Datasets:

Sharukesh
/

Solid_state_hydrogen_storage

Dataset card Viewer Files Files and versions Community

Split (1)

train · 515 rows

Id stringlengths 4 4	Abstract stringlengths 23 5.63k	Summary stringlengths 23 882	Unnamed: 3 stringclasses 1 value
!101	This study aims to present the hydro-catalytic treatment of organoamine boranes for efficient thermal dehydrogenation for hydrogen production. Organoamine boranes, methylamine borane (MeAB), and ethane 1,2 diamine borane (EDAB), known as ammonia borane (AB) carbon derivatives, are synthesized to be used as a solid-state hydrogen storage medium. Thermal dehydrogenation of MeAB and EDAB is performed at 80 °C, 100 °C, and 120 °C under different conditions (self, catalytic, and hydro-catalytic) for hydrogen production and compared with AB. For this purpose, a cobalt-doped activated carbon (Co-AC) catalyst is fabricated. The physicochemical properties of Co-AC catalyst is investigated by well-known techniques such as ATR/FT-IR, XRD, XPS, ICP-MS, BET, and TEM. The synthesized Co-AC catalyst obtained in nano CoOOH structure (20 nm, 12% Co wt) is formed and well-dispersed on the activated carbon support. It has indicated that Co-AC exhibits efficient catalytic activity towards organoamine boranes thermal dehydrogenation. Hydrogen release tests show that hydro-catalytic treatment improves the thermal dehydrogenation kinetics of neat MeAB, EDAB, and AB. Co-AC catalyzed hydro-treatment for thermal dehydrogenation of MeAB and EDAB acceleras the hydrogen release from 0.13 mL H2/min to 46.12 mL H2/min, from 0.16 mL H2/min to 38.06 mL H2/min, respectively at 80 °C. Moreover, hydro-catalytic treatment significantly lowers the H2 release barrier of organoamine boranes thermal dehydrogenation, from 110 kJ/mol to 19 kJ/mol for MeAB and 130 kJ/mol to 21 kJ/mol for EDAB. In conclusion, hydro and catalytic treatment presents remarkable synergistic effect in thermal dehydrogenation and improves the hydrogen release kinetics. © 2021 Hydrogen Energy Publications LLC	The physicochemical properties of Co-AC catalyst is investigated by well-known techniques such as ATR/FT-IR, XRD, XPS, ICP-MS, BET, and TEM. Hydrogen release tests show that hydro-catalytic treatment improves the thermal dehydrogenation kinetics of neat MeAB, EDAB, and AB.	_
!102	Solid-state hydrogen storage based on metal hydrides is considered a promising method for hydrogen storage. However, the low inherent thermal conductivity of metal hydride powder significantly limits the hydrogenation/dehydrogenation process in the metal hydride bed. Accurate measurement and improvement of the effective thermal conductivity of a hydride bed is of great significance for design of solid-state hydrogen storage devices. This article analyzes the factors that influence the effective thermal conductivity of a metal hydride bed, and also introduces different measurement methods and improvement ways for the effective thermal conductivity of a metal hydride bed. It is an effective way to improve the thermal conductivity of metal hydride beds by hydride powder mixed with a high thermal conductivity material and compaction. Accurately measuring the influence of hydrogen pressure, temperature and hydrogen storage capacity and other factors on the effective thermal conductivity of a metal hydride bed and obtaining the numerical equation of effective thermal conductivity play an important role in guiding the optimization design of heat and mass transfer structure of metal hydride hydrogen storage devices. The transient plane source method seems to be a better measurement choice because of short test time and easy to establish a pressure-tight and temperature control test system. However, there is still a lack of testing standards for the thermal conductivity of the hydride bed, as well as suggestions for the selection of test methods, improvement ways and design of in situ test room. © 2022 The Royal Society of Chemistry.	It is an effective way to improve the thermal conductivity of metal hydride beds by hydride powder mixed with a high thermal conductivity material and compaction. The transient plane source method seems to be a better measurement choice because of short test time and easy to establish a pressure-tight and temperature control test system.	_
!103	Humanity is confronted with one of the most significant challenges in its history. The excessive use of fossil fuel energy sources is causing extreme climate change, which threatens our way of life and poses huge social and technological problems. It is imperative to look for alternate energy sources that can replace environmentally destructive fossil fuels. In this scenario, hydrogen is seen as a potential energy vector capable of enabling the better and synergic exploitation of renewable energy sources. A brief review of the use of hydrogen as a tool for decarbonizing our society is given in this work. Special emphasis is placed on the possibility of storing hydrogen in solid-state form (in hydride species), on the potential fields of application of solid-state hydrogen storage, and on the technological challenges solid-state hydrogen storage faces. A potential approach to reduce the carbon footprint of hydrogen storage materials is presented in the concluding section of this paper. © 2021 by the author.	Humanity is confronted with one of the most significant challenges in its history. It is imperative to look for alternate energy sources that can replace environmentally destructive fossil fuels.	_
!104	LiBH4 as a promising candidate material for solid-state hydrogen storage still suffers from high dehydrogenation temperature and poor reversibility. A catalyzed LiBH4-based system with in situ introduced Li3BO3 and V is synthesized by adding NH4VO3 into LiBH4 followed by a heat treatment and a hydrogenation process. The optimized LiBH4 system introduced with 0.06 molar fraction of Li3BO3 + V, which is denoted as LiBH4–0.06LiBOV, shows excellent hydrogen storage kinetics and high reversible stability. The system starts to release hydrogen at 220 °C, and a capacity of 5.8 wt % H2 is obtained at 350 °C within 90 min. Furthermore, full rehydrogenation can be achieved at 500 °C and 50 bar of H2 for 50 min, and a capacity retention as high as 87.5% is obtained after five cycles. In situ introduced Li3BO3 and V lower the activation energy of LiBH4 and inhibit the generation of Li2B12H12 during the hydrogenation of LiBH4, which contribute to the synergistic catalytic effects on hydrogen desorption and absorption. In addition, the restraining of the particle size growth during dehydrogenation/hydrogenation is critical to inhibiting the generation of Li2B12H12 and thus improves the hydrogenation property of LiBH4. The catalyzed LiBH4 system provides new insights on LiBH4 as a high-density hydrogen storage material. © 2022 American Chemical Society	LiBH4 as a promising candidate material for solid-state hydrogen storage still suffers from high dehydrogenation temperature and poor reversibility. The optimized LiBH4 system introduced with 0.06 molar fraction of Li3BO3 + V, which is denoted as LiBH4–0.06LiBOV, shows excellent hydrogen storage kinetics and high reversible stability.	_
!105	Metallic hydride clusters have greater importance due to its unique physicomechanical properties. For solid-state hydrogen storage, (HfH2)n clusters has been considered a promising candidate because of high hydrogen capacity, low cost and larger interacting affinity between atoms. The structural and electronic properties of (HfH2)n clusters are investigated by employing the density functional theory. From the DFT calculations, it is found that Hf atom occupies central position while H atoms tends to occupy at vertex spots. Through structural stability analysis, the calculated binding energy and second order energy difference of (HfH2)n clusters increases from (HfH2)5 through (HfH2)30. The charge density distribution and results of Bader analysis revealed ionic bonding character between Hf and H atoms and transfer of electrons is observed from Hf to H atoms. The orbital overlapping contribution of the interacting Hf and H atom is also performed. © 2021 Elsevier B.V.	Metallic hydride clusters have greater importance due to its unique physicomechanical properties. From the DFT calculations, it is found that Hf atom occupies central position while H atoms tends to occupy at vertex spots.	_
!106	A ball milling technique was used to prepare a 4MgH2-LiAlH4 doped TiO2 sample. The hydrogen storage behaviour of the system 4MgH2-LiAlH4-TiO2 and the role played by TiO2 have been systematically investigated. The result shows the decrement of the initial decomposition temperature from the 4MgH2-LiAlH4-TiO2 composite when contrasted with the 4MgH2-LiAlH4 system. The initial dehydrogenation temperature of 4MgH2-LiAlH4-10 wt% TiO2 destabilized system decreased from 100°C and 270°C of undoped composite to 70°C and 200°C, respectively, for the desorption process in the first two stages. It was also found that the re/dehydrogenation kinetics performances of the 4MgH2-LiAlH4-10 wt% TiO2 destabilized system was improved when contrasted with the non-catalyzed sample. On the other hand, the activation energy for the MgH2-relevant decomposition is reduced from 133.3 kJ/mol (4MgH2-LiAlH4 sample) to 102.5 kJ/mol (4MgH2-LiAlH4-TiO2 sample). In addition, this synergistic effect of TiO2 on the improvement of the absorption/desorption performances was related to the formation of Al3Ti and TiH2 phases in the doped sample upon desorption, which reinforces the interaction of MgH2 with LiAlH4. This further changes the thermodynamics of the reactions by modifying the absorption/desorption pathway. In conclusion, the TiO2 catalyst showed a good catalytic impact in ameliorating the hydrogen sorption behaviour of the 4MgH2-LiAlH4 sample. © 2021 John Wiley & Sons Ltd	The initial dehydrogenation temperature of 4MgH2-LiAlH4-10 wt% TiO2 destabilized system decreased from 100°C and 270°C of undoped composite to 70°C and 200°C, respectively, for the desorption process in the first two stages. It was also found that the re/dehydrogenation kinetics performances of the 4MgH2-LiAlH4-10 wt% TiO2 destabilized system was improved when contrasted with the non-catalyzed sample.	_
!107	Hydrogen energy is a very attractive option in dealing with the existing energy crisis. For the development of a hydrogen energy economy, hydrogen storage technology must be improved to over the storage limitations. Compared with traditional hydrogen storage technology, the prospect of hydrogen storage materials is broader. Among all types of hydrogen storage materials, solid hydrogen storage materials are most promising and have the most safety security. Solid hydrogen storage materials include high surface area physical adsorption materials and interstitial and non-interstitial hydrides. Among them, interstitial hydrides, also called intermetallic hydrides, are hydrides formed by transition metals or their alloys. The main alloy types are A2B, AB, AB2, AB3, A2B7, AB5, and BCC. A is a hydride that easily forms metal (such as Ti, V, Zr, and Y), while B is a non-hydride forming metal (such as Cr, Mn, and Fe). The development of intermetallic compounds as hydrogen storage materials is very attractive because their volumetric capacity is much higher (80-160 kgH2m-3) than the gaseous storage method and the liquid storage method in a cryogenic tank (40 and 71 kgH2m-3). Additionally, for hydrogen absorption and desorption reactions, the environmental requirements are lower than that of physical adsorption materials (ultra-low temperature) and the simplicity of the procedure is higher than that of non-interstitial hydrogen storage materials (multiple steps and a complex catalyst). In addition, there are abundant raw materials and diverse ingredients. For the synthesis and optimization of intermetallic compounds, in addition to traditional melting methods, mechanical alloying is a very important synthesis method, which has a unique synthesis mechanism and advantages. This review focuses on the application of mechanical alloying methods in the field of solid hydrogen storage materials. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.	Additionally, for hydrogen absorption and desorption reactions, the environmental requirements are lower than that of physical adsorption materials (ultra-low temperature) and the simplicity of the procedure is higher than that of non-interstitial hydrogen storage materials (multiple steps and a complex catalyst). In addition, there are abundant raw materials and diverse ingredients.	_
!108	Ordered mesoporous carbon materials offer robust network of organized pores for energy storage and catalysis applications, but suffer from time-consuming and intricate preparations hindering their widespread use. Here we report a new and rapid synthetic route for a N-doped ordered mesoporous carbon structure through a preferential heating of iron oxide nanoparticles by microwaves. A nanoporous covalent organic polymer is first formed in situ covering the hard templates of assembled nanoparticles, paving the way for a long-range order in a carbonaceous nanocomposite precursor. Upon removal of the template, a well-defined cubic mesoporous carbon structure was revealed. The ordered mesoporous carbon was used in solid state hydrogen storage as a host scaffold for NaAlH4, where remarkable improvement in hydrogen desorption kinetics was observed. The state-of-the-art lowest activation energy of dehydrogenation as a single step was attributed to their ordered pore structure and N-doping effect. © 2021 Wiley-VCH GmbH	Upon removal of the template, a well-defined cubic mesoporous carbon structure was revealed. The state-of-the-art lowest activation energy of dehydrogenation as a single step was attributed to their ordered pore structure and N-doping effect.	_
!109	Hydrogen storage materials with high hydrogen capacity and low operating temperature had attracted intense interests for solid state hydrogen storage application. Sodium alanate (NaAlH4) with suitable thermodynamics and relatively high capacity was one of the most promising hydrogen storage materials for practical applications. However, high kinetic barriers induced high operating temperature, slow hydrogen release/uptake rate and poor reversibility. Considerable studies revealed that the addition of Ti-based catalysts could effectively improve its kinetic performance, consequently reducing the de-/hydrogenation temperature and enhancing the hydrogen storage reversibility. In this work, recent research progress of hydrogen storage properties of NaAlH4 modified by Ti-based catalysts was reviewed to guide the future development of this hydrogen storage system. First, the doping methods of Ti-based catalysts were introduced. After that, the improvement in hydrogen storage performance of NaAlH4 with various Ti-based catalysts was summarized and the corresponding catalytic mechanisms were elucidated. Finally, the future research direction of catalyst-modified NaAlH4 was discussed. It was well known that the addition process of catalysts was closely related to its existing state and distribution in metal hydride matrix, which affected the catalytic functions. High-energy ball milling treatment not only reduced the particle sizes of catalysts and NaAlH4 but also increased the uniform distribution of catalysts and intimate contact with NaAlH4 caused by energetic collision between milling balls. This facilitated the high catalytic activity. As a result, high-energy ball milling was the most frequently used and effective preparation strategy for catalyst-modified NaAlH4-based hydrogen storage materials. For optimizing catalysts, a variety of Ti-based compounds, including Ti-based organic compounds, halides, oxides and intermetallics, were studied and evaluated for their catalytic activity. Their effects on hydrogen storage behaviors of NaAlH4 were compared and the corresponding mechanisms were discussed and revealed. In particular, NaAlH4 catalyzed with ultrafine Ti nanoparticles supported on carbon displayed the best overall hydrogen storage properties. The usable hydrogen capacity remained at 5.07% and the on-set dehydrogenation temperature was reduced to 75℃. The dehydrogenated sample was fully hydrogenated within 3 min at 100℃ and 12.2 MPa of hydrogen pressure. More importantly, the capacity retention was as high as 98.6% after 100 cycles, which is quite favorable for practical applications. In addition, mechanistic studies revealed that high valent Ti-based compounds were reduced to low valent species and finally gave rise to the formation of Al-Ti or TiHx due to the strong reductivity of NaAlH4 during ball milling and initial dehydrogenation/hydrogenation cycling. The Al-Ti or TiHx species work as the actual active catalysts to promote the breaking and recombination of Al-H bonding. This was the most important reason for the reduced operating temperatures of dehydrogenation/hydrogenation. The key role played by Ti-based catalysts in the reduction of kinetic energy barriers for hydrogen release from NaAlH4 was further confirmed by theoretical calculations. The future studies should mainly focus on the synergistic effects of nanostructing and nano-catalysis to further improve the overall hydrogen storage properties of NaAlH4 materials. © Editorial Office of Chinese Journal of Rare Metals. All right reserved.	Sodium alanate (NaAlH4) with suitable thermodynamics and relatively high capacity was one of the most promising hydrogen storage materials for practical applications. As a result, high-energy ball milling was the most frequently used and effective preparation strategy for catalyst-modified NaAlH4-based hydrogen storage materials.	_
!110	The research progress of solid-state hydrogen storage technology is reviewed, including hydrogen storage materials, hydrogen storage devices and application status. Some hydrogen storage alloys have been successfully used in solid-state hydrogen storage devices. The high-capacity reversible hydrogen storage materials under mild hydrogen absorption and desorption conditions is the focus of current research and development. The optimized design of the hydrogen storage device effectively improves the rapid heat transfer characteristics and the safety performance. Hydrogen storage devices have been applied in the fields of distributed energy supply and motor vehicles. However, it is still necessary to further realize the coordination of rapid response, safety, reliability, and high hydrogen storage density of the hydrogen storage system. © 2022, Solar Energy Periodical Office Co., Ltd. All right reserved.	Hydrogen storage devices have been applied in the fields of distributed energy supply and motor vehicles. However, it is still necessary to further realize the coordination of rapid response, safety, reliability, and high hydrogen storage density of the hydrogen storage system.	_
!111	Reversible solid-state hydrogen storage is one of the key technologies toward pollutant-free and sustainable energy conversion. The composite system LiBH4-MgH2 can reversibly store hydrogen with a gravimetric capacity of 13 wt%. However, its dehydrogenation/hydrogenation kinetics is extremely sluggish (∼40 h) which hinders its usage for commercial applications. In this work, the kinetics of this composite system is significantly enhanced (∼96%) by adding a small amount of NbF5. The catalytic effect of NbF5 on the dehydrogenation/hydrogenation process of LiBH4-MgH2 is systematically investigated using a broad range of experimental techniques such as in situ synchrotron radiation X-ray powder diffraction (in situ SR-XPD), X-ray absorption spectroscopy (XAS), anomalous small angle X-ray scattering (ASAXS), and ultra/small-angle neutron scattering (USANS/SANS). The obtained results are utilized to develop a model that explains the catalytic function of NbF5 in hydrogen release and uptake in the LiBH4-MgH2 composite system. This journal is © The Royal Society of Chemistry.	Reversible solid-state hydrogen storage is one of the key technologies toward pollutant-free and sustainable energy conversion. The composite system LiBH4-MgH2 can reversibly store hydrogen with a gravimetric capacity of 13 wt%.	_
!112	Hydrogen storage technology plays an important role on the development of hydrogen fuel cell and lithium aluminum hydride is a powerful candidate for solid-state hydrogen storage materials. However, the high stability and slow dehydrogenation kinetics of LiAlH4 hinder its application. In this paper, the two-step thermal decomposition properties of LiAlH4 with and without Fe–Fe2O3 catalysts are investigated. According to the master plots, the model of mample power law (Pn) and nucleation and growth (An) are the optimal mechanism functions for the two-step decomposition of LiAlH4, respectively. After doping catalysts, the activation energies decrease significantly. The theoretical and optimized kinetic method are consistent with each other on activation energy. And the latter can also yield other kinetic parameters for a more comprehensive kinetic modelling of LiAlH4 decomposition. Furthermore, Fe–Al2O3 and Fe–Al intermetallics generated during dehydrogenation might significantly improve the hydrogen release properties of LiAlH4. © 2022	In this paper, the two-step thermal decomposition properties of LiAlH4 with and without Fe–Fe2O3 catalysts are investigated. Furthermore, Fe–Al2O3 and Fe–Al intermetallics generated during dehydrogenation might significantly improve the hydrogen release properties of LiAlH4.	_
!113	To run a sustainable society, hydrogen is considered as one of the most reliable option for clean and carbon free energy carrier. Hydrogen can be produced through several means using renewable energy sources, and can be stored either in solid, liquid or gaseous state. Though, compressed and liquefied hydrogen storages are well-established technologies in the commercial sector, however, due to the leakage risk, boil-off losses and explosive nature, world is exploring a safer way of hydrogen storage i.e. absorption/adsorption based solid-state hydrogen storage technology. The present review focuses mainly on the different material options available for the absorption based solid state hydrogen storage technology. The study reports insight view of different absorption material, broadly classified as metal hydrides and complex hydrides, with their hydrogen storage and reversible characteristics. The review also reports the tailoring properties of different hydrogen storage alloys and effect of element substitution on the absorption/desorption characteristics of a particular alloy. Key issues like effect of ball milling, annealing, doping, grain size, etc., on the alloy synthesis have been addressed. The review broadly summarizes the progress and recent worldwide advancement in the absorption based solid state hydrogen storage materials, synthesis and their hydrogenation/dehydrogenation mechanisms. © 2022 Elsevier Ltd	To run a sustainable society, hydrogen is considered as one of the most reliable option for clean and carbon free energy carrier. Key issues like effect of ball milling, annealing, doping, grain size, etc., on the alloy synthesis have been addressed.	_
!114	A 10 kg alloy mass metal hydride reactor, with LaNi5 alloy was designed. Heat transfer enhacement in the reactor was achieved by including embedded cooling tubes and an external water jacket. Detailed parametric study has been carried to understand the performance of the system. The effect of both geometrical and operational parameters was studied in simulations. The optimized geometrical parameters were used for fabricating the reactor. Experimental studies were carried on the fabricated reactor. Absorption studies were carried out for different supply pressure and different cooling fluid temperatures. Storage capacity of 1.13 wt% was found in 1620 s at a supply pressure of 25 bar and with a flow rate of 20 LPM. Similarily, desorption studies were carried out for varying heat transfer fluid temperatures. Complete and fastest desorption was observed at 80 °C with the reaction completion time of 2700 s. © 2020 Hydrogen Energy Publications LLC	Heat transfer enhacement in the reactor was achieved by including embedded cooling tubes and an external water jacket. Complete and fastest desorption was observed at 80 °C with the reaction completion time of 2700 s. © 2020 Hydrogen Energy Publications LLC	_
!115	Sluggish sorption kinetics, high decomposition temperature and unsatisfactory cycles of hydrogen release and uptake (reversibility) remain big challenges for using sodium alanate (NaAlH4) as a practical hydrogen storage medium. In solid-state hydrogen storage materials, especially NaAlH4, finding effective catalysts and using mechanical treatment represent promising solutions to overcome the drawbacks of NaAlH4. For the first time, in this work, the influence of spherical strontium titanate (SrTiO3) on the dehydrogenation behavior of NaAlH4 has been investigated. Here, we report that the onset desorption temperature is decreased and the desorption kinetics of NaAlH4 is enhanced with the addition of 10 wt% of spherical SrTiO3 catalyst. Using Kissinger's technique, the apparent activation energy of the NaAlH4 doped with 10 wt% SrTiO3 composites for the two-step dehydrogenation was identified as 79 and 92 kJ/mol, which was decreased significantly from that of undoped NaAlH4 (116 and 122 kJ/mol, respectively). Scanning electron microscopy results indicated that the NaAlH4 particle sizes decreased by milling with SrTiO3. X-ray diffraction results indicated that SrTiO3 did not react or change during the milling and desorption (heating) processes. The improvements in the desorption properties of NaAlH4 resulted from the ability of SrTiO3 to reduce the physical structure of the NaAlH4 during the ball milling process. © 2021 John Wiley & Sons Ltd	In solid-state hydrogen storage materials, especially NaAlH4, finding effective catalysts and using mechanical treatment represent promising solutions to overcome the drawbacks of NaAlH4. X-ray diffraction results indicated that SrTiO3 did not react or change during the milling and desorption (heating) processes.	_
!116	As the world is shifting toward an increased reliance on renewable energy, the need for effective and robust energy carriers is more than pressing. In this context, hydrogen has a key role to play. However, the storage of hydrogen in a cost-effective, safe, and compact manner is a bottleneck to the future hydrogen economy primarily due to the lack of incentives and technical difficulties in storing hydrogen. So far, materials capable of ambient hydrogen uptake/release have a low storage capacity while high-capacity hydrides that may offer more compact alternatives still rely on very high hydrogen release temperatures. This chapter summarizes the current potential of the solid-state hydrogen technology in the renewable energy sector and potential paths to engineer the next generation of materials along with their hydrogen thermodynamic and kinetic paths. © 2021 Elsevier Inc.	As the world is shifting toward an increased reliance on renewable energy, the need for effective and robust energy carriers is more than pressing. So far, materials capable of ambient hydrogen uptake/release have a low storage capacity while high-capacity hydrides that may offer more compact alternatives still rely on very high hydrogen release temperatures.	_
!117	Hydrogen stored in a solid state form of metal hydrides offers a safe and efficient storage technique for hydrogen application. In a closed metal hydride tank, stresses may occur on the tank wall due to hydride expansion during hydrogen absorption process. In the present investigation, a novel testing system for stress evolution of MlNi4.5Cr0.45Mn0.05 alloy in a closed cylindrical reactor during hydrogen absorption-desorption process was built. The results show that considerable swelling stress is developed on the inner reactor wall during activation process though a high free space of 45% is presented. Increasing hydrogen charging pressure and alloy loading fraction increase the as-generated swelling stress. The metal hydride particle expansion caused by hydrogen absorption is the intrinsic factor for swelling stress evolution. The presence of particle agglomerate in a closed tank in which its expansion is constrained is responsible for the observed swelling stress accumulation. © 2020 Hydrogen Energy Publications LLC	The results show that considerable swelling stress is developed on the inner reactor wall during activation process though a high free space of 45% is presented. Increasing hydrogen charging pressure and alloy loading fraction increase the as-generated swelling stress.	_
!118	TiFe intermetallic compound has been extensively studied, owing to its low cost, good volumetric hydrogen density, and easy tailoring of hydrogenation thermodynamics by elemental substitution. All these positive aspects make this material promising for large-scale applications of solid-state hydrogen storage. On the other hand, activation and kinetic issues should be amended and the role of elemental substitution should be further understood. This work investigates the thermodynamic changes induced by the variation of Ti content along the homogeneity range of the TiFe phase (Ti:Fe ratio from 1:1–1:0.9) and of the substitution of Mn for Fe between 0 and 5 at%. In all considered alloys, the major phase is TiFe-type together with minor amounts of TiFe2 or β-Ti-type and Ti4Fe2O-type at the Ti-poor and rich side of the TiFe phase domain, respectively. Thermodynamic data agree with the available literature but offer here a comprehensive picture of hydrogenation properties over an extended Ti and Mn compositional range. Moreover, it is demonstrated that Ti-rich alloys display enhanced storage capacities, as long as a limited amount of β-Ti is formed. Both Mn and Ti substitutions increase the cell parameter by possibly substituting Fe, lowering the plateau pressures and decreasing the hysteresis of the isotherms. A full picture of the dependence of hydrogen storage properties as a function of the composition will be discussed, together with some observed correlations. © 2021 Elsevier B.V.	TiFe intermetallic compound has been extensively studied, owing to its low cost, good volumetric hydrogen density, and easy tailoring of hydrogenation thermodynamics by elemental substitution. Thermodynamic data agree with the available literature but offer here a comprehensive picture of hydrogenation properties over an extended Ti and Mn compositional range.	_
!119	As a potential hydrogen storage material for solid hydrogen storage, the binary hydride MgH2 had the advantages of high hydrogen storage density and reversible hydrogen absorption and desorption. However, the applications of MgH2 were restricted due to the slow rate of hydrogen absorption and desorption, and the high working temperature. To date, in order to meet the requirements of solid hydrogen storage materials for vehicular hydrogen storage, many methods to improve the hydrogen storage performance of MgH2 were developed by scientific researchers such as alloying, nanocrystallization, and catalyst doping. These methods reduced the hydrogen desorption temperature of the system, increased the hydrogen absorption and desorption cycle stability. Among them, catalyst doping was the most extensively studied one, and it was considered to be a very effective way to improve the performance of magnesium-based hydrogen storage. A mechanical ball milling process was used to add the catalyst. During the ball milling process, the catalyst might react with the magnesium hydride in a solid state. Ball milling was a very important method of structural modification. It could not only conveniently control the composition of the alloy, but also could directly obtain materials with metastable structures such as nanocrystalline, amorphous and supersaturated solid solutions. In this method, metals (such as Fe, Co, Ni, Cu, etc.), metal compounds (such as Nb2O5, CeO2, TMTiO3 (TM=Ni, Co), etc.), transition metal halides (such as CeF4, CeF3, LaCl3, etc.), carbon-based materials (such as graphite, graphene, AC, CFs, etc.), metal-based and carbon-based composites were used as catalysts, and added single or in combination to magnesium-based alloys by mechanical ball milling. The research results showed that transition metals had a strong affinity for hydrogen atoms. During the dissociation of hydrogen molecules or the recombination of hydrogen atoms, the d electrons of transition metals and the electrons on the hydrogen atom/hydrogen molecular orbital were transferred and filled, which resulted in the interaction forces to promote the dissociation of hydrogen molecules and the recombination of hydrogen atoms. At the same time, after the metal catalyst was doped, many defects were generated on the surface of MgH2, which were conducive to charge and heat transfer. Furthermore, the metal oxides were cheap and easy to prepare. Doping transition metal oxides could effectively catalyze the hydrogen absorption and desorption reaction of MgH2. It could also be used as a lubricant and dispersant during the grinding process to prevent the agglomeration of MgH2 particles and refine the size of MgH2 particles, accelerate the hydrogen desorption kinetics of MgH2, catalyze the hydrogen absorption and desorption reaction of MgH2. Transition metal halides could react with MgH2 in the process of hydrogen absorption and desorption to generate transition metal hydrides. These transition metal hydrides could promote the dissociation of hydrogen molecules and the diffusion of hydrogen atoms, promote nucleation and reduction in the hydrogenation process. The reaction product of metal sulfide or metal hydride and MgH2 in the ball milling process had high catalytic activity, which could solve the problem of slow dehydrogenation/hydrogenation kinetics to a certain extent. In addition, MgS could provide abundant nucleation active sites, and Fe element could stabilize MgH2. LaF3 could react with Mg to form MgF2 and LaH3 phases during hydrogenation ball milling, which significantly increased the amount and rate of hydrogen desorption of magnesium. The catalytic mechanism was that LaH3 acted as a hydrogen pump. The addition of carbon-based materials could promote the nucleation of the Mg/MgH2 phase, refine the particle size, and improve the hydrogen absorption kinetics. Unfortunately, the effect was weaker than that of metal-based catalysts. Doped with metal-based and carbon-based composite catalysts, MgH2 could simultaneously obtain the effects of doped metal-based and carbon-based catalysts, such as the low dehydrogenation temperature, low dehydrogenation activation energy and excellent cycle stability. It could be seen that doped metal-based catalysts could generally promote the formation and decomposition of MgH2 bonds by generating a large number of defects or new phases, and then enhancing the dehydrogenation/hydrogenation kinetics of the hydrogen storage material system. Carbon-based materials doped with non-metals could effectively prevent MgH2 particles from agglomeration and grain growth during the ball milling process. In addition, its low density could maintain the high hydrogen storage capacity of MgH2 materials. In order to meet the practical standard, it was necessary to develop new technology and find new experimental methods. One of the important strategies to improve the hydrogen storage performance of MgH2 was synergistic utilization of metal-based materials and carbon-based materials as catalysts. To carry out composite catalysis research and to study the synergistic effect of different catalysts could help to improve the hydrogen storage performance of MgH2. With the help of simulation calculation or first principles, the mechanism of chemical reaction of MgH2 in the process of hydrogen absorption and desorption after catalyst doping could be further clarified. Therefore, the uniqueness and potential advantages of metal hydride hydrogen storage technology could be fully exploited. © Editorial Office of Chinese Journal of Rare Metals. All right reserved.	Carbon-based materials doped with non-metals could effectively prevent MgH2 particles from agglomeration and grain growth during the ball milling process. Therefore, the uniqueness and potential advantages of metal hydride hydrogen storage technology could be fully exploited.	_
!120	Density functional theory is adopted to study phase transitions, structural, elastic, and electronic properties of hydrogen storage K2PdH4. Firstly, the structural evolution of K2PdH4 is investigated under high pressure along with the hydrogen storage properties. In the ambient conditions, K2PdH4 crystallizes in a tetragonal structure with space group I4/mmm. As the pressure is increased gradually on the crystal, a phase transition is recorded to the orthorhombic structure with space group Immm. Subsequently, the density of states and electronic band structures are obtained for each phase. Mechanical properties such as ductility and brittleness are investigated using elastic constants which are crucial parameters for solid-state hydrogen storage materials. Moreover, several properties are analyzed using Young, shear and bulk modulus to reveal the bonding characteristics of K2PdH4 © S. Al and C. Kurkcu, 2021	Density functional theory is adopted to study phase transitions, structural, elastic, and electronic properties of hydrogen storage K2PdH4. Subsequently, the density of states and electronic band structures are obtained for each phase.	_
!121	Mg2Si is a promising catalyst for Mg-based H2 storage materials due to its low cost, light weight, and non-toxic properties. This study investigates the effects of Na in hypo-eutectic Mg-1wt.%Si alloys for H2 storage applications. The addition of trace amounts of Na is vital in improving the H2 sorption kinetics, achieving a H2 storage capacity of 6.72 wt.% H at 350 °C under 2 MPa H2, compared to 0.31 wt.% H in the non-Na added alloy. The hydrogen sorption mechanisms were analysed with Johnson-Mehl-Avrami-Kolmogorov models. It was identified that Na affects the surface of the Mg alloys, forming porous Na2O and NaOH in addition to MgO, facilitating the diffusion of H2. Finally, in-situ synchrotron powder X-ray diffraction showed the Mg2Si catalyst is stable during the H2 sorption reactions. This result demonstrates the potential use of Mg–Mg2Si casting alloys for large scale hydrogen storage and transportation applications. © 2022 Elsevier B.V.	Mg2Si is a promising catalyst for Mg-based H2 storage materials due to its low cost, light weight, and non-toxic properties. This result demonstrates the potential use of Mg–Mg2Si casting alloys for large scale hydrogen storage and transportation applications.	_
!122	High hydrogen density and low material costs make Mg as one of the most promising candidates for solid-state hydrogen storage. However, the practical applications of Mg are restricted by high reaction temperature and slow kinetics of hydrogen absorption/desorption. Here we present the improvements of both thermodynamics and kinetics of the hydride/deuteride of Mg (MgH2/MgD2) by utilizing the immiscible Mg–Cr system. Nanometer-sized MgD2 domains with the average crystallite size of ~10 nm embedded in a Cr matrix are formed in deuterated Mg0.25Cr0.75. X-ray diffraction and nuclear magnetic resonance spectroscopy studies show that the MgD2 domains are heavily distorted, which leads to the thermodynamic destabilization lowering the reaction temperature. Mg0.25Cr0.75 can reversibly absorb and desorb hydrogen/deuterium at a low temperature of 473 K. The enthalpy ΔH for deuterium desorption of Mg0.25Cr0.75−D is 72.1 kJ mol−1−D2, which is lower than ~74 kJ mol−1−D2 for bulk MgD2. The apparent activation energy for hydrogen desorption of Mg0.25Cr0.75−H is decreased to 75 kJ mol−1 from ~160 kJ mol−1 for bulk Mg, in which the dehydrogenation of nanometer-sized MgH2 is controlled by one-dimensional diffusion of hydrogen. Our work demonstrates that MgH2 nanostructured by an immiscible matrix is a useful strategy to alter the thermodynamic and kinetic properties. © 2021 Elsevier B.V.	Mg0.25Cr0.75 can reversibly absorb and desorb hydrogen/deuterium at a low temperature of 473 K. The enthalpy ΔH for deuterium desorption of Mg0.25Cr0.75−D is 72.1 kJ mol−1−D2, which is lower than ~74 kJ mol−1−D2 for bulk MgD2. Our work demonstrates that MgH2 nanostructured by an immiscible matrix is a useful strategy to alter the thermodynamic and kinetic properties.	_
!123	Hydrogen storage using the metal hydrides and complex hydrides is the most convenient method because it is safe, enables high hydrogen capacity and requires optimum operating condition. Metal hydrides and complex hydrides offer high gravimetric capacity that allows storage of large amounts of hydrogen. However, the high operating temperature and low reversibility hindered the practical implementation of the metal hydrides and complex hydrides. An approach of combining two or more hydrides, which are called reactive hydride composites (RHCs), was introduced to improve the performance of the metal hydrides and complex hydrides. The RHC system approach has significantly enhanced the hydrogen storage performance of the metal hydrides and complex hydrides by modifying the thermodynamics of the composite system through the metathesis reaction that occurred between the hydrides, hence enhancing the kinetic and reversibility performance of the composite system. In this paper, the overview of the RHC system was presented in detail. The challenges and perspectives of the RHC system are also discussed. This is the first review report on the RHC system for solid-state hydrogen storage. © 2021 Hydrogen Energy Publications LLC	Hydrogen storage using the metal hydrides and complex hydrides is the most convenient method because it is safe, enables high hydrogen capacity and requires optimum operating condition. An approach of combining two or more hydrides, which are called reactive hydride composites (RHCs), was introduced to improve the performance of the metal hydrides and complex hydrides.	_
!124	This paper details the process of designing, analysing, manufacturing, and testing an integrated solid-state hydrogen storage system. Analysis is performed to optimise flow distribution and pressure drop through the channels, and experimental investigations compare the effects of profile shape on the overall power output from the fuel cell. The storing of hydrogen is given much attention in the selection of a storage medium, and the effect of a cooling system to reduce the recharging time of the hydrogen storage vessel. The PTFE seal performed excellently, holding pressure over 60 bar, despite requiring changing each time the cell is opened. The assembly of the vessel was simple and straightforward, and there was no indication of pressure damage owing to the FEA analysis that was performed. The cooling chamber, although producing minor leaks due to design oversight, increased performance dramatically, showing a reduction in internal powder temperature from 130°C, down to 25°C during the absorption process, as well as reducing the absorption time down from 30 minutes to just over 5 minutes. The novel idea of implanting a sheathed thermocouple into the centre of the hydride powder proved to be highly valuable asset and provided important information, especially during desorption where the outside container could be heating up, while the inner powder is still cooling down, data that have not been seen before. © 2021 John Wiley & Sons Ltd.	This paper details the process of designing, analysing, manufacturing, and testing an integrated solid-state hydrogen storage system. The cooling chamber, although producing minor leaks due to design oversight, increased performance dramatically, showing a reduction in internal powder temperature from 130°C, down to 25°C during the absorption process, as well as reducing the absorption time down from 30 minutes to just over 5 minutes.	_
!125	Slow hydrogenation kinetics and high de/absorption temperature of Mg/MgH2 still a challenge in solid state hydrogen storage systems for industrial and automobile applications. The effect of PdCl2 on the hydrogenation properties including kinetics of Mg/MgH2 has been investigated in the present study. The nanocomposites of Mg and PdCl2 were prepared using Ball Mill method with different concentrations of PdCl2. The synthesized nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), pressure-composition-isotherm (PCI) and differential scanning calorimetry (DSC). The result indicates that the maximum hydrogen storage capacity were achieved 6.15 wt% for Mg-5 wt% PdCl2 nanocomposites, while milled Mg only absorb 3.417 wt% H2 at 300 °C. The desorption kinetics not so much improved with PdCl2 concentration. It is concluded that the onset temperature of Mg-PdCl2 nanocomposites shifted towards lower side than milled Mg using DSC analysis. The SEM and XRD patterns confirm the phase identity maintain during ball milling. The new phases of PdH0.778, MgCl2, Mg6Pd and various phases of MgH2 in MgH2-PdCl2 nanocomposites were confirmed on the basis of XRD analysis and reported data of the sample. © 2022 Elsevier Ltd	The desorption kinetics not so much improved with PdCl2 concentration. It is concluded that the onset temperature of Mg-PdCl2 nanocomposites shifted towards lower side than milled Mg using DSC analysis.	_
!126	The current energy transition imposes a rapid implementation of energy storage systems with high energy density and eminent regeneration and cycling efficiency. Metal hydrides are potential candidates for generalized energy storage, when coupled with fuel cell units and/or batteries. An overview of ongoing research is reported and discussed in this review work on the light of application as hydrogen and heat storage matrices, as well as thin films for hydrogen optical sensors. These include a selection of single-metal hydrides, Ti–V(Fe) based intermetallics, multi-principal element alloys (high-entropy alloys), and a series of novel synthetically accessible metal borohydrides. Metal hydride materials can be as well of important usefulness for MH-based electrodes with high capacity (e.g. MgH2 ~ 2000 mA h g−1) and solid-state electrolytes displaying high ionic conductivity suitable, respectively, for Li-ion and Li/Mg battery technologies. To boost further research and development directions some characterization techniques dedicated to the study of M-H interactions, their equilibrium reactions, and additional quantification of hydrogen concentration in thin film and bulk hydrides are briefly discussed. © 2020 Hydrogen Energy Publications LLC	Metal hydrides are potential candidates for generalized energy storage, when coupled with fuel cell units and/or batteries. Metal hydride materials can be as well of important usefulness for MH-based electrodes with high capacity (e.g. MgH2 ~ 2000 mA h g−1) and solid-state electrolytes displaying high ionic conductivity suitable, respectively, for Li-ion and Li/Mg battery technologies.	_
!127	Hydrogen energy, with environment amicable, renewable, efficiency, and cost-effective advantages, is the future mainstream substitution of fossil-based fuel. However, the extremely low volumetric density gives rise to the main challenge in hydrogen storage, and therefore, exploring effective storage techniques is key hurdles that need to be crossed to accomplish the sustainable hydrogen economy. Hydrogen physically or chemically stored into nanomaterials in the solid-state is a desirable prospect for effective large-scale hydrogen storage, which has exhibited great potentials for applications in both reversible onboard storage and regenerable off-board storage applications. Its attractive points include safe, compact, light, reversibility, and efficiently produce sufficient pure hydrogen fuel under the mild condition. This review comprehensively gathers the state-of-art solid-state hydrogen storage technologies using nanostructured materials, involving nanoporous carbon materials, metal-organic frameworks, covalent organic frameworks, porous aromatic frameworks, nanoporous organic polymers, and nanoscale hydrides. It describes significant advances achieved so far, and main barriers need to be surmounted to approach practical applications, as well as offers a perspective for sustainable energy research. Copyright © 2021 Jie Zheng et al.	Hydrogen energy, with environment amicable, renewable, efficiency, and cost-effective advantages, is the future mainstream substitution of fossil-based fuel. Its attractive points include safe, compact, light, reversibility, and efficiently produce sufficient pure hydrogen fuel under the mild condition.	_
!128	Rapid scale-up of the technologies for clean energy production, conversion and storage have been adopted by many countries in order to reduce demand for fossil fuels. Primary renewable energy such as solar, wind, and hydro are developed for energy production particularly for electricity generation. However, there are still some deficiencies in direct use of primary renewable energy sources; therefore, secondary energy sources (or carriers) have been recently established as clean energy sources. Hydrogen is a type of secondary energy sources with almost low density and light weight; therefore, it must be stored in the form of liquid or gas. The storage of hydrogen in the form of liquid requires very low temperature. Solid-state hydrogen storage on the surfaces of solids or within solids is a promising solution to above shortcomings for high-density energy storage. Herein, multi-layers solid-state materials with ability of hydrogen adsorption are presented, for the first time, including “mixed metal oxide (MMO) nanostructures” and “silicate layers”. The MMO is CuCe2(MoO4)4 nanostructures which synthesized via Pechini method in front of various chelating agents such as trimesic acid, maleic acid, succinic acid, and malonic acid, while the silicate layer is nanoclay montmorillonite K10. In this study, the experimental observations reveal a pure formation of CuCe2(MoO4)4 nanostructures in malonic acid at 500 °C, with almost regular nanosized morphology of 20–25 nm. The selected sample is then used for nanocomposite formation by dispersing the CuCe2(MoO4)4 nanostructures into the montmorillonite K10 solution. The final nanocomposites exhibit a superior electrochemical hydrogen storage performance, in terms of “maximum discharge capacity of ∼ 3750 mAh/g)” and “efficiency of about 70%” in an alkaline medium. It must be mentioned that though the maximum discharge capacity of the CuCe2(MoO4)4 nanostructures is higher than nanocomposites (for example ∼ 6000 mAh/g), but the efficiency (discharge/charge) is lower (∼48%). It can be emphasized that this nanocomposite can be applied as promising host in an electrochemical hydrogen storage system, which can meet the U.S. Department of Energy (DOE) hydrogen storage targets. © 2021 Elsevier Ltd	Hydrogen is a type of secondary energy sources with almost low density and light weight; therefore, it must be stored in the form of liquid or gas. Herein, multi-layers solid-state materials with ability of hydrogen adsorption are presented, for the first time, including “mixed metal oxide (MMO) nanostructures” and “silicate layers”.	_
!129	LiAlH4 is regarded as a potential material for solid-state hydrogen storage because of its high hydrogen content (10.5 wt%). However, its high decomposition temperature, slow dehydrogenation kinetics and irreversibility under moderate condition hamper its wider applications. Mechanical milling treatment and doping with a catalyst or additive has drawn significant ways to improve hydrogen storage properties of LiAlH4. Microstructure or nanostructure materials were developed by using a ball milling technique and doping with various types of catalysts or additives which had dramatically improved the efficiency of LiAlH4. However, the state-of-the-art technologies is still far from meeting the expected goal for the applications. In this paper, the overview of the recent advances in catalyst-enhanced LiAlH4 for solid-state hydrogen storage is detailed. The remaining challenges and the future prospect of LiAlH4–catalyst system is also discussed. This paper is the first systematic review that focuses on catalyst-enhanced LiAlH4 for solid-state hydrogen storage. © 2021 Hydrogen Energy Publications LLC	Mechanical milling treatment and doping with a catalyst or additive has drawn significant ways to improve hydrogen storage properties of LiAlH4. This paper is the first systematic review that focuses on catalyst-enhanced LiAlH4 for solid-state hydrogen storage.	_
!130	Magnesium hydrides (MgH2) have attracted extensive attention as solid-state H2 storage, owing to their low cost, abundance, excellent reversibility, and high H2 storage capacity. This review comprehensively explores the synthesis and performance of Mg-based alloys. Several factors affecting their hydrogen storage performance were also reviewed. The metals addition led to destabilization of Mg–H bonds to boost the dehydrogenation process. A unique morphology could provide more available active sites for the dissociation/recombination of H2 and allow the activation energy reduction. Also, an appropriate support prevent the agglomeration of Mg particles, hence, sustains their nanosize particles. Moreover, the perspective of avenues for future research presented in this review is expected to act as a guide for the development of novel Mg-based H2 storage systems. New morphological shape of catalysts, more unexplored and highly potential waste materials, and numerous synthesis procedures should be explored to further enhance the H2 storage of Mg-based alloys. © 2021 Hydrogen Energy Publications LLC	Moreover, the perspective of avenues for future research presented in this review is expected to act as a guide for the development of novel Mg-based H2 storage systems. New morphological shape of catalysts, more unexplored and highly potential waste materials, and numerous synthesis procedures should be explored to further enhance the H2 storage of Mg-based alloys.	_
!131	Energy is an essential requirement in our daily lives. Currently, most of our energy demands are fulfilled by fossil fuels. After 20 years, non-renewable fossil fuels are estimated to plummet rapidly. The world will face energy shortage and will seek for a new environmental method of energy generation for transportation, economy and application. Hydrogen is a fascinating energy carrier that is considered as ‘hydrogen economy’ for the future. The key challenge in developing the hydrogen economy is the context of hydrogen storage. Storing hydrogen via the solid-state method has received special attention and consideration because of its safety and larger storage capacity. A light complex hydride, NaAlH4, is considered as an attractive material for solid-state hydrogen storage owing to its high hydrogen capacity, bulk in availability and low cost. Sluggish sorption kinetics and poor reversibility have driven research into various catalysts to enhance its hydrogen storage properties. This review article examines the development of different catalysts and their effects on the hydrogen storage properties of NaAlH4. The addition of catalyst offers synergistic catalytic effect on the dehydrogenation performance of NaAlH4. Doping NaAlH4 with catalyst promote promising results such as lower decomposition temperature, improved kinetics and reduced activation energy. Superior performance on the dehydrogenation performance of NaAlH4 doping with the catalyst may be due to the nanosized catalyst particle and in situ formed active species that may serve as nucleation sites at the surface of the NaAlH4 matrix and benefiting the kinetics properties of NaAlH4. © 2020 Hydrogen Energy Publications LLC	Sluggish sorption kinetics and poor reversibility have driven research into various catalysts to enhance its hydrogen storage properties. Doping NaAlH4 with catalyst promote promising results such as lower decomposition temperature, improved kinetics and reduced activation energy.	_
!132	First principles calculations have been adopted to explore ground-state and high-pressure properties of KCaH3 and KSrH3 orthorhombic perovskite hydrides for the purpose of solid-state hydrogen storage. Formation enthalpies of materials, structural and mechanical properties, electronic and hydrogen storage properties are computed and examined. The computed formation enthalpies and phonon frequencies of KCaH3 and KSrH3 indicate dynamical stability at 0 GPa. The gravimetric hydrogen densities of KCaH3 and KSrH3 are found to be 3.55 wt% and 2.28 wt%, respectively. Also, the hydrogen desorption temperatures are calculated as 449 K and 394 K for KCaH3 and KSrH3. Elastic constants for each phase and several parameters derived from elastic constants are computed and evaluated, such as bulk and Shear modulus. The B/G ratios of materials depict that both KCaH3 and KSrH3 are brittle materials. The electronic properties show band gaps for both materials at 0 GPa, confirming an insulating nature and as pressure increases the band gap shrinks for KCaH3 and disappears for KSrH3. Graphical abstract: [Figure not available: see fulltext.]. © 2022, The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature.	First principles calculations have been adopted to explore ground-state and high-pressure properties of KCaH3 and KSrH3 orthorhombic perovskite hydrides for the purpose of solid-state hydrogen storage. © 2022, The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature.	_
!133	MgH2 is considered one of the most promising candidates for solid-state hydrogen storage. However, the dehydrogenation of MgH2 generally happens at temperatures above 250 °C even after catalyzing and/or nano-confining modifications, thus embarrassing the practical use of MgH2 in fuel cells. NH4Cl is a cheap chemical which has mature synthesis technologies in large industrial productions. The protonic H (Hδ+) in NH4Cl and the hydridic H (Hδ−) in MgH2 have coulomb interaction which allow MgH2 to release hydrogen at milder temperatures. In this article, by designing the molar ratio of MgH2 and NH4Cl as 2:1 (equal molar ratio of Hδ+ and Hδ−), the hydrogen release peak temperature can be decreased to 164.8 °C, and the ammonia generation is remarkably suppressed. In particular, graphene introduction to the 2MgH2+NH4Cl composite can further reduce the hydrogen release temperature to 161.2 °C and improve the hydrogen purity up to 97.26%. It is revealed that the smaller particle size and the better dispersion of 2MgH2+NH4Cl/graphene composite allows better interaction between Hδ+ and Hδ−, which brings down the hydrogen desorption temperature and improves the hydrogen purity. © 2021 Elsevier B.V.	MgH2 is considered one of the most promising candidates for solid-state hydrogen storage. NH4Cl is a cheap chemical which has mature synthesis technologies in large industrial productions.	_
!134	The on-board hydrogen storage needs light, compact, and affordable system to replace the compressed hydrogen tanks. MgH2 is regarded as one of the most promising candidates for solid-state hydrogen storage. Due to the thermodynamically stable Mg-H bond, the poor dissociation ability of H2 molecules and recombination ability of H atoms on Mg surface, and the low diffusion coefficient of H atoms in Mg, especially in MgH2, there remains a challenge to design a material capable of absorbing and desorbing hydrogen rapidly at moderate temperatures. Herein, common strategies to improve the hydrogen storage properties of Mg-based materials are introduced. Some recent studies for overcoming the thermodynamic and kinetic barriers are reviewed, especially the approaches to fabricate nanostructure in Mg-based materials. The nanometric crystals or particles are synthesized by mechanical deformation, reduction in solution, physical/chemical vapor deposition, interface confinement. The nano-catalyst can be decorated by external doping or in-situ synthesis. In particular, the thermodynamic/kinetic parameters for hydrogenation and dehydrogenation are provided, and the mechanisms for the enhanced properties are summarized. The principles of structural design and catalytic decoration are discussed, and challenges and perspectives of fabricating nanostructures in Mg-based hydrogen storage materials are proposed. © 2021 Elsevier B.V.	Herein, common strategies to improve the hydrogen storage properties of Mg-based materials are introduced. The nanometric crystals or particles are synthesized by mechanical deformation, reduction in solution, physical/chemical vapor deposition, interface confinement.	_
!135	Aluminum hydride (AlH3) is a binary metal hydride that contains more than 10.1 wt% of hydrogen and possesses a high volumetric hydrogen density of 148 kg H2 m−3. Pristine AlH3 can readily release hydrogen at a moderate temperature below 200 °C. Such high hydrogen density and low desorption temperature make AlH3 one of most promising hydrogen storage media for mobile application. This review covers the research activity on the structures, synthesis, decomposition thermodynamics and kinetics, regeneration and application validation of AlH3 over the past decades. Finally, the future research directions of AlH3 as a hydrogen storage material will be revealed. © 2020	Pristine AlH3 can readily release hydrogen at a moderate temperature below 200 °C. Finally, the future research directions of AlH3 as a hydrogen storage material will be revealed.	_
!136	In current research, solid-state materials are often used as the most promising materials for hydrogen storage materials in comparison of the other storage materials. Hydrogen is considered as an important source of energy storage system for automotive applications. Hydrogen as a conventional fuel offers high potential benefits due to their easily storage and transportation and considered as an alternative fuel because of its natural abundance and a clean and sustainable energy carrier. It is available in abundance and is the renewable sources of energy and, more significantly, is a clean fuel. Metal hydrides are able to store relatively large amounts of hydrogen in a solid phase as compared with other solid-state materials with safety and long-term stability. This perspective chapter highlights the brief idea about the various solid-state materials as storage of hydrogen and various applications in energy fields. © 2021 Elsevier Inc. All rights reserved.	Hydrogen is considered as an important source of energy storage system for automotive applications. Metal hydrides are able to store relatively large amounts of hydrogen in a solid phase as compared with other solid-state materials with safety and long-term stability.	_
!137	Safe, compact, lightweight and cost-effective hydrogen storage is one of the main challenges that need to be addressed to effectively deploy the hydrogen economy. LiAlH4, as a solid-state hydrogen storage material, presents several advantages such as high hydrogen storage capacity, low price and abundant sources. Unfortunately, neither thermodynamic nor kinetic properties of dehydrogenation for LiAlH4 can fulfill the requirements of practical application. Thus, a series of spinel ferrite nanoparticles such as XFe2O4 (X = Ni, Co, Mn, Cu, Zn, Fe) were prepared by using the modified thermal decomposition method, and then doped into LiAlH4 by using ball milling. Our results show that LiAlH4 doped with 7 wt% NiFe2O4 starts to release hydrogen at 69.1 °C, and the total amount of hydrogen released is 7.29 wt% before 300 °C. The activation energies of the two-step hydrogen release reactions of LiAlH4 doped with 7 wt% NiFe2O4 are 42.32 kJ mol−1 and 71.42 kJ mol−1, which are 59.0% and 63.6% lower than those of as-received LiAlH4, respectively. Combining the density functional theory (DFT) calculations, we reveal that both the presence of NiFe2O4 and in-situ formed Al4Ni3 in ball-milling decrease the desorption energy barrier of Al-H bonding in LiAlH4 and accelerate the breakdown of Al-H bonding through the interfacial charge transfer and the dehybridization of the Al-H cluster. Thus, the experimental and theoretical results open a new avenue toward designing high effective catalysts applied to LiAlH4 as a candidate for hydrogen storage. © 2021	Safe, compact, lightweight and cost-effective hydrogen storage is one of the main challenges that need to be addressed to effectively deploy the hydrogen economy. Thus, a series of spinel ferrite nanoparticles such as XFe2O4 (X = Ni, Co, Mn, Cu, Zn, Fe) were prepared by using the modified thermal decomposition method, and then doped into LiAlH4 by using ball milling.	_
!138	Despite the fact that the affinities of both palladium and magnesium with hydrogen have been studied for many years, information about magnesium-palladium alloys is still incomplete. Although palladium is an extremely expensive metal and magnesium palladium alloys will likely never applied as solid-state hydrogen storage materials, the interaction of these alloys with hydrogen may be useful for broadening knowledge or finding applications as hydrogen splitters, catalysts, and hydrogen sensors. In this work, two types of calorimetric techniques were applied to measure the thermodynamic properties of magnesium-rich alloys from the Mg-Pd system (containing 97.7; 85.4; 80.6; 79.9; 72.3; 70.7; 64.5 at% of Mg respectively). The solution calorimetric method was used to determine the heat of solution of liquid magnesium and palladium in liquid tin. Additionally, the standard enthalpies of formation of six alloys corresponding to the intermetallic phases of the Mg-rich region were measured. These alloys were prepared from pure Mg and Pd, which were melted in a glove box filled with high purity argon, with a very low concentration of impurities. All the obtained alloys were structurally analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM/EDS) methods. Moreover, DSC studies were used to determine the transformation temperatures in the Mg-rich region. The values of the standard formation enthalpy of the studied alloys were determined to be −27.3 ± 0.8 kJ/mol at., −33.4 ± 0.9 kJ/mol at., −35.2 ± 1.4 kJ/mol at., −44.2 ± 0.9 kJ/mol at., −46.0 ± 0.7 kJ/mol at., and −54.3 ± 2.3 kJ/mol at. These values were compared with the data calculated using the Miedema model, as well as with existing literature data for the Mg6Pd and Mg5Pd2 phases. © 2020 Elsevier B.V.	These alloys were prepared from pure Mg and Pd, which were melted in a glove box filled with high purity argon, with a very low concentration of impurities. All the obtained alloys were structurally analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM/EDS) methods.	_
!139	Hydrogen has the highest gravimetric density (energy density per unit mass) of any fuel. The combustion of hydrogen releases energy in the form of heat. When hydrogen reacts with oxygen in a fuel cell, the reaction releases energy in the form of electricity. Unlike hydrocarbon-based fuels, the generation of energy from either the combustion of hydrogen or the reaction of hydrogen with oxygen in a fuel cell is not accompanied by the emission of greenhouse gases. This makes hydrogen a promising solution to solve global warming issues. However, hydrogen has a low volumetric density (low energy density per unit volume) which makes storing or transporting hydrogen extremely difficult and expensive. To accelerate the utilization of hydrogen as an energy carrier, it is necessary to develop advanced hydrogen storage methods that have the potential to have a higher energy density. The hydrogen storage market is segmented by application into: (1) Stationary power: stored hydrogen is consumed for example in a fuel cell for use in backup power stations, refueling stations, power stations; (2) Portable power: hydrogen storage applications for electronic devices such as mobile phones, flash lights, and portable generators; and (3) Transportation: industries including automobiles, aerospace, unmanned aerial systems, and hydrogen tanks used throughout the hydrogen supply chain. The increasing development of light and heavy fuel cell vehicles is expected to drive the development of on-board solid-state hydrogen technologies. A large number of research groups worldwide for many years have been trying to develop materials having the right set of thermodynamic and kinetic properties, along with all of the physical properties (high gravimetric density, high volumetric density, etc.) to allow for low-pressure storage system in ambient conditions. However, to date, no material has been found that satisfies all the desired properties to be viably used in many applications. Even if we consider only three parameters namely gravimetric density, volumetric density, and system cost, no materials that can meet the ultimate targets of the U.S. Department of Energy (DOE) or the 2030 targets of the European Union's Fuel Cells and Hydrogen Joint Undertaking (FCH JU) and the New Energy and Industrial Technology Development Organization (NEDO) in Japan. The present article reviews advances in solid-state hydrogen storage technology and compares the opportunities and challenges of selected materials. The materials reviewed in this article have a wider spectrum than the materials reviewed in other existing articles, including carbon nanotubes (CNTs), metal–organic frameworks (MOFs), graphene, boron nitride (BN), fullerene, silicon, amorphous manganese hydride molecular sieve, and metal hydrides. Pioneering works, important breakthroughs, as well as the latest developments for promising materials are also reviewed. In addition, for the first time the targets set by several official regulatory agencies for solid-state hydrogen storage are summarized. Achievements in academic and industrial research are compared against these targets. The future prospects of promising materials are analyzed based on how its practical application can be implemented according to market needs. © 2022 Hydrogen Energy Publications LLC	The materials reviewed in this article have a wider spectrum than the materials reviewed in other existing articles, including carbon nanotubes (CNTs), metal–organic frameworks (MOFs), graphene, boron nitride (BN), fullerene, silicon, amorphous manganese hydride molecular sieve, and metal hydrides. The future prospects of promising materials are analyzed based on how its practical application can be implemented according to market needs.	_
!140	TiFe-based alloys are solid-state hydrogen storage materials operated at room temperature (RT). The current study presents a systematic approach for solving the activation issue (difficulty in the first hydrogenation), one of the major obstacles to the practical application of TiFe alloys, via the use of a secondary AB2 phase. Based on the Ti–Fe–Cr ternary phase diagram, Ti–Fe–Cr alloys containing 80 at% Ti(Fe,Cr) (AB phase) and 20 at% Ti(Fe,Cr)2 (AB2 phase) were designed; the Cr concentrations in the AB and AB2 phase were systematically varied while maintaining fixed phase fractions. Activation at RT was achieved when the overall Cr concentration was higher than 9.7 at%. Analysis of the activation characteristics of the individual phases revealed that the AB2 phase readily absorbed hydrogen, thereby initiating activation of AB + AB2 alloys. Notably, higher Cr concentrations enable the AB phase to absorb hydrogen at RT during the activation process, although the kinetics are much slower than that of the co-existing AB2 phase. The equilibrium hydrogen pressures from the pressure-composition isotherms decrease as the Cr concentration increases, indicating that Cr stabilizes hydrides. Increased hydride stability may also promote the kinetics of the initial hydride formation in both the AB and AB2 phases. An optimal composition for Ti–Fe–Cr alloys can be designed given the conditions of easy activation at RT and maximum reversible capacity within an operating pressure range. © 2021 Elsevier B.V.	TiFe-based alloys are solid-state hydrogen storage materials operated at room temperature (RT). An optimal composition for Ti–Fe–Cr alloys can be designed given the conditions of easy activation at RT and maximum reversible capacity within an operating pressure range.	_