrated the dual roles of storing hydrogen and enhancing the hydrogen evolution reactions of lightweight metal hydrides especially MgH2. This review article, therefore, provides explicit insights into MXenes, their recent applications as potential materials for storing hydrogen, and as functional additives for enhancing the hydrogen reaction of MgH2 with an outlook. © 2022

Doping MgH2 with nanoscale materials can lower the delivery temperature and bring it nearer to commercial applications. This review article, therefore, provides explicit insights into MXenes, their recent applications as potential materials for storing hydrogen, and as functional additives for enhancing the hydrogen reaction of MgH2 with an outlook.

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!069

Solid-state hydrogen storage materials have been considered as one of the most promising hydrogen storage methods due to the advantages of high volumetric density, flexible transportation, good safety, etc. The development of hydrides with reversible hydrogen capability at low temperature (<80 ℃) is of great significance for expanding the application of solid-state hydrogen storage technology. The low thermodynamic stability of transition metal alanates may meet the low-temperature requirements of hydrogen storage systems, which has the potential values of fundamental research and applications. This paper not only systematically reviews the research progress of transition metal alanates, including the preparation methods, structural and property characterizations, underlying mechanisms, etc., but also discusses the main problems and development trend, which aims to provide reference for the further study of transition metal alanates. © 2023 Materials China. All rights reserved.

Solid-state hydrogen storage materials have been considered as one of the most promising hydrogen storage methods due to the advantages of high volumetric density, flexible transportation, good safety, etc. This paper not only systematically reviews the research progress of transition metal alanates, including the preparation methods, structural and property characterizations, underlying mechanisms, etc., but also discusses the main problems and development trend, which aims to provide reference for the further study of transition metal alanates.

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!070

Hydrogen energy is regarded as the clean energy with the most development potential. In order to realize the large-scale application of hydrogen energy, the problem of hydrogen storage must be solved. At present, there are three main ways of hydrogen storage, namely compressed hydrogen storage, liquid hydrogen storage, and solid-state hydrogen storage. Compressed hydrogen storage is the most commonly used hydrogen storage method. After the hydrogen is compressed, it is stored in the form of gas in a cylinder. It has the advantages of low cost and fast charging and discharging speed, but its volumetric hydrogen storage density is extremely low. Liquid hydrogen storage is a cryogenic hydrogen storage technology. After the hydrogen is compressed, it is cryogenically cooled to below −253°C to become liquid hydrogen for storage. Liquid hydrogen has the advantages of high storage efficiency and good volumetric hydrogen storage density, but the liquefaction of hydrogen requires a lot of energy, so its storage cost is high. Solid-state hydrogen storage technology is one of the most promising hydrogen storage technologies, which utilizes the physical adsorption or chemical reaction characteristics between hydrogen and materials to store hydrogen. It has the advantages of good safety and high volumetric hydrogen storage density. Therefore, solid-state hydrogen storage is considered to be one of the most promising hydrogen storage technologies. However, in order to develop solid-state hydrogen storage technology, we must find and develop high-performance hydrogen storage materials, which have become a top priority. The current chapter mainly presents an overview of the developments of three hydrogen storage technologies. In particular, the solid-state hydrogen storage technology and hydrogen storage alloys are emphatically introduced. © 2024 Elsevier Inc. All rights reserved.

It has the advantages of good safety and high volumetric hydrogen storage density. However, in order to develop solid-state hydrogen storage technology, we must find and develop high-performance hydrogen storage materials, which have become a top priority.

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!071

This work investigates the graphitic carbon nitride (g-C3N4) and g-C3N4/CoMn2O4 nanocomposites as potential materials for solid-state hydrogen storage applications. Initially, the CoMn2O4 was prepared by facile hydrothermal technique and g-C3N4 was synthesized via a one-step calcination process. The g-C3N4/CoMn2O4 composites were prepared through ultrasonic-assisted wet impregnation method and their physical and chemical properties were investigated systematically. Thermogravimetric analysis confirmed that the samples were thermally stable up to 500 °C. Hydrogenation studies were carried out at 150 °C for 30 min under 5 and 10 bar pressures. In the dehydrogenation process, the g-C3N4 desorbed 1.58 wt% and g-C3N4/CoMn2O4 650 nanocomposite desorbed 2.25 wt% of hydrogen from RT to 500 °C. The g-C3N4/CoMn2O4 650 shows lower desorption activation energy and binding energy (Ed = 15.81 kJ mol−1 & Eb = 0.252 eV) compared to g-C3N4 (Ed = 16.54 kJ mol−1 & Eb = 0.260 eV) respectively. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.

This work investigates the graphitic carbon nitride (g-C3N4) and g-C3N4/CoMn2O4 nanocomposites as potential materials for solid-state hydrogen storage applications. Hydrogenation studies were carried out at 150 °C for 30 min under 5 and 10 bar pressures.

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!072

This study emphasizes the catalytic function of TiF3 on hydrogen storage properties and the reaction mechanism of the MgH2-Na3AlH6-LiBH4 produced by employing the ball-milling technique, which has a molar ratio of 1:1:4. It discovered that the mixture of Na3AlH6 and LiBH4 reacted through a metathesis reaction and transformed into Li3AlH6 and NaBH4 composite upon the ball milling procedure. MgH2-Li3AlH6-NaBH4 destabilized system with TiF3 catalyst has displayed four decomposition tiers throughout the heating procedure. The initial tier of hydrogen release in the composite occurs at temperatures of 100 °C and 75 °C lower than in the catalyst-free composite. Continuous heating resulted in two through four dehydrogenation tiers, with an overall capacity of 10.1 wt% hydrogens released (at temperatures of 200 °C, 350 °C, and 400 °C, respectively). In contrast to the Mg-Na-Al-Li-B-H catalyst-free composite, incorporating the TiF3 catalyst demonstrates a faster hydrogen uptake and release rate. The apparent activation energy (Ea) for the dissociation of Li3AlH6, MgH2, and NaBH4 in the composite with TiF3 catalyst was remarkably abridged compared to the catalyst-free ternary system (Kissinger plot; 23, 20, and 13 kJ/mol, respectively for doped composite). TiF3's considerable catalytic performance is ascribed to the in-situ production of Al[sbnd]Ti and Al[sbnd]F phases during the dehydrogenation process of TiF3 and Li3AlH6. Once generated, the Al[sbnd]Ti and Al[sbnd]F phase serves as a genuine catalyst in the MgH2-Na3AlH6-4LiBH4-TiF3 ternary system. © 2023 Elsevier Ltd

MgH2-Li3AlH6-NaBH4 destabilized system with TiF3 catalyst has displayed four decomposition tiers throughout the heating procedure. TiF3's considerable catalytic performance is ascribed to the in-situ production of Al[sbnd]Ti and Al[sbnd]F phases during the dehydrogenation process of TiF3 and Li3AlH6.

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!073

Although Mg-based hydrides are extensively considered as a prospective material for solid-state hydrogen storage and clean energy carriers, their high operating temperature and slow kinetics are the main challenges for practical application. Here, a Mg–Ni based hydride, Mg2NiH4 nanoparticles (∼100 nm), with dual modification strategies of nanosizing and alloying is successfully prepared via a gas-solid preparation process. It is demonstrated that Mg2NiH4 nanoparticles form a unique chain-like structure by oriented stacking and exhibit impressive hydrogen storage performance: it starts to release H2 at ∼170 °C and completes below 230 °C with a saturated capacity of 3.32 wt% and desorbs 3.14 wt% H2 within 1800 s at 200 °C. The systematic characterizations of Mg2NiH4 nanoparticles at different states reveal the dehydrogenation behavior and demonstrate the excellent structural and hydrogen storage stabilities during the de/hydrogenated process. This research is believed to provide new insights for optimizing the kinetic performance of metal hydrides and novel perspectives for designing highly active and stable hydrogen storage alloys. © 2023 The Authors

Although Mg-based hydrides are extensively considered as a prospective material for solid-state hydrogen storage and clean energy carriers, their high operating temperature and slow kinetics are the main challenges for practical application. This research is believed to provide new insights for optimizing the kinetic performance of metal hydrides and novel perspectives for designing highly active and stable hydrogen storage alloys.

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!074

For solid-state hydrogen storage, Mg(BH4)2 has long been recognized as a promising material. However, its higher thermal stability is distant from conditions for practical application. Herein, it is effectively established that VF4 nanoparticles anchored on 2D Mxene Ti3C2 (VF4@Ti3C2) have efficiently catalytic effects towards the hydrogen storage process of Mg(BH4)2. The MBH-VF4@Ti3C2 sample started releasing hydrogen at 90 °C, which was 182 °C and 55 °C lower than those of additive-free Mg(BH4)2 and MBH-20Ti3C2 composites. Additionally, the MBH-20VF4@Ti3C2 composite desorbed more than 8 wt% H2 at 275 °C. The activation energies of dehydrogenation were reduced, and the improved reversibility of VF4@Ti3C2-doped Mg(BH4)2 was also discussed. According to microstructural study, the heterostructural VF4@Ti3C2 interacted with Mg(BH4)2 to produce VH2.01 and metallic Ti during re/dehydrogenation, which worked as active species to improve hydrogen storage performance in Mg(BH4)2. © 2023 Elsevier B.V.

For solid-state hydrogen storage, Mg(BH4)2 has long been recognized as a promising material. Herein, it is effectively established that VF4 nanoparticles anchored on 2D Mxene Ti3C2 (VF4@Ti3C2) have efficiently catalytic effects towards the hydrogen storage process of Mg(BH4)2.

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!075

As an ideal material for solid-state hydrogen storage, magnesium hydride (MgH2) has attracted enormous attention due to its cost-effectiveness, abundant resources, and outstanding reversibility. However, the high thermodynamics and poor kinetics of MgH2 still hinder its practical application. In this work, a simple stirring-hydrothermal method was used to successfully prepare bimetallic Mn3O4/ZrO2 nanoparticles, which were subsequently doped into MgH2 by mechanical ball milling to improve its hydrogen sorption performance. The MgH2 + 10 wt% Mn3O4/ZrO2 composite began discharging hydrogen at 219 °C, which was 111 °C lower compared to the as-synthesized MgH2. At 250 °C, the MgH2 + 10 wt% Mn3O4/ZrO2 composite released 6.4 wt% hydrogen within 10 min, whereas the as-synthesized MgH2 reluctantly released 1.4 wt% hydrogen even at 335 °C. Moreover, the dehydrogenated MgH2 + 10 wt% Mn3O4/ZrO2 sample started to charge hydrogen at room temperature. 6.0 wt% hydrogen was absorbed when heated to 250 °C under 3 MPa H2 pressure, and 4.1 wt% hydrogen was taken up within 30 min at 100 °C at the same hydrogen pressure. In addition, compared with the as-synthesized MgH2, the de/rehydrogenation activation energy values of the MgH2 + 10 wt% Mn3O4/ZrO2 composite were decreased to 64.52 ± 13.14 kJ mol−1 and 16.79 ± 4.57 kJ mol−1, respectively, which incredibly contributed to the enhanced hydrogen de/absorption properties of MgH2 © 2023 The Royal Society of Chemistry.

As an ideal material for solid-state hydrogen storage, magnesium hydride (MgH2) has attracted enormous attention due to its cost-effectiveness, abundant resources, and outstanding reversibility. However, the high thermodynamics and poor kinetics of MgH2 still hinder its practical application.

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!076

Vanadium-based alloys are considered to be one of the most promising hydrogen storage materials due to their high hydrogen storage capacity under ambient conditions. However, their complex activation at high temperature and poor stability pose serious challenges for large-scale applications. In this work, a series of TiCr3V16Cex (x = 0, 0.1, 0.2, 0.4, 1) hydrogen storage alloys were developed with different Ce contents using arc melting. The hydrogen storage and desorption performance, activation mechanism, and hydrogen absorption mechanism of the prepared alloys were investigated. Physical characterization confirms that the alloy is body-centered cubic (BCC) with Ce dopants, which exist in the form of oxides. The pressure-composition-temperature (PCT) test showed that the hydrogen storage plateau pressure of the Ce-doped alloy is increased compared to the Ce-free counterparts, while the hydrogen storage capacity decreased slightly with increasing Ce content. In addition, the influence of Ce doping on the alloy kinetics and thermodynamics is also discussed. The results showed that the TiCr3V16Cex (x = 0.2, 0.4, 1) alloys could absorb and release hydrogen at room temperature without activation. As an optimum, the TiCr3V16Ce0.2 alloy shows a hydrogen absorption rate of up to 3.69 wt%, and an effective hydrogen desorption capacity of 2.29 wt% at 25 °C. After hydrogen absorption and desorption cycles, the alloy almost maintains its original capacity. The Ce-doped BCC alloy developed in this work provides a new route to achieve high hydrogen storage performance under mild conditions. © 2022 Elsevier B.V.

In this work, a series of TiCr3V16Cex (x = 0, 0.1, 0.2, 0.4, 1) hydrogen storage alloys were developed with different Ce contents using arc melting. The Ce-doped BCC alloy developed in this work provides a new route to achieve high hydrogen storage performance under mild conditions.

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!077

Hydrogen-based economy has a great potential for addressing the world's environmental concerns by using hydrogen as its future energy carrier. Hydrogen can be stored in gaseous, liquid and solid-state form, but among all solid-state hydrogen storage materials (metal hydrides) have the highest energy density. However, hydrogen accessibility is a challenging step in metal hydride-based materials. To improve the hydrogen storage kinetics, effects of functionalized catalysts/dopants on metal atoms have been extensively studied. The nanostructuring of metal hydrides is a new focus and has enhanced hydrogen storage properties by allowing higher surface area and thus reversibility, hydrogen storage density, faster and tunable kinetics, lower absorption and desorption temperatures, and durability. The effect of incorporating nanoparticles of carbon-based materials (graphene, C60, carbon nanotubes (CNTs), carbon black, and carbon aerogel) showed improved hydrogen storage characteristics of metal hydrides. In this critical review, the effects of various carbon-based materials, catalysts, and dopants are summarized in terms of hydrogen-storage capacity and kinetics. This review also highlights the effects of carbon nanomaterials on metal hydrides along with advanced synthesis routes, and analysis techniques to explore the effects of encapsulated metal hydrides and carbon particles. In addition, effects of carbon composites in polymeric composites for improved hydrogen storage properties in solid-state forms, and new characterization techniques are also discussed. As is known, the nanomaterials have extremely higher surface area (100–1000 time more surface area in m2/g) when compared to the bulk scale materials; thus, hydrogen absorption and desorption can be tuned in nanoscale structures for various industrial applications. The nanoscale tailoring of metal hydrides with carbon materials is a promising strategy for the next generation of solid-state hydrogen storage systems for different industries. © 2023 Hydrogen Energy Publications LLC

Hydrogen-based economy has a great potential for addressing the world's environmental concerns by using hydrogen as its future energy carrier. To improve the hydrogen storage kinetics, effects of functionalized catalysts/dopants on metal atoms have been extensively studied.

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!078

Solid-state hydrogen storage is the best choice for balancing economy and safety among various hydrogen storage technologies, and hydrogen storage in the secondary phase might be a promising solid-state hydrogen storage scheme. In the current study, to unmask its physical mechanisms and details, a thermodynamically consistent phase-field framework is built for the first time to model hydrogen trapping, enrichment, and storage in the secondary phases of alloys. The hydrogen trapping processes, together with hydrogen charging, are numerically simulated using the implicit iterative algorithm of the self-defined finite elements. Some important results are attained: 1. Hydrogen can overcome the energy barrier under the assistance of the local elastic driving force and then spontaneously enter the trap site from the lattice site. The high binding energy makes it difficult for the trapped hydrogens to escape. 2. The secondary phase geometry stress concentration significantly induces the hydrogen to overcome the energy barrier. 3. The manipulation of the geometry, volume fraction, dimension, and type of the secondary phases is capable of dictating the tradeoff between the hydrogen storage capacity and the hydrogen charging rate. The new hydrogen storage scheme, together with the material design ideology, promises a viable path toward the optimization of critical hydrogen storage and transport for the hydrogen economy. © 2023 by the authors.

Solid-state hydrogen storage is the best choice for balancing economy and safety among various hydrogen storage technologies, and hydrogen storage in the secondary phase might be a promising solid-state hydrogen storage scheme. In the current study, to unmask its physical mechanisms and details, a thermodynamically consistent phase-field framework is built for the first time to model hydrogen trapping, enrichment, and storage in the secondary phases of alloys.

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!079

The ability of high-entropy alloys (HEAs) for hydrogen storage is a rather new topic in the hydrogen community. HEAs with the C14 Laves phase have shown a high potential to reversibly store hydrogen at room temperature, but most of these alloys require a high-temperature activation treatment. This study explores the role of interphase boundaries on the easy activation of HEAs at room temperature. Two chemically similar HEAs with single and dual phases, TiV1.5ZrCr0.5MnFeNi (C14 + 4 vol% BCC phases) and TiV1.5Zr1.5CrMnFeNi (single C14 phase), are designed and synthesized. While the dual-phase alloy readily absorbs hydrogen at room temperature without any activation treatment, the single-phase alloy requires a high-temperature activation. It is suggested that interphase boundaries not only provide pathways for easy hydrogen transport and activation of HEAs at room temperature but also act as active sites for heterogeneous nucleation of hydride. This study introduces interphase-boundary generation as an effective strategy to address the activation drawback of HEAs. © 2023 Hydrogen Energy Publications LLC

It is suggested that interphase boundaries not only provide pathways for easy hydrogen transport and activation of HEAs at room temperature but also act as active sites for heterogeneous nucleation of hydride. This study introduces interphase-boundary generation as an effective strategy to address the activation drawback of HEAs.

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!080

Solid-state hydrogen storage is crucial for the widespread applications of hydrogen energy. It is a grand challenge to find appropriate materials that provide high hydrogen density and ambient temperature stability. Herein, we investigated the potential of Ti-decorated Irida-Graphene, a promising effective hydrogen storage system, as a novel hydrogen storage material using first-principles calculation. Irida-Graphene is a two-dimensional isomer of carbon consisting of tri-, hexa-, and octagon rings of carbon. Ti atoms are tightly bounded to the hexagonal rings. Binding energy analysis reveals that a single Ti atom in the primitive unit-cell of Ti-decorated Irida-Graphene is capable to bind up with 5H2 molecules and the average adsorption energy was −0.41 eV/H2. It indicates the gravimetric density of 7.7 wt%. The stability is attributed to Kubas-type interactions and ensured by a 5.0 eV diffusion energy barrier that prevents the Ti–Ti clustering. Further, ab initio molecular dynamics simulations results illustrate that the system remains stable at 600 K, higher than the desorption temperature of 524 K, implying the stability of the system during hydrogen recharge and discharge. The exceptional hydrogen storage performance suggests that Ti-decorated Irida-Graphene is an outstanding candidate for hydrogen storage materials. © 2023 Hydrogen Energy Publications LLC

It is a grand challenge to find appropriate materials that provide high hydrogen density and ambient temperature stability. Binding energy analysis reveals that a single Ti atom in the primitive unit-cell of Ti-decorated Irida-Graphene is capable to bind up with 5H2 molecules and the average adsorption energy was −0.41 eV/H2.

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!081

The catalytic effect of FeCoNiCrMo high entropy alloy nanosheets on the hydrogen storage performance of magnesium hydride (MgH2) was investigated for the first time in this paper. Experimental results demonstrated that 9wt% FeCoNiCrMo doped MgH2 started to de-hydrogenate at 200°C and discharged up to 5.89wt% hydrogen within 60 min at 325°C. The fully dehydrogenated composite could absorb 3.23wt% hydrogen in 50 min at a temperature as low as 100°C. The calculated de/hydrogenation activation energy values decreased by 44.21%/55.22% compared with MgH2, respectively. Moreover, the composite’s hydrogen capacity dropped only 0.28wt% after 20 cycles, demonstrating remarkable cycling stability. The microstructure analysis verified that the five elements, Fe, Co, Ni, Cr, and Mo, remained stable in the form of high entropy alloy during the cycling process, and synergistically serving as a catalytic union to boost the de/hydrogenation reactions of MgH2. Besides, the FeCoNiCrMo nanosheets had close contact with MgH2, providing numerous non-homogeneous activation sites and diffusion channels for the rapid transfer of hydrogen, thus obtaining a superior catalytic effect. © 2023, University of Science and Technology Beijing.

Moreover, the composite’s hydrogen capacity dropped only 0.28wt% after 20 cycles, demonstrating remarkable cycling stability. Besides, the FeCoNiCrMo nanosheets had close contact with MgH2, providing numerous non-homogeneous activation sites and diffusion channels for the rapid transfer of hydrogen, thus obtaining a superior catalytic effect.

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!082

Hydrogen-based energy systems offer potential solutions for replacing fossil fuels in the future. However, the practical utilization of hydrogen energy depends partly on safe and efficient hydrogen storage techniques. The development of hydrogen storage materials has attracted extensive interest for decades. Solid-state hydrogen storage systems based on metal hydride materials provide great promises for many applications. Recently, interest has been revived in TiFe alloys as a prime candidate for stationary hydrogen storage material. The advantages of TiFe alloys over some of the other solid metal hydrides include that it can hydrogenate and dehydrogenate at near room temperature under near atmospheric pressures and that it is a low-cost material because there are abundant supplies of Fe and Ti on the earth's crust. However, the TiFe alloy must be activated at relatively high temperatures (400–450 °C) and high pressure of hydrogen (65 bar) before it can be hydrogenated, which is a hindrance to the industrial-scale application of TiFe alloys. The materials science community on hydrogen storage materials has conducted and reported considerable amounts of studies on TiFe-based alloys. In this work, we provided a comprehensive review of TiFe-based alloys. The fundamentals and synthesis approaches of TiFe-based alloys were summarized. The activation properties of TiFe-based alloys including the understanding of the activation mechanisms and the methods for improving the activation kinetics were reviewed. Moreover, the cycle stability and anti-poisoning ability were discussed. Finally, the potential applications and the perspective of TiFe-based alloys were introduced. © 2023 Elsevier Ltd

Solid-state hydrogen storage systems based on metal hydride materials provide great promises for many applications. Recently, interest has been revived in TiFe alloys as a prime candidate for stationary hydrogen storage material.

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!083

Solid-state hydrogen storage has emerged as an efficient and reliable technique to commercialize hydrogen energy on a large scale. Magnesium hydride (MgH2), amongst other materials, shows excellent hydrogen storage capability. However, it suffers from setbacks like sluggish kinetics and high thermodynamic stability. Several studies have shown that doping with suitable materials is an effective method to improve the sorption kinetics. Current work is concerned with doping of MgH2 with perovskite-type ternary metal oxide NaNbO3 at 5,10 & 15 wt% doping concentration via ball milling and study of its sorption properties. Thermal desorption mass spectra (TDMS) with thermogravimetry (TG) and Differential scanning calorimetry (DSC) validate the optimum doping concentration to be 10 wt% NaNbO3 in MgH2. According to the isothermal hydrogenation plots, 10 wt% catalyzed sample was capable of absorbing 5.29 wt% hydrogen in just 4.2 min at 150ºC which by far outperforms the 2 h milled MgH2 sample which under the same set of conditions absorbs only 0.67 wt% H2. The catalyst starts affecting the absorption rate right from the room temperature whereas the milled sample has minimal absorption throughout the experiment. At room temperature, the average rate of absorption grows by factor 7 which is staggeringly high. The Kissinger analysis reveals activation energy for hydrogen release as 73.12 kJ/mol for 10 wt% doped NaNbO3-MgH2 system while 137.13 kJ/mol for as milled MgH2. The pressure-temperature isotherm (PCI) at four different temperatures gives a quantitative measure of the thermodynamic stability of the system. To fully comprehend the catalytic process, XRD, SEM, and XPS analysis were conducted after each stage of experiment. XPS suggested possible reduction of Nb valance state from + 5 to + 2 due to surface reduction reaction which further accelerated the sorption kinetics due to the electron transfer process. © 2023 Elsevier B.V.

Thermal desorption mass spectra (TDMS) with thermogravimetry (TG) and Differential scanning calorimetry (DSC) validate the optimum doping concentration to be 10 wt% NaNbO3 in MgH2. To fully comprehend the catalytic process, XRD, SEM, and XPS analysis were conducted after each stage of experiment.

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!084

Solid-state hydrogen storage device using metal hydride have enormous advantages for fuel cell forklifts. In addition to high volume hydrogen storage density, the solid-state hydrogen storage device can also be used as a counterweight for the forklift. At the same time, the solid-state storage device has low hydrogen storage pressure and safety, and the fuel (H2) refueling is convenient and low-cost. In this paper, a two-dimensional heat and mass transfer numerical model has been developed to predicting the performance of the metal hydride tank filled with Ti0.9Zr0.1Cr0.35Mn1.4V0.2Fe0.05 alloy. The validity of this numerical model was tested by comparison with the experimental data of the metal hydride hydrogen storage tank with a hydrogen capacity of 1 kg, achieving a good agreement between all the data. And a solid-state hydrogen storage device with an effective hydrogen capacity of 1.5 kg is optimally designed for 3.5 T fuel cell forklift. The completion rate of hydrogen refueling in the solid-state hydrogen storage device will reach 97.6 % within 30 min, and continuously discharging over 1.5 kg H2 under flow rates of 150 SL/min and 250 SL/min. The optimized solid-state hydrogen storage device was integrated in a power module for 3.5 T fuel cell forklift which allows uninterrupted operation for at least 6 h 8 min under rated operation. © 2023

Solid-state hydrogen storage device using metal hydride have enormous advantages for fuel cell forklifts. The optimized solid-state hydrogen storage device was integrated in a power module for 3.5 T fuel cell forklift which allows uninterrupted operation for at least 6 h 8 min under rated operation.

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!085

As a high-density solid-state hydrogen storage material, magnesium hydride (MgH2) is promising for hydrogen transportation and storage. Yet, its stable thermodynamics and sluggish kinetics are unfavorable for that required for commercial application. Herein, nickel/vanadium trioxide (Ni/V2O3) nanoparticles with heterostructures were successfully prepared via hydrogenating the NiV-based two-dimensional layered double hydroxide (NiV-LDH). MgH2 + 7 wt% Ni/V2O3 presented more superior hydrogen absorption and desorption performances than pure MgH2 and MgH2 + 7 wt% NiV-LDH. The initial discharging temperature of MgH2 was significantly reduced to 190 °C after adding 7 wt% Ni/V2O3, which was 22 and 128 °C lower than that of 7 wt% NiV-LDH modified MgH2 and additive-free MgH2, respectively. The completely dehydrogenated MgH2 + 7 wt% Ni/V2O3 charged 5.25 wt% H2 in 20 min at 125 °C, while the hydrogen absorption capacity of pure MgH2 only amounted to 4.82 wt% H2 at a higher temperature of 200 °C for a longer time of 60 min. Moreover, compared with MgH2 + 7 wt% NiV-LDH, MgH2 + 7 wt% Ni/V2O3 shows better cycling performance. The microstructure analysis indicated the heterostructural Ni/V2O3 nanoparticles were uniformly distributed. Mg2Ni/Mg2NiH4 and metallic V were formed in-situ during cycling, which synergistically tuned the hydrogen storage process in MgH2. Our work presents a facile interfacial engineering method to enhance the catalytic activity by constructing a heterostructure, which may provide the mentality of designing efficient catalysts for hydrogen storage. © 2022 Hydrogen Energy Publications LLC

Herein, nickel/vanadium trioxide (Ni/V2O3) nanoparticles with heterostructures were successfully prepared via hydrogenating the NiV-based two-dimensional layered double hydroxide (NiV-LDH). Mg2Ni/Mg2NiH4 and metallic V were formed in-situ during cycling, which synergistically tuned the hydrogen storage process in MgH2.

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!086

Hydrogen storage plays a pivotal role in the hydrogen industry, yet its current status presents a bottleneck. Diverse strategies have emerged in recent years to address this challenge. MgH2 has stood out as a promising solid-state hydrogen storage material due to its impressive gravimetric and volumetric hydrogen density, but its practical application is hampered by elevated thermal stability and sluggish kinetics. In this study, we introduce a solution by synthesizing Pd metallene through a one-pot solvothermal method, revealing a distinctive highly curved lamellar structure with a thickness of around 1.6 nm. Incorporating this Pd metallene into MgH2 results in a composite system wherein the starting dehydrogenation temperature is significantly lowered to 439 K and complete dehydrogenation occurs at 583 K, releasing 6.14 wt.% hydrogen. The activation energy of dehydrogenation for MgH2 was reduced from 170.4 kJ mol–1 to 79.85 kJ mol–1 after Pd metallene decoration. The enthalpy of dehydrogenation of the MgH2–10 wt.% Pd sample was calculated to be 73 kJ mol–1 H2 –1 and decreased by 4.4 kJ mol–1 H2 –1 from that of dehydrogenation of pure MgH2 (77.4 kJ mol–1 H2 –1). Theoretical calculations show that the average formation energy and average adsorption energy of hydrogen vacancies can be significantly reduced in the presence of both Pd clusters and Pd single atoms on the surface of MgH2/Mg, respectively. It suggests that the synergistic effect of in situ formed Pd single atoms and clusters significantly improves the hydrogenation and dehydrogenation kinetics. The identified active sites in this study hold potential as references for forthcoming multi-sized active site catalysts, underscoring a significant advancement toward resolving hydrogen storage limitations. © 2024

MgH2 has stood out as a promising solid-state hydrogen storage material due to its impressive gravimetric and volumetric hydrogen density, but its practical application is hampered by elevated thermal stability and sluggish kinetics. Incorporating this Pd metallene into MgH2 results in a composite system wherein the starting dehydrogenation temperature is significantly lowered to 439 K and complete dehydrogenation occurs at 583 K, releasing 6.14 wt.% hydrogen.

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!087

Magnesium hydride (MgH2) is the most feasible and effective solid-state hydrogen storage material, which has excellent reversibility but initiates decomposing at high temperatures and has slow kinetics performance. Here, zinc titanate (Zn2TiO4) synthesised by the solid-state method was used as an additive to lower the initial temperature for dehydrogenation and enhance the re/dehydrogenation behaviour of MgH2. With the presence of Zn2TiO4, the starting temperature for the dehydrogenation of MgH2 was remarkably lowered to around 290 °C–305 °C. In addition, within 300 s, the MgH2–Zn2TiO4 sample absorbed 5.0 wt.% of H2 and 2.2–3.6 wt.% H2 was liberated from the composite sample in 30 min, which is faster by 22–36 times than as-milled MgH2. The activation energy of the MgH2 for the dehydrogenation process was also downshifted to 105.5 kJ/mol with the addition of Zn2TiO4 indicating a decrease of 22% than as-milled MgH2. The superior behaviour of MgH2 was due to the formation of MgZn2, MgO and MgTiO3, which are responsible for ameliorating the re/dehydrogenation behaviour of MgH2. These findings provide a new understanding of the hydrogen storage behaviour of the catalysed-MgH2 system. © 2023

Magnesium hydride (MgH2) is the most feasible and effective solid-state hydrogen storage material, which has excellent reversibility but initiates decomposing at high temperatures and has slow kinetics performance. In addition, within 300 s, the MgH2–Zn2TiO4 sample absorbed 5.0 wt.% of H2 and 2.2–3.6 wt.% H2 was liberated from the composite sample in 30 min, which is faster by 22–36 times than as-milled MgH2.

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!088

The process of heat-driven mass transfer involved in hydrogen storage within metal hydrides (MHs) demands implementing a heat transfer system (HTS) to facilitate faster hydrogen charging and discharging. One effective method to enhance heat transfer is utilizing an HTS equipped with fins and a cooling tube. Among the crucial factors for optimizing the reactor, fin efficiency (FE) plays a vital role, although it has not been explored in unsteady processes like the present one. This study introduces a novel FE technique to optimize fins in a conventional longitudinal finned tube MH reactor based on LaNi5. Due to the intricacies of the problem, making analytical estimation of FE challenging, the authors turned to the concept of reverse engineering. This approach utilizes simulated data's temporal temperature profiles to calculate the FE. The number of fins is varied from 4 to 12 while keeping the total fin weight constant. Heat transfer performance improved as the number of fins increased, but the FE deteriorated from 0.89 to 0.56 due to the reduction in fin thickness. A performance index (PI) that considers the number of fins is introduced to assess the overall performance. Its values are 0.58, 0.79, 0.96, 1.05, and 1.1 for configurations with 4, 6, 8, 10, and 12 fins, respectively. The configuration with 8 fins is deemed optimal because further increasing the number of fins led to only marginal improvements in PI value. Subsequent optimization of fin shape, precisely radial tapering, had a minimal impact on heat transfer performance. Finally, the desorption behavior was examined for the optimal configuration with 8 fins of constant thickness. © 2023 Elsevier Ltd

One effective method to enhance heat transfer is utilizing an HTS equipped with fins and a cooling tube. Subsequent optimization of fin shape, precisely radial tapering, had a minimal impact on heat transfer performance.

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!089

Magnesium hydride (MgH2) has been under spot light recently when it comes to solid-state hydrogen storage media owing to its superior hydrogen storage capacity, reasonably good reversibility, and cost-effectiveness. Albeit these advantageous attributes, it suffers from the setback of having undesirably high thermodynamic stability and exceedingly sluggish kinetics, which diminishes its feasibility for practical use. The purview of this review article is to first introduce the basic understandings related to sorption kinetic of hydrogen storage material with a emphasis on MgH2 and to elucidate the key developments in the field of exploiting various kinds of Metal Oxide-based catalysts in improving the hydrogenation kinetics of MgH2. The article initiates with brief but sufficiently explanatory discussions on the rudiments of hydrogen sorption in MgH2 followed by an elaborate exposition on the usage of catalyst as a possible means to alleviate some of the shortcomings of the virgin compound. This article assesses a number of factors affecting the catalytic efficiency, e.g., defect density, valance state of the metal ion, oxygen vacancy, etc., which dictates the metal oxide-based catalysts as a prime candidate in this regard. A whole host of binary and ternary metal oxides have been taken under consideration to build up a coherent description of the reaction mechanism, reduction in the activation energy barrier, enhanced sorption rate, and other relevant parameters governing the kinetics of the reaction. The synergistic effect of two or more metal oxide-based catalysts has also been alluded to as this amalgamation of several catalysts has brought to bear a greater degree of enhancement compared to an individual application. This review concludes by delineating a scheme of plausible future modifications that can possibly augment the entire business of hydrogen sorption in Magnesium Hydride. At the end it is suggested that a complete understanding of reaction mechanism for kinetic enhanment is essential before developing more catalysts. A clear understanding will evolute a perfect catalyst that can be realized in practical utility. © 2023 Hydrogen Energy Publications LLC

Magnesium hydride (MgH2) has been under spot light recently when it comes to solid-state hydrogen storage media owing to its superior hydrogen storage capacity, reasonably good reversibility, and cost-effectiveness. Albeit these advantageous attributes, it suffers from the setback of having undesirably high thermodynamic stability and exceedingly sluggish kinetics, which diminishes its feasibility for practical use.

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!090

To explore more possibilities for hydrogen economy, Mg-based alloys containing long period stacking ordered (LPSO) phase for solid-state hydrogen storage deserve attention. In this paper, indium (In) element is adopted to alter the de/hydrogenation abilities of Mg–Y–Zn alloys. The relationship between microstructural features and hydrogen storage behaviors of Mg95Y3Zn2-xInx (x = 0, 1 and 2 at.%) alloys are discussed in detail. Indium element can modify the morphology of LPSO phase and more Mg interfaces are obtained. LPSO phase cannot be generated when Zn is completely replaced by In element; instead α-Mg grains and eutectic phase (Mg + MgYIn) the constitute the In2 alloy. Element In benefits the activation process of the alloys in this paper, which helps the alloy particles to be hydrogenated quickly in the first hydrogenation. Specifically, 1 at.% In substitution for Zn accelerates dehydrogenation and the dehydrogenation temperature reduces by 11 °C. The benefits of In element for dehydrogenation behaviors mainly come from increased Mg grain boundaries, larger MgH2 lattice constants with weaker Mg–H bonds, uniformly distributed nanoscale YH2/YH3 phase. © 2023 Hydrogen Energy Publications LLC

Indium element can modify the morphology of LPSO phase and more Mg interfaces are obtained. The benefits of In element for dehydrogenation behaviors mainly come from increased Mg grain boundaries, larger MgH2 lattice constants with weaker Mg–H bonds, uniformly distributed nanoscale YH2/YH3 phase.

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!091

Laves phase high-entropy alloys are considered as good candidates for hydrogen storage applications. However, they usually suffer from poor first hydrogenation kinetics, the so-called activation process. In this paper, we attempt to solve the activation problem of the Ti0.5Zr0.5(Mn1-xFex)Cr1 (x = 0, 0.2 and 0.4) by high-pressure torsion (HPT). The HPT process was carried out under 6 GPa pressure for 5 revolutions in air on samples synthesized by arc melting. The hydrogenation kinetics were measured using a Sievert's type apparatus at room temperature under 2 MPa of hydrogen pressure. While the as-cast alloys become totally inert to hydrogen after air exposure, the HPT-processed samples absorb 1.6–1.8 wt% of hydrogen at room temperature in a few seconds even after air exposure for 2 months. The easy activation of alloys processed by HPT is due to the formation of lattice defects that act as nucleation points. These results confirm that HPT processing is an effective strategy to develop active hydrogen storage materials. © 2023 Elsevier B.V.

The HPT process was carried out under 6 GPa pressure for 5 revolutions in air on samples synthesized by arc melting. The hydrogenation kinetics were measured using a Sievert's type apparatus at room temperature under 2 MPa of hydrogen pressure.

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!092

The low-cost production, safe storage and transportation, and efficient application of hydrogen are the focus of the current hydrogen energy researches. Among them, safe and efficient storage and transportation is the technical key to the large-scale application of hydrogen energy, so the research and development of high-capacity solid hydrogen storage materials have both academic significance and application value. Hydrogen storage by solid material has become the most promising hydrogen storage technology due to its large storage density and high safety factor, which has received widespread attention from researchers. In this paper, according to the current research status of solid hydrogen storage materials, the research progress of several solid hydrogen storage materials is discussed, including those based on physical adsorption, metal, coordinated hydride and hydrate. The most promising magnesium-based hydrogen storage materials are re-evaluated, and the effects of several modification methods such as alloying, nano-anodization, adding catalysts, and composite light metal coordination hydrides on the hydrogen storage mechanism, microstructure, thermodynamic properties and kinetic properties of magnesium-based hydrogen storage materials are elaborated. The integrated design considering production, storage and use of hydrogen should be the development trend for the industrialization of solid hydrogen storage. © 2023 Chemical Industry Press. All rights reserved.

In this paper, according to the current research status of solid hydrogen storage materials, the research progress of several solid hydrogen storage materials is discussed, including those based on physical adsorption, metal, coordinated hydride and hydrate. The most promising magnesium-based hydrogen storage materials are re-evaluated, and the effects of several modification methods such as alloying, nano-anodization, adding catalysts, and composite light metal coordination hydrides on the hydrogen storage mechanism, microstructure, thermodynamic properties and kinetic properties of magnesium-based hydrogen storage materials are elaborated.

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!093

Hydrogen energy is a key role in novel renewable energy production/consumption technologies. Traditional hydrogen energy systems are suffered from low density, high production cost, low efficiency, and storage complications. With the start of solid-state hydrogen storage technology, many of above deficiencies are fulfilled, however, there are several unknown points, particularly in metal oxides, which need more attention. Hydrogen sorption on the layered materials or inside porous materials is a hopeful key to drawbacks for high-performance hydrogen sorption. Hereupon, layered solids with the merit of hydrogen sorption are introduced, for the first time, including “nanostructured bi-metal oxide (BMO)” and “graphitic carbon nitride (CN)”. Perovskites are ceramic and they are hard materials so they could be a favorable candidate for solid-state hydrogen storage. g-C3N4 has attractive features including high surface area, chemical stability, small band gap, and low-cost synthesis methods but also has great potential as an electrode material for energy storage capacitors. The main motivation for this study comes from the potential applications for perovskite materials and graphitic carbon nitride for the solid-state hydrogen storage method. The Perovskite type GdFeO3 nanostructures (as BMO) synthesized through sol-gel approach in front of natural source of Grape juice as both complexing agent and fuel. The experimental scrutinization ascertains an original fabrication of GdFeO3 (GF) nanostructures in Grape juice at 800 °C, with an approximately uniform nanosized structure of 70 nm on average. The obtained pure GF nanostructures are then utilized for nanocomposite formation based on g-C3N4 (CN) with different amounts. The resulting nanocomposites with the ratio of 1:2 from GF:CN perform a preferable hydrogen sorption capacity, in terms of “maximum discharge capacity of 577 mAhg−1” in 2 M KOH electrolyte. It should be declared that however, the discharge capacity of the nanostructured GF is 188 mAhg−1. It can be emphasized that these GF/CN nanocomposites can be utilized as hopeful hosts in an electrochemical hydrogen storage setup due to the synergic effect of g-C3N4 with essential characteristics in cooperation with BMO nanostructures as acceptable electrocatalysts. © 2022 Hydrogen Energy Publications LLC

The obtained pure GF nanostructures are then utilized for nanocomposite formation based on g-C3N4 (CN) with different amounts. It can be emphasized that these GF/CN nanocomposites can be utilized as hopeful hosts in an electrochemical hydrogen storage setup due to the synergic effect of g-C3N4 with essential characteristics in cooperation with BMO nanostructures as acceptable electrocatalysts.

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!094

We develop a continuum framework applicable to solid-state hydrogen storage, cell biology and other scenarios where the diffusion of a single constituent within a bulk region is coupled via adsorption/desorption to reactions and diffusion on the boundary of the region. We formulate content balances for all relevant constituents and develop thermodynamically consistent constitutive equations. The latter encompass two classes of kinetics for adsorption/desorption and chemical reactions - fast and Marcelin-De Donder, and the second class includes mass action kinetics as a special case. We apply the framework to derive a system consisting of the standard diffusion equation in bulk and FitzHugh-Nagumo type surface reaction-diffusion system of equations on the boundary. We also study the linear stability of a homogeneous steady state in a spherical region and establish sufficient conditions for the occurrence of instabilities driven by surface diffusion. These findings are verified through numerical simulations which reveal that instabilities driven by diffusion lead to the emergence of steady-state spatial patterns from random initial conditions and that bulk diffusion can suppress spatial patterns, in which case temporal oscillations can ensue. We include an extension of our framework that accounts for mechanochemical coupling when the bulk region is occupied by a deformable solid. This article is part of the theme issue 'Foundational issues, analysis and geometry in continuum mechanics'. © 2023 The Authors.

These findings are verified through numerical simulations which reveal that instabilities driven by diffusion lead to the emergence of steady-state spatial patterns from random initial conditions and that bulk diffusion can suppress spatial patterns, in which case temporal oscillations can ensue. We include an extension of our framework that accounts for mechanochemical coupling when the bulk region is occupied by a deformable solid.

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!095

Catalyst-modified magnesium hydride (MgH2) holds the greatest promise as a solid-state hydrogen storage medium for mobile and stationary applications. However, the design and fabrication of highly active catalysts that enable MgH2 to reversibly desorb/absorb a large amount of hydrogen still remains challenging. In this work, a novel nanostructured ZrFe2 (nano-ZrFe2) measuring 30-120 nm in size was designed and fabricated as a catalyst precursor, which was readily converted into ultrafine ZrH2 and metallic Fe nanoparticles upon ball milling with MgH2 and first de-/hydrogenation, consequently delivering quite high catalytic activity for hydrogen storage in MgH2. MgH2 containing 10 wt% nano-ZrFe2 desorbed 6.2 wt% of H2 starting from approximately 193 °C, which was lowered by 35 °C with respect to the micron-ZrFe2-modified MgH2 (∼228 °C). When operated at a hydrogen pressure of 50 bars, the dehydrogenated sample absorbed ∼5.3 wt% of H2 at 200 °C within 30 minutes. The remarkably improved kinetic properties of MgH2 are mainly attributed to the ultrasmall nanoparticles and uniform, dispersive distribution of in situ formed ZrH2 and Fe. Such in situ conversion of nano-ZrFe2 not only provided a multiphase and multiscale catalytic environment that enabled high reactivity and catalytic activity but also facilitated H diffusion owing to increased interfaces, consequently promoting the dissociation and recombination of H2 molecules. These important insights in the new nanoscaled intermetallics broaden the scope of the design and synthesis of much higher active catalysts for hydrogen storage in light-metal hydrides, especially in MgH2 © 2024 The Royal Society of Chemistry.

Catalyst-modified magnesium hydride (MgH2) holds the greatest promise as a solid-state hydrogen storage medium for mobile and stationary applications. In this work, a novel nanostructured ZrFe2 (nano-ZrFe2) measuring 30-120 nm in size was designed and fabricated as a catalyst precursor, which was readily converted into ultrafine ZrH2 and metallic Fe nanoparticles upon ball milling with MgH2 and first de-/hydrogenation, consequently delivering quite high catalytic activity for hydrogen storage in MgH2.

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!096

In this paper, using density functional theory (DFT), we investigate the impact of mechanical treatment in terms of uniaxial and biaxial strains on both hydrogenation states of magnesium compounds i.e. H2-free magnesium (Mg) and preliminarily hydrogenated magnesium (MgH2). The thermodynamic properties calculation shows that applying uniaxial and biaxial strains on the H2-free magnesium does not significantly affect the formation enthalpy and decomposition temperature of the hydride phase. On the other hand, strain energy contributions on preliminarily hydrogenated magnesium are found able to decrease and improve the formation enthalpy and the decomposition temperature, making it feasible for the operational conditions of proton exchange membrane (PEM) fuel cells at 289 – 393 K. Also, the findings demonstrate that the kinetic properties in terms of hydrogen atom diffusion show a decrease in the activation energy barrier, which means an improvement in the kinetics properties faster than that of strain-free magnesium hydride. These results potentially provide better clues for the development of a magnesium-based metal hydride for hydrogen storage applications. © 2023 Hydrogen Energy Publications LLC

In this paper, using density functional theory (DFT), we investigate the impact of mechanical treatment in terms of uniaxial and biaxial strains on both hydrogenation states of magnesium compounds i.e. H2-free magnesium (Mg) and preliminarily hydrogenated magnesium (MgH2). These results potentially provide better clues for the development of a magnesium-based metal hydride for hydrogen storage applications.

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!097

Magnesium hydrides (MgH2) have drawn a lot of interest as a promising hydrogen storage material option due to their good reversibility and high hydrogen storage capacity (7.60 wt.%). However, the high hydrogen desorption temperature (more than 400 °C) and slow sorption kinetics of MgH2 are the main obstacles to its practical use. In this research, nickel zinc oxide (Ni0.6Zn0.4O) was synthesized via the solid-state method and doped into MgH2 to overcome the drawbacks of MgH2. The onset desorption temperature of the MgH2–10 wt.% Ni0.6Zn0.4O sample was reduced to 285 °C, 133 °C, and 56 °C lower than that of pure MgH2 and milled MgH2, respectively. Furthermore, at 250 °C, the MgH2–10 wt.% Ni0.6Zn0.4O sample could absorb 6.50 wt.% of H2 and desorbed 2.20 wt.% of H2 at 300 °C within 1 h. With the addition of 10 wt.% of Ni0.6Zn0.4O, the activation energy of MgH2 dropped from 133 kJ/mol to 97 kJ/mol. The morphology of the samples also demonstrated that the particle size is smaller compared with undoped samples. It is believed that in situ forms of NiO, ZnO, and MgO had good catalytic effects on MgH2, significantly reducing the activation energy and onset desorption temperature while improving the sorption kinetics of MgH2. © 2023 by the authors.

Magnesium hydrides (MgH2) have drawn a lot of interest as a promising hydrogen storage material option due to their good reversibility and high hydrogen storage capacity (7.60 wt.%). It is believed that in situ forms of NiO, ZnO, and MgO had good catalytic effects on MgH2, significantly reducing the activation energy and onset desorption temperature while improving the sorption kinetics of MgH2.

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!098

Hydrogen as an energy carrier has shown promises for future energy infrastructure. Due to its light weight and explosive nature, hydrogen need to be stored in safe and efficient way. The storage in solid state materials has been proposed as the safest method, which can store hydrogen through chemical bonding. Among several studied materials so far, KSiH3 is one of the leading contender with a total hydrogen capacity of 4.3 wt %, which is more than what is offered by its rivals such as BCC hydrides or AB5 type hydrides. However, the high activation energy slows down the hydrogen charging/discharging rate and allow the working only at higher temperatures (∼200 °C). The kinetics of hydrogen absorption and desorption intensely improved by the addition of a catalyst. In this work, vanadium based catalysts are added to KSiH3 system to modify the surface and to enhance the kinetics of this system. Specially, V2O5 addition, as leading candidate among the studied catalyst, decreased the activation energy to 83 kJmol-1 from 142 kJ/mol for pristine KSi. KSiH3 system with catalyst V2O5 started desorbing at 100 °C and could achieve highest weight loss 3.7 wt % which is very close to theoretical value. No disproportionation phenomenon is detected which indicated that the reaction between KSiH3 and KSi is flawlessly reversible with a hydrogen storage capacity of 3.7 wt % H2. The XPS investigation suggested a partial reduction of +5 oxidation state (corresponding to V2O5) to metallic state, which is proposed as the possible cause of this improvement. © 2022 Hydrogen Energy Publications LLC

KSiH3 system with catalyst V2O5 started desorbing at 100 °C and could achieve highest weight loss 3.7 wt % which is very close to theoretical value. The XPS investigation suggested a partial reduction of +5 oxidation state (corresponding to V2O5) to metallic state, which is proposed as the possible cause of this improvement.

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!099

Although MgH2 has been widely regarded as a promising material for solid-state hydrogen storage, its high operating temperature and slow kinetics pose a major bottleneck to its practical application. Here, a nanocomposite catalyst with interfacial coupling and oxygen defects, Ni/CeO2, is fabricated to promote H2 desorption and absorption properties of MgH2. The interface of Ni/CeO2 contributes to both strong mechanical coupling towards stabilizing partial Ni and electronic coupling towards inducing a high concentration of oxygen vacancies in CeO2. Theoretical calculations evidence that CeO2 with oxygen vacancy assist Ni in weakening the energy of Mg-H bond as well as enhancing the adsorption energy of Ni upon hydrogen atoms, and the extent of this assistance surprisingly increases with increasing oxygen vacancies concentration. As a result, an impressive performance is achieved by MgH2-5 wt.% Ni/CeO2 with onset desorption temperature of only 165 °C, and it absorbs approximately 80% hydrogen in just 800 s at 125 °C. The generation mechanism of intermediate active species concerning Ni/CeO2 in different states has been analyzed for the first time, and the relationship between interfacial coupling and phase evolution has been elucidated. Therefore, a mechanism of the catalysis-assisting effect regarding oxygen defects is proposed. It is believed that this work provides a unique perspective on the mechanism of interfacial coupling and the generation of defects in composite catalysts. © 2023

As a result, an impressive performance is achieved by MgH2-5 wt.% Ni/CeO2 with onset desorption temperature of only 165 °C, and it absorbs approximately 80% hydrogen in just 800 s at 125 °C. Therefore, a mechanism of the catalysis-assisting effect regarding oxygen defects is proposed.

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!100

LiAlH4 is considered as a promising material for solid state hydrogen storage. However, the lack of reversibility along with sluggish kinetics hinders its practical application. In this paper, hollow carbon nanospheres (HCNs) were used as a porous scaffold to confine LiAlH4 via solvent impregnation method. Nanoconfined LiAlH4 (LiAlH4@HCNs) exhibited significant improvements in hydrogen sorption compared to its bulk counterpart. LiAlH4@HCNs releases hydrogen sharply at 146 °C with full conversion to LiH within 1.5 h. The desorbed material can also be regenerated back to some extent into LiAlH4 under 8 MPa H2 at 150 °C. Measurement of the pressure-composition isotherm suggests an alteration in the equilibrium state upon confinement of LiAlH4 in voids of a few nanometres and thus altered hydrogen thermodynamic paths. © 2022 Elsevier B.V.

However, the lack of reversibility along with sluggish kinetics hinders its practical application. In this paper, hollow carbon nanospheres (HCNs) were used as a porous scaffold to confine LiAlH4 via solvent impregnation method.

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