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Fast forging of compacts made up of Mg and Ni powders is shown to be an effective method to induce severe plastic deformation with improved H2 sorption properties. Here, using such processed samples, a comprehensive analysis of the sorption properties reveals that the first hydrogenation sequence significantly depends on the forging temperature, through different microstructures. More in detail, no phase transformation occurs upon cold forging, while solid-state reaction leads to the formation of the Mg2Ni intermetallic compound upon forging above 400 °C. Forging below the brittle-to-ductile transition (225-250 °C) leads to faster H2 uptake upon first absorption owing to a more textured fiber along the c-axis and internal strains which promote hydrogen diffusion through the bulk material. Desorption kinetics remain slower with low-temperature forging, despite Ni recombining to form Mg2Ni during the first desorption. After several cycles, a two-step behavior is observed with a fast absorption step occurring up to about 3 wt.%. Despite this limited uptake performance, the forging process can be considered as a straightforward, safe, and cost-efficient process to produce large amounts of Mg-based alloys for hydrogen storage. In particular, such severe plastic deformation processes can be considered as reliable substitutes for ball-milling, which is highly efficient but energy- and time-consuming. © 2020 by the authors.

Despite this limited uptake performance, the forging process can be considered as a straightforward, safe, and cost-efficient process to produce large amounts of Mg-based alloys for hydrogen storage. In particular, such severe plastic deformation processes can be considered as reliable substitutes for ball-milling, which is highly efficient but energy- and time-consuming.

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The impact of boron doping on MgH2 bonding mechanism, hydrogen diffusion and desorption was calculated using density functional theory (DFT). Atomic interactions in doped and non-doped system and its influence on hydrogen and vacancy diffusion were studied in bulk hydride. Slab calculations were performed to study hydrogen desorption energies from (110) boron doped surface and its dependence on the surface configuration and depth position. To study kinetics of hydrogen diffusion in boron vicinity and hydrogen molecule desorption activation energies from boron doped and non-doped (110) MgH2 surface Nudged Elastic Band (NEB) method was used. Results showed that boron forms stronger, covalent bonds with hydrogen causing the destabilization in its first and second coordination. This leads to lower hydrogen desorption energies and improved hydrogen diffusion, while the impact on the energy barriers for H2 desorption from hydride (110) surface is less pronounced. © 2019 Hydrogen Energy Publications LLC

The impact of boron doping on MgH2 bonding mechanism, hydrogen diffusion and desorption was calculated using density functional theory (DFT). Results showed that boron forms stronger, covalent bonds with hydrogen causing the destabilization in its first and second coordination.

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β Ti–Nb BCC alloys are potential materials for hydrogen storage in the solid state. Since these alloys present exceptional formability, they can be processed by extensive cold rolling (ECR), which can improve hydrogen sorption properties. This work investigated the effects of ECR accomplished under an inert atmosphere on H2 sorption properties of the arc melted and rapidly solidified β Ti40Nb alloy. Samples were crushed in a rolling mill producing slightly deformed pieces within the millimeter range size, which were processed by ECR with 40 or 80 passes. Part of undeformed fragments was used for comparison purposes. All samples were characterized by scanning electron microscopy, x-ray diffractometry, energy-dispersive spectroscopy, hydrogen volumetry, and differential scanning calorimetry. After ECR, samples deformed with 40 passes were formed by thick sheets, while several thin layers composed the specimens after 80 passages. Furthermore, deformation of β Ti–40Nb alloys synthesized samples containing a high density of crystalline defects, cracks, and stored strain energy that increased with the deformation amount and proportionally helped to overcome the diffusion's control mechanisms, thus improving kinetic behaviors at low temperature. Such an improvement was also correlated to the synergetic effect of resulting features after deformation and thickness of stacked layers in the different deformation conditions. At the room temperature, samples deformed with 80 passes absorbed ∼2.0 wt% of H2 after 15 min, while samples deformed with 40 passes absorbed ∼1.8 wt% during 2 h, excellent results if compared with undeformed samples hydrogenated at 300 °C that acquired a capacity of ∼1.7 wt% after 2 h. The hydrogen desorption evolved in the same way as for absorption regarding the deformation amount, which also influenced desorption temperatures that were reduced from ∼270 °C, observed for the undeformed and samples deformed with 40 passes, to ∼220 °C, for specimens rolled with 80 passes. No significant loss in hydrogen capacity was observed in the cold rolled samples. © 2019 Hydrogen Energy Publications LLC

β Ti–Nb BCC alloys are potential materials for hydrogen storage in the solid state. Furthermore, deformation of β Ti–40Nb alloys synthesized samples containing a high density of crystalline defects, cracks, and stored strain energy that increased with the deformation amount and proportionally helped to overcome the diffusion's control mechanisms, thus improving kinetic behaviors at low temperature.

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Cluster-based materials are candidate materials for solid-state hydrogen storage owing to their special geometric and electronic structures. The surface adsorption and the encapsulated storage of H2 molecules in a cagelike (MgO)12 cluster have been studied using density functional theory (DFT) calculations including a dispersion interaction. The results revealed that the cagelike (MgO)12 cluster surface can adsorb 24 H2 molecules with an average adsorption energy of 0.116 eV/H2, which brings about a gravimetric density of 9.1 wt%. Compared with dispersion-corrected DFT calculations, the traditional DFT method substantially underestimates the surface adsorption strength. According to symmetric configurations, a maximum capacity of six H2 molecules can be stored in the interior space of the cagelike (MgO)12 cluster. The encapsulated H2 molecules are trapped by stepwise energy barriers of 0.433–2.550 eV, although the storage is an endothermic process. The present study will be beneficial for hydrogen storage in cagelike clusters and assembled porous materials. © 2018 Hydrogen Energy Publications LLC

The surface adsorption and the encapsulated storage of H2 molecules in a cagelike (MgO)12 cluster have been studied using density functional theory (DFT) calculations including a dispersion interaction. The present study will be beneficial for hydrogen storage in cagelike clusters and assembled porous materials.

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Hydrogen is considered as a propitious and sound alternative to fossil fuels. The current technologies allow hydrogen to be stored in the forms of gas, liquid, and solid. The solid-state hydrogen storage offers higher energy capacity with advantageous safety considerations. This chapter presents the current materials and technologies for hydrogen storage, which emphasized the solid-state form. These include various types of solid-state materials based on physisorption and chemisorption. In this chapter, different categories of materials such as binary hydrides, complex hydrides, and nanoconfinement are reviewed and discussed. Besides, hydrogen storage in the forms of compressed gas and liquid is presented in this chapter. © 2020 Elsevier Inc. All rights reserved.

Hydrogen is considered as a propitious and sound alternative to fossil fuels. These include various types of solid-state materials based on physisorption and chemisorption.

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Intermetallic TiMn2 compound was employed for improving the de/rehydrogenation kinetics behaviors of MgH2 powders. The metal hydride powders, obtained after 200 h of reactive ball milling was doped with 10 wt% TiMn2 powders and high-energy ball milled under pressurized hydrogen of 70 bar for 50 h. The cold-pressing technique was used to consolidate them into 36-green buttons with 12 mm in diameter. During consolidation, the hard TiMn2 spherical powders deeply embedded into MgH2 matrix to form homogeneous nanocomposite bulk material. The apparent activation energies of hydrogenation and dehydrogenation for the fabricated buttons were 19.3 kJ/mol and 82.9 kJ/mol, respectively. The present MgH2/10 wt% TiMn2 nanocomposite binary system possessed superior hydrogenation/dehydrogenation kinetics at 225 °C to absorb/desorb 5.1 wt% hydrogen at 10 bar/200 mbar H2 within 100 s and 400 s, respectively. This new system revealed good cyclability of achieving 414 cycles within 600 h continuously without degradations. For the present study, the consolidated buttons were used as solid-state hydrogen storage for feeding proton-exchange membrane fuel cell through a house made Ti-reactor at 250 °C. This nanocomposite system possessed good capability for providing the fuel cell with hydrogen flow at an average rate of 150 ml/min. The average current and voltage outputs were 3 A and 5.5 V, respectively. © 2019 Hydrogen Energy Publications LLC

The metal hydride powders, obtained after 200 h of reactive ball milling was doped with 10 wt% TiMn2 powders and high-energy ball milled under pressurized hydrogen of 70 bar for 50 h. The cold-pressing technique was used to consolidate them into 36-green buttons with 12 mm in diameter. This nanocomposite system possessed good capability for providing the fuel cell with hydrogen flow at an average rate of 150 ml/min.

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Recently, transition metal oxides have been evidenced to be superior catalysts for improving the hydrogen desorption/absorption performance of MgH2. In this paper, Mn3O4 nanoparticles with a uniform size of around 10 nm were synthesized by a facile chemical method and then introduced to modify the hydrogen storage properties of MgH2. With the addition of 10 wt% Mn3O4 nanoparticles, the MgH2-Mn3O4 composite started to release hydrogen at 200 °C and approximately 6.8 wt% H2 could be released within 8 min at 300 °C. For absorption, the completely dehydrogenated sample took up 5.0 wt% H2 within 10 min under 3 MPa hydrogen even at 100 °C. Compared with pristine MgH2, the activation energy value of absorption for the MgH2 + 10 wt% Mn3O4 composite decreased from 72.5 ± 2.7 to 34.4 ± 0.9 kJ mol-1. The catalytic mechanism of Mn3O4 was also explored and discussed with solid evidence from X-ray diffraction (XRD), Transmission Electron Microscope (TEM) and Energy Dispersive X-ray Spectroscopy (EDS) studies. Density functional theory calculations revealed that the Mg-H bonds were elongated and weakened with the doping of Mn3O4. In addition, a cycling test showed that the hydrogen storage capacity and reaction kinetics of MgH2-Mn3O4 could be favourably preserved in 20 cycles, indicative of promising applications as a solid-state hydrogen storage material in a future hydrogen society. This journal is © The Royal Society of Chemistry.

Recently, transition metal oxides have been evidenced to be superior catalysts for improving the hydrogen desorption/absorption performance of MgH2. For absorption, the completely dehydrogenated sample took up 5.0 wt% H2 within 10 min under 3 MPa hydrogen even at 100 °C.

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Due to its affordable price, abundance, high storage capacity, low recycling coast, and easy processing, Mg metal is considered as a promising hydrogen storage material. However, the poor de/rehydrogenation kinetics and strong stability of MgH2 must be improved before proposing this material for applications. Doping MgH2 powders with one or more catalytic agents is one common approach leading to obvious improving on the behavior of MgH2. The present study was undertaken to investigate the effect of doping MgH2 with 7 wt% of amorphous(a)-LaNi3 nanopowders on hydrogenation/dehydrogenation behavior of the metal hydride powders. The results have shown that rod milling MgH2 with a-LaNi3 abrasive nanopowders led to disintegrate microscale-MgH2 powders to nanolevel. The final nanocomposite product obtained after 50 h–100 h of rod milling revealed superior hydrogenation kinetics, indexed by short time (8 min) required to absorb 6 wt% of H2 at 200◦C/10 bar. At 225◦C/200 mbar, nanocomposite powders revealed outstanding dehydrogenation kinetics, characterized by very short time (2 min) needed to release 6 wt% of H2. This new tailored solid-hydrogen storage system experienced long cycle-life-time (2000 h) at 225◦C without obeying to sever degradation on its kinetics and/or storage capacity. © 2019 by the authors.

However, the poor de/rehydrogenation kinetics and strong stability of MgH2 must be improved before proposing this material for applications. At 225◦C/200 mbar, nanocomposite powders revealed outstanding dehydrogenation kinetics, characterized by very short time (2 min) needed to release 6 wt% of H2.

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Lithium alanate (LiAlH4) is of particular interest as one of the most promising candidates for solid-state hydrogen storage. Unfortunately, high dehydrogenation temperatures and relatively slow kinetics limit its practical applications. Herein, 3D flower-like nanocrystalline Ni/C, composed of highly dispersed Ni nanoparticles and interlaced carbon flakes, was synthesized in situ. The as-synthesized nanocrystalline Ni/C significantly decreased the dehydrogenation temperature and dramatically improved the dehydrogenation kinetics of LiAlH4. It was found that the LiAlH4 sample with 10 wt % Ni/C (LiAlH4-10 wt %Ni/C) began hydrogen desorption at approximately 48 °C, which is very close to ambient temperature. Approximately 6.3 wt % H2 was released from LiAlH4-10 wt %Ni/C within 60 min at 140 °C, whereas pristine LiAlH4 only released 0.52 wt % H2 under identical conditions. More importantly, the dehydrogenated products can partially rehydrogenate at 300 °C under 4 MPa H2. The synergetic effect of the flower-like carbon substrate and Ni active species contributes to the significantly reduced dehydrogenation temperatures and improved kinetics. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Unfortunately, high dehydrogenation temperatures and relatively slow kinetics limit its practical applications. Herein, 3D flower-like nanocrystalline Ni/C, composed of highly dispersed Ni nanoparticles and interlaced carbon flakes, was synthesized in situ.

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Hydrogen energy is a highly efficient and renewable energy carrier. The rapid and sophisticated development of nanotechnologies has promoted the transition of hydrogen storage systems from gaseous/liquid to solid-state. In order to clarify the intrinsic relationship between structure and performance, and to understand the hydrogen absorption and desorption mechanism of materials, electron microscopy (EM) can effectively help us obtain a series of information such as particle size, phase and composition determination, morphology and structure of the materials at nanoscale. The most recent progress of advanced EM techniques applied in solid-state hydrogen storage materials are summarized, which should also inspire future research on energy storage related materials. © 2020 Hydrogen Energy Publications LLC

The rapid and sophisticated development of nanotechnologies has promoted the transition of hydrogen storage systems from gaseous/liquid to solid-state. The most recent progress of advanced EM techniques applied in solid-state hydrogen storage materials are summarized, which should also inspire future research on energy storage related materials.

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Magnesium hydride and selected magnesium-based ternary hydride (Mg2FeH6, Mg2NiH4, and Mg2CoH5) syntheses and modification methods, as well as the properties of the obtained materials, which are modified mostly by mechanical synthesis or milling, are reviewed in this work. The roles of selected additives (oxides, halides, and intermetallics), nanostructurization, polymorphic transformations, and cyclic stability are described. Despite the many years of investigations related to these hydrides and the significant number of different additives used, there are still many unknown factors that affect their hydrogen storage properties, reaction yield, and stability. The described compounds seem to be extremely interesting from a theoretical point of view. However, their practical application still remains debatable. © 2020 by the authors.

Despite the many years of investigations related to these hydrides and the significant number of different additives used, there are still many unknown factors that affect their hydrogen storage properties, reaction yield, and stability. The described compounds seem to be extremely interesting from a theoretical point of view.

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We have investigated the structure and hydrogen storage properties of a series of quaternary and quintary high-entropy alloys related to the ternary system TiVNb with powder X-ray diffraction (PXD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and manometric measurements in a Sieverts apparatus. The alloys have body-centred cubic (bcc) crystal structures and form face-centred cubic (fcc) metal hydrides with hydrogen-to-metal ratios close to 2 by hydrogenation. The onset temperature for hydrogen desorption, Tonset, decreases linearly with the valence-electron concentration, VEC. Moreover, the volumetric expansion per metal atom from the bcc alloys to the fcc hydrides, [(V/Z)fcc−(V/Z)bcc]/(V/Z)bcc, increases linearly with the VEC. Therefore, it seems that a larger expansion of the lattice destabilizes the metal hydrides and that this effect can be tuned by altering the VEC. Kissinger analyses performed on the DSC measurements indicate that the destabilization is a thermodynamic rather than kinetic effect. Based upon these insights we have identified TiVCrNbH8 as a material with suitable thermodynamics for hydrogen storage in the solid state. This HEA-based hydride has a reversible hydrogen storage capacity of 1.96 wt% H at room temperature and moderate H2-pressures. Moreover, it is not dependent on any elaborate activation procedure to absorb hydrogen. © 2019 Acta Materialia Inc.

Based upon these insights we have identified TiVCrNbH8 as a material with suitable thermodynamics for hydrogen storage in the solid state. This HEA-based hydride has a reversible hydrogen storage capacity of 1.96 wt% H at room temperature and moderate H2-pressures.

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Polygeneration Microgrids (PMG) are smart energy systems which can be configured for decentralised multiple outputs in the form of electricity, heat, cold, fuel (hydrogen) and drinking water. This paper presents an analysis of a stand-alone PMG, which caters to electrical, thermal and hydrogen loads. The stand-alone PMG consisting of solar photovoltaic field, fuel cell, solid state hydrogen storage and electrolyzer is modelled using commercial software HOMER. An hourly simulation is conducted to analyse its annual performance. A case study is carried out for a typical Indian village of about 50 households needing electrical energy of 100 kWh/day. The by-products of the optimized stand-alone PMG i.e., thermal energy and hydrogen, are quantified. © 2020 Elsevier Ltd

Polygeneration Microgrids (PMG) are smart energy systems which can be configured for decentralised multiple outputs in the form of electricity, heat, cold, fuel (hydrogen) and drinking water. The stand-alone PMG consisting of solar photovoltaic field, fuel cell, solid state hydrogen storage and electrolyzer is modelled using commercial software HOMER.

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The rapid and extensive development of advanced nanostructures and nanotechnologies has driven a correspondingly rapid growth of research that presents enormous potential for fulfilling the practical requirements of solid state hydrogen storage applications. This article reviews the most recent progress in the development of nanostructured materials for hydrogen storage technology, demonstrating that nanostructures provide a pronounced benefit to applications involving molecular hydrogen storage, chemical hydrogen storage, and as supports for the nanoconfinement of various hydrides. To further optimize hydrogen storage performance, we emphasize the desirability of exploring and developing nanoporous materials with ultrahigh surface areas and the advantageous incorporation of metals and functionalities, nanostructured hydrides with excellent mechanic stabilities and rigid main construction, and nanostructured supports comprised of lightweight components and enhanced hydride loading capacities. In addition to highlighting the conspicuous advantages of nanostructured materials in the field of hydrogen storage, we also discuss the remaining challenges and the directions of emerging research for these materials. © 2017 Elsevier Ltd

The rapid and extensive development of advanced nanostructures and nanotechnologies has driven a correspondingly rapid growth of research that presents enormous potential for fulfilling the practical requirements of solid state hydrogen storage applications. This article reviews the most recent progress in the development of nanostructured materials for hydrogen storage technology, demonstrating that nanostructures provide a pronounced benefit to applications involving molecular hydrogen storage, chemical hydrogen storage, and as supports for the nanoconfinement of various hydrides.

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This review summarizes the results of the studies of structural and absorption characteristics of thin-film (V, Ti)Nx-Hy hydrogen storage devices that have been conducted at the National Science Center "Kharkov Institute of Physics and Technology" in the last 10 years. It sets out analyzing the basic principles for producing the porous nano-crystalline thin films using the Ion-Beam Assisted Deposition (IBAD) technique. The detailed analysis of electron microscopic investigation of the film structure at all growth stages (from 5 nm to 1 μm) is provided. It is shown how the bombardment with gas ions during the film deposition contributes to a formation of intergranular nanopores. The size of nanopores and their distribution were determined by means of neutron spectroscopy analysis. Using the nuclear-physical methods, the total volume of intergranular pores was measured and it was shown that, depending on the parameters of the IBAD process, the porosity can vary from 10 to 27 vol. %. It was noted that nuclear physics methods are also relevant for determining the hydrogen amount absorbed by thin films. The review contains the results of research regarding the influence of the film thickness, the presence of a protective nickel coating, and the hydrogen saturation technique on the gravimetric capacity of the films. Investigated nanoporous (V, Ti)Nx-Hy thin films can absorb up to 8 wt. % of hydrogen, and hydrogen release occurs in the temperature range from 50 to 350°C. Based on the results of the studies, it is substantiated why the transition from simple vanadium and titanium hydrides to complex ones leads to a significant improvement both of their gravimetric capacity and thermodynamic and kinetic characteristics. © 2018 by Nova Science Publishers, Inc. All rights reserved.

It was noted that nuclear physics methods are also relevant for determining the hydrogen amount absorbed by thin films. Investigated nanoporous (V, Ti)Nx-Hy thin films can absorb up to 8 wt.

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In the present study, a cylindrical solid state hydrogen storage device embedded with finned heat exchanger is numerically investigated. The finned heat exchanger consists of two ‘U’ shaped tube and circular fins brazed on the periphery of the tubes. 1 kg of LaNi5 alloy is filled inside the device and 80 g of copper flakes is evenly distributed in between the fins to increase the overall thermal conductivity of the metal hydride. Water is used as heat transfer fluid. Absorption performance of the storage device is investigated at constant hydrogen supply pressure of 15 bar and cooling fluid temperature and velocity of 298 K and 1 m/s respectively. At these operating conditions, the required charging time is found to be around 610 s for a storage capacity of 12 g (1.2 wt%). The study is extended to examine the influence of different heat exchanger configurations based on number of fins, thickness of the fins, diameter of tubes, holes in fins, amount of copper flakes etc. An analysis for the same weight of the heat exchanger assembly has also been carried out by changing the number of fins at different thickness and pitch. © 2017 Hydrogen Energy Publications LLC

In the present study, a cylindrical solid state hydrogen storage device embedded with finned heat exchanger is numerically investigated. At these operating conditions, the required charging time is found to be around 610 s for a storage capacity of 12 g (1.2 wt%).

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With advantages of high hydrogen capacity, excellent reversibility, and low cost, magnesium hydride (MgH2) has been considered as one of the most promising candidates for solid-state hydrogen storage. However, the practical use of MgH2 as a hydrogen storage medium still needs to overcome great barriers both in the thermodynamics and kinetics. In this respect, nanotechnology plays an important role. Employing appropriate nanocatalysts for the hydrogen sorption and/or reducing the particle size of MgH2 to nanoscale have been demonstrated to be effective strategies. In this review, we present a detailed survey on the recent advances in nanocatalysts and nanostructuring for high-performance MgH2. First, we introduce various categories of nanocatalysts, especially including metals and their compounds, focusing on their effects on hydrogen sorption performance of MgH2. Then nanostructuring methods for the preparation of small-sized freestanding Mg/MgH2 are discussed, and typical works in nanoconfinement of MgH2 are revisited as a nanostructuring methodology. Finally, we analyze the remaining issues and challenges and propose the prospects of research and development in MgH2 as hydrogen storage materials in the future. © 2019 Elsevier Ltd

With advantages of high hydrogen capacity, excellent reversibility, and low cost, magnesium hydride (MgH2) has been considered as one of the most promising candidates for solid-state hydrogen storage. Then nanostructuring methods for the preparation of small-sized freestanding Mg/MgH2 are discussed, and typical works in nanoconfinement of MgH2 are revisited as a nanostructuring methodology.

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Solid-state hydrogen storage materials undergo complex phase transformations in which kinetics are often limited by hydrogen diffusion that significantly changes during hydrogen uptake and release. Here we perform robust statistically-averaged molecular dynamics simulations to obtain a well-converged analytical expression for hydrogen diffusivity in bulk palladium that is valid throughout all stages of the reaction. Our studies confirm the experimentally observed dependence of the diffusivity on concentration and temperature and elucidate the underlying physics. Whereas at low hydrogen concentrations, a single dilute hopping barrier dominates, at high hydrogen concentrations, diffusion exhibits multiple hopping barriers corresponding to hydrogen-rich and hydrogen-poor local environments. © 2018

Here we perform robust statistically-averaged molecular dynamics simulations to obtain a well-converged analytical expression for hydrogen diffusivity in bulk palladium that is valid throughout all stages of the reaction. Whereas at low hydrogen concentrations, a single dilute hopping barrier dominates, at high hydrogen concentrations, diffusion exhibits multiple hopping barriers corresponding to hydrogen-rich and hydrogen-poor local environments.

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The high dehydrogenation temperature of magnesium hydride MgH2 is still the main obstacle to its practical application as a solid-state hydrogen storage medium. Using experimental and first-principles calculations approaches, we, for the first time, investigate the catalytic effect and mechanism of nickel phthalocyanine on the dehydrogenation properties of MgH2. The results display that a small amount of nickel phthalocyanine can promote MgH2 dehydrogenation at significantly decreased temperatures by more than 90 °C relative to milled pristine or graphene-added MgH2 system. However, the agglomeration of MgH2 particles is not evidently alleviated through nickel phthalocyanine addition. When MgH2 is milled with graphene firstly and then the obtained mixture is further milled with nickel phthalocyanine, the dehydrogenation properties and agglomeration of MgH2 particles can be synergistically improved to some extent. The first-principles calculations of dehydrogenation enthalpy and binding energy account for the experimental differences in catalysis and aggregation-resistance abilities of nickel phthalocyanine and graphene on MgH2 particles. Notably, the NiN4-inserted graphene is predicted to be an ideal additive for MgH2, which combines the synergetic catalysis-confinement effect of nickel phthalocyanine and graphene on MgH2 particles. Analysis of electronic structures reveals that the excellent catalytic effect of nickel phthalocyanine on MgH2 can be ascribed to the more electron transfer between nickel phthalocyanine and MgH2, which induces the significantly weakened bond strength of Mg[sbnd]H and decreased dehydrogenation enthalpy of MgH2. © 2017 Hydrogen Energy Publications LLC

The results display that a small amount of nickel phthalocyanine can promote MgH2 dehydrogenation at significantly decreased temperatures by more than 90 °C relative to milled pristine or graphene-added MgH2 system. When MgH2 is milled with graphene firstly and then the obtained mixture is further milled with nickel phthalocyanine, the dehydrogenation properties and agglomeration of MgH2 particles can be synergistically improved to some extent.

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High-pressure torsion (HPT) is widely used as a severe plastic deformation technique to create ultrafine-grained structures with promising mechanical and functional properties. Since 2007, the method has been employed to enhance the hydrogenation kinetics in different Mg-based hydrogen storage materials. Recent studies showed that the method is effective not only for increasing the hydrogenation kinetics but also for improving the hydrogenation activity, for enhancing the air resistivity and more importantly for synthesizing new nanostructured hydrogen storage materials with high densities of lattice defects. This manuscript reviews some major findings on the impact of HPT process on the hydrogen storage performance of different titanium-based and magnesium-based materials. © 2018 The Author(s). Published by National Institute for Materials Science in partnership with Taylor & Francis.

High-pressure torsion (HPT) is widely used as a severe plastic deformation technique to create ultrafine-grained structures with promising mechanical and functional properties. Published by National Institute for Materials Science in partnership with Taylor & Francis.

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Currently, hydrogen storage research is generally on-board-application oriented. However, the scenario of grid-scale hydrogen energy storage is remarkably different fromon-board application, thus leading to diversity of performance requirements for hydrogen storage. In this paper, technical indicators of solid-state hydrogen storage systems and hydrogen storage materials for grid-scale hydrogen energy storage were studied. Firstly, performance requirements of hydrogen uptake and release for the hydrogen storage system were obtained by analyzing technical characteristics of electrolysis system and fuel cell system. Then, the technical targets of the solid-state hydrogen storage system and hydrogen storage materials for grid-scale application were put forwards, taking into account research and development status of hydrogen storage technology. The technical targets will guide research and development of solid-state hydrogen storage technology and materials for grid-scale applicationin the future. © 2017, Power System Technology Press. All right reserved.

However, the scenario of grid-scale hydrogen energy storage is remarkably different fromon-board application, thus leading to diversity of performance requirements for hydrogen storage. The technical targets will guide research and development of solid-state hydrogen storage technology and materials for grid-scale applicationin the future.

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The absorption and desorption performances of a solid state (metal hydride) hydrogen storage device with a finned tube heat exchanger are experimentally investigated. The heat exchanger design consists of two “U” shaped cooling tubes and perforated annular copper fins. Copper flakes are also inserted in between the fins to increase the overall effective thermal conductivity of the metal hydride bed. Experiments are performed on the storage device containing 1 kg of hydriding alloy LaNi5, at various hydrogen supply pressures. Water is used as the heat transfer fluid. The performance of the storage device is investigated for different operating parameters such as hydrogen supply pressure, cooling fluid temperature and heating fluid temperature. The shortest charging time found is 490 s for the absorption capacity of 1.2 wt% at a supply pressure of 15 bar and cooling fluid temperature and velocity of 288 K and 1 m/s respectively. The effect of copper flakes on absorption performance is also investigated and compared with a similar storage device without copper flakes. © 2017 Hydrogen Energy Publications LLC

The heat exchanger design consists of two “U” shaped cooling tubes and perforated annular copper fins. Experiments are performed on the storage device containing 1 kg of hydriding alloy LaNi5, at various hydrogen supply pressures.

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Solid-state hydrogen storage in metal hydrides offers highest volumetric energy storage densities and low working gas pressures at the same time. Recently developed metal hydride composites (MHC) consist of a hydride-forming metal alloy and a secondary phase, typically graphite, to realize form-stable composites and short loading and unloading times (<5 min). Hydride formation causes a volume expansion of the storage material. Thus, it is mandatory to characterize this behavior for the sake of system safety. This work focuses on the in-operando characterization of the volume expansion of MHC that could trigger mechanical stresses acting on the walls and internal assemblies of the storage container. MHC with different metal particle shapes (flakes and powder) were studied. In-operando neutron imaging of axially freely expanding MHC was applied to analyze the time-resolved and spatial concentration of hydrogen, reaction fronts and the evolution of volume expansion and stability of the MHC. Stress measurements revealed that stresses of up to 330% of the respective operating gas pressure occur for confined MHC. Both techniques combined deliver crucial information and implications for the design of safe (according to ISO 16111), efficient and dynamic metal hydride storage systems. © 2018 Elsevier B.V.

Thus, it is mandatory to characterize this behavior for the sake of system safety. MHC with different metal particle shapes (flakes and powder) were studied.

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Novel nano biomass (NBM) was synthesized using a general and simple synthetic approach. In this process, the walnut shell is used as a green carbon source. According to the transmission electron microscopy and dynamic light scattering results, the average particle size of the produced activated carbon was 2.25 nm. The surface area of the NBM was around 420.5 m2/g totally. High pore volume, high internal surface area, lightweight as well as easy availability are some features that attract research interests on activated carbon as a solid-state hydrogen storage medium. Nano biomass was deposited directly on a copper substrate by the slurry-coating method. The electrochemical properties of nano biomass were investigated in a three-electrode electrolytic cell with 6 M KOH as the electrolyte by galvanostatic charging and discharging. Several parameters such as the impact of the number of charge and discharge cycles and discharge time are studied. Different experimental results show that Cu-NBM has 1596 mAh/g discharge capacity (corresponding to a hydrogen storage capacity of 5.66 wt%) after 16 cycles at room temperature and atmospheric conditions. Due to porosity of NBM particles, the nano biomass showed reversible hydrogen storage capacities that were better than those of previously reported porous carbons. © 2019 Hydrogen Energy Publications LLC

Novel nano biomass (NBM) was synthesized using a general and simple synthetic approach. Nano biomass was deposited directly on a copper substrate by the slurry-coating method.

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LiBH4 is of particular interest as one of the most promising materials for solid-state hydrogen storage. Herein, LiBH4 is confined into a novel two-dimensional layered Ti3C2 MXene through a facile impregnation method for the first time to improve its hydrogen storage performance. The initial desorption temperature of LiBH4 is significantly reduced, and the de-/rehydrogenation kinetics are remarkably enhanced. It is found that the initial desorption temperature of LiBH4@2Ti3C2 hybrid decreases to 172.6 °C and releases 9.6 wt % hydrogen at 380 °C within 1 h, whereas pristine LiBH4 only releases 3.2 wt % hydrogen under identical conditions. More importantly, the dehydrogenated products can partially rehydrogenate at 300 °C and under 95 bar H2. The nanoconfined effect caused by unique layered structure of Ti3C2 can hinder the particles growth and agglomeration of LiBH4. Meanwhile, Ti3C2 could possess superior effect to destabilize LiBH4. The synergetic effect of destabilization and nanoconfinement contributes to the remarkably lowered desorption temperature and improved de-/rehydrogenation kinetics. © 2018 American Chemical Society.

It is found that the initial desorption temperature of LiBH4@2Ti3C2 hybrid decreases to 172.6 °C and releases 9.6 wt % hydrogen at 380 °C within 1 h, whereas pristine LiBH4 only releases 3.2 wt % hydrogen under identical conditions. More importantly, the dehydrogenated products can partially rehydrogenate at 300 °C and under 95 bar H2.

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Low temperature formation of Mg2FeH6 is demonstrated by hydrogenation of Mg-Fe elemental powder mixture at a temperature as low as 350 °C which is lower than the conventional process temperature, 500 °C. To enable the low temperature synthesis, the powder mixture of Mg and Fe has been prepared by high energy ball milling using different process control agents (PCAs). A systematic study on the ball milling and hydrogenation conditions has been carried out to maximize the yield of the ternary line compound. The hydrogenation conditions together with the particle size of the starting materials turn out to play a significant role in the hydrogenation kinetics of the system. An optimized condition has demonstrated a significant hydrogenation as well as a robust cycling ability at low temperature which suggests the strong potential of the process for practical applications. © 2017 Elsevier Ltd

To enable the low temperature synthesis, the powder mixture of Mg and Fe has been prepared by high energy ball milling using different process control agents (PCAs). An optimized condition has demonstrated a significant hydrogenation as well as a robust cycling ability at low temperature which suggests the strong potential of the process for practical applications.

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In this study, the nano-mixture of LiBH4 + MgH2 is prepared by ball milling (BM) of 1 mol MgH2 with in-situ aerosol-spraying (AS) of 1 mol of LiBH4 (called BMAS). It is shown, for the first time, that Mg(BH4)2 can be formed via the reaction between MgH2 and LiBH4 through the BMAS process and it contributes to H2 release at temperature ≤265 °C. Three parallel H2 release mechanisms have been identified from the BMAS powder. These include (i) H2 release from the decomposition of nano-LiBH4 and then Li2B12H12 decomposition product reacts with nano-MgH2 to release H2, (ii) H2 release from the decomposition of nano-Mg(BH4)2, and (iii) H2 release from the decomposition of nano-MgH2. Together, these three mechanisms result in 4.11 wt% H2 release in the solid-state at temperature ≤265 °C, which is among the highest quantities ever reported for LiBH4 + MgH2 mixtures to date. Furthermore, the H2 release temperature for each mechanism described above is lower than the corresponding temperature reported using other synthesis methods. In addition, the predicted property of a small amount of the Fe3B phase in the BMAS powder in absorbing more H2 than releasing is confirmed experimentally for the first time in this study. All these enhancements are achieved in the solid-state without any catalyst, which highlights the efficacy of mechanical activation and nanoengineering as well as the future opportunity to further improve the reversible hydrogen storage properties of LiBH4 + MgH2 in solid-state. © 2019

Three parallel H2 release mechanisms have been identified from the BMAS powder. Together, these three mechanisms result in 4.11 wt% H2 release in the solid-state at temperature ≤265 °C, which is among the highest quantities ever reported for LiBH4 + MgH2 mixtures to date.

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As important as the production of CO2-free energy is, so is the motivation to develop efficient storage of renewable energies for mobile and stationary applications. There is no doubt that metal hydrides continue to attract the overall materials science community, and it is not only restrained to a specialized hydrogen field. This is mainly the case when it is the matter of coupled technologies with other systems such as fuel cells, heat management, and batteries. Hydrogen is considered an energy carrier and its chemical energy can be converted into electricity through a chemical reaction with oxygen from a fuel cell. Therefore, coupling energy storage systems with renewable energy sources through an electrolyzer, which can transform electric energy into hydrogen chemical energy, is considered a high sustainable process of production and exploitation of renewable energies. Integrated systems are constituted by a metal hydride tank and a PEM fuel cell, in which the waste heat generated in the fuel cell is used to supply the necessary heat required for desorption of hydrogen from the tank. The field of application of the integrated power system is in combination with renewable sources: The hydrogen can be produced by electrolysis of water using the energy from a renewable source (e.g., photovoltaic); it is then stored and converted into electric energy by the proposed integrated power system, that allows energy storage in the form of hydrogen and its reuse when the renewable source is not available, for example, at night if solar power is exploited. The developed power system could replace batteries and could be applied in the case of a production plant not connected to the power grid, such as in remote areas. As an example, an integrated power system, showing a total energy production of 4.8 kW h, over more than 6 h of working activity, is reported in ref 4. In the SSH2S (Fuel Cell Coupled Solid-State Hydrogen Storage Tank) project, a solid-state hydrogen storage tank based on complex hydrides has been developed and it was fully integrated with a High-Temperature Proton Exchange Membrane (HT-PEM) fuel cell stack. The hydrogen storage tank was designed to feed a 1 kW HT-PEM stack for 2 h to be used for an Auxiliary Power Unit (APU).61 With respect to batteries, hydrides can be utilized as anodes with high capacity (e.g., 2 Ahg-1 for MgH2). A lot of effort has been expended to improve the cyclability, and significant results have been reached in a solid-state battery with LiBH4 solid electrolyte. Demonstration of high-energy density fuel cells with suitable cathodes will be the challenge of upcoming research studies.62,63 As mentioned for the beneficial contribution of electrodes, solid-state electrolytes based on borohydrides are a typical example that the battery community is now taking seriously along with the popular garnet-type solid electrolytes.64,65 It has been demonstrated that the ionic conductivity is a prerequisite for application in batteries, but unfortunately it is not win; in fact, other important issues need to be tackled, such as chemical compatibility, interfaces, heterogeneity, and mechanical properties, so important for the cell engineering and design, in addition to the structural and volumetric changes during cycling. At first, borohydrides meet some of these criteria regarding conductivity and ductility, (thermo)chemistry, and low-density materials. Future research might be directed to the understanding and assessment of interfaces and physical and mechanical properties of the selected solid-electrolyte and electrodes. The specificity of the application may become a determining aspect in the selection of the suitable configuration. Substantial research efforts are being conducted to study new approaches toward the utilization of borohydrides and closo-type complex hydrides in composites.66,67 Thanks to their ductility and ionic conductivity, borohydrides can be also employed as additives for binder-free solid-state batteries. Since the demonstration of LiBH4 thin film growth,68 this could be considered for mitigating the formation of dendrite and oxidation layers on the surface of lithium metal. Another direction is focused on the development of Mg2+ conducting solid electrolytes for application in Mg batteries, which offer higher volumetric capacity compared to lithium at low cost. At present, the technology can be only possible at high-T owing to the low ionic conductivity and Mg2+-ion mobility.69 In addition, metal hydrides can be utilized as optical hydrogen sensors for the detection of hydrogen at low pressure levels according to changes in the optical properties, which is a step forward regarding the increase of the safety for advanced hydrogenbased systems. Lastly, compared to the traditional conferences for hydrogen community (MH, E-MRS, Gordon, etc.) there no doubt that IRSEC is a particular place to meet scientists and experts in the African context undergoing full energy boom. The eighth edition of IRSEC will continue the tradition of drawing the best scientists in the field of sustainable energy, which will be held in Tangier (Morocco), November 25-28, 2020. We thank the local organizers and students, the participants, and the speakers of this Special Session for their excellent contributions. © 2020 American Chemical Society. All rights reserved.

Another direction is focused on the development of Mg2+ conducting solid electrolytes for application in Mg batteries, which offer higher volumetric capacity compared to lithium at low cost. there no doubt that IRSEC is a particular place to meet scientists and experts in the African context undergoing full energy boom.

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In addition to serving as an important energy carrier, hydrogen storage material also has the potential to be used as an effective solid reducing agent. This paper is concerned with the application of MgH2/MoS2 hydrogen storage materials to thiophene desulfurization through catalytic transfer hydrogenation. The hydrogen content of the as-prepared MgH2/MoS2 composites is determined to be 6.15 wt% with a dehydrogenation peak temperature of 402 °C. Taking MgH2 as hydrogen donor, thiophene hydrodesulfurization has taken place at atmospheric pressure and at the temperature lower than the onset desorption temperature, indicating that a coupling effect occurs between MgH2 decomposition and thiophene hydrogenation. It is further revealed that sulfur removal in thiophene under the studied condition preferentially proceeds via direct desulfurization (DDS) route. Our density functional theory (DFT) calculations manifest that energy barriers of the minimum energy path for thiophene hydrodesulfurization are all <1.35 eV. This exploratory case study demonstrates the feasibility of catalytic transfer hydrogenation using solid-state hydrogen storage materials. © 2018 Elsevier Ltd

This paper is concerned with the application of MgH2/MoS2 hydrogen storage materials to thiophene desulfurization through catalytic transfer hydrogenation. It is further revealed that sulfur removal in thiophene under the studied condition preferentially proceeds via direct desulfurization (DDS) route.

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Absorption of hydrogen gas inside the metal hydride (MH)-based hydrogen storage system generates significant amount of heat. This heat must be removed rapidly to improve the performance of the system which can be accomplished by embedding a heat exchanger inside the MH bed. In this article, a tubular shape MH system, equipped with a heat exchanger consisting of copper tube and pin fin is presented. A detailed 3D mathematical model is developed using COMSOL Multiphysics 4.3b for the numerical study of absorption and desorption processes inside the storage system. Impact of various operating and geometric parameters on the charging time of the storage system has been examined. It is observed that these geometric and operating parameters influence the charging time of the storage system. In the last, the impact of heat exchanger material on the performance of the storage system is explored. It is found that aluminum made heat exchanger is the best for the storage systems. The absorption process is accomplished in 1152 s at the operating parameters of 15 bar, 298 K, and 6.75 lit/min. This numerical work suggests that the efficient design of storage system is very important for rapid absorption and desorption of hydrogen. © 2018, © 2018 Taylor & Francis Group, LLC.

In this article, a tubular shape MH system, equipped with a heat exchanger consisting of copper tube and pin fin is presented. A detailed 3D mathematical model is developed using COMSOL Multiphysics 4.3b for the numerical study of absorption and desorption processes inside the storage system.

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Solid-state hydrogen storage technology currently suffers from issues such as inadequate storage capacity, and instability, leading to low performances. Here we show a record of above 2000 mAh.g−1 (∼7.8 wt% H) of discharge capacity of a binary metal oxides Ce0.75Zr0.25O2 nanopowders. The yellowish Ce0.75Zr0.25O2 nanopowders have been synthesized via a sol-gel method under thermal treatment of the molecular precursors of the, (NH4)2Ce(NO3)6 and C16H40O4Zr. The crystal structure and morphology evolution can be described by the cubic and highly pure structure and homogeneous nanoscales formation of Ce0.75Zr0.25O2, ranging from 35 to 60 nm. The formation of the Ce0.75Zr0.25O2 nanoparticles distinctly matches with the spectroscopy results. The activation energy (Ea) was calculated from the output of a reduction thermal programming profile at about 177 kJ mol−1 using Kissinger equation. Our work will promote the development of low-cost solid-state semiconductors based on transition metals, as a host for hydrogen sorption. © 2019 Elsevier B.V.

The activation energy (Ea) was calculated from the output of a reduction thermal programming profile at about 177 kJ mol−1 using Kissinger equation. Our work will promote the development of low-cost solid-state semiconductors based on transition metals, as a host for hydrogen sorption.

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Sodium borohydride (NaBH4) is a promising solid-state hydrogen storage material because of its low toxicity, high environmental stability and release of high-purity hydrogen. Nevertheless, the practical application of NaBH4 is still hampered by its high desorption temperature and slow hydrogen exchange kinetics. Using experimental and first-principles calculations approaches, the dehydrogenation properties and modifying mechanisms of NaBH4+10 wt%graphene composite acquired by ball-milling are systematically investigated in this work. The results show that the graphene plays a cooperative catalysis–confinement effect on NaBH4. X-ray diffraction analysis displays that no new phases formed due to the mutual inertia between NaBH4 and graphene during ball-milling. Scanning electron microscopy and transmission electron microscopy observations show that the NaBH4 particles are significantly refined after graphene addition, which effectively restrains the agglomeration of NaBH4 particles. Thermogravimetry testing and mass spectrometry testing indicate that the onset dehydrogenation temperature of the NaBH4+10 wt%graphene composite is decreased by about 114 °C relative to the milled pristine NaBH4. First-principles calculations reveal that the enhanced dehydrogenation properties of NaBH4 after graphene addition should be ascribed to the reduced dehydrogenation enthalpy of NaBH4 and strong binding energy between NaBH4 and graphene as well as the electron transfer from NaBH4 to graphene. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

Nevertheless, the practical application of NaBH4 is still hampered by its high desorption temperature and slow hydrogen exchange kinetics. X-ray diffraction analysis displays that no new phases formed due to the mutual inertia between NaBH4 and graphene during ball-milling.

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The hydrogen storage properties of 6Mg(NH2)2[sbnd]9LiH-x(LiBH4)(x = 0, 0.5, 1, 2)system and the role of LiBH4 on the kinetic behaviour and the dehydrogenation/hydrogenation reaction mechanism were herein systematically investigated. Among the studied compositions, 6Mg(NH2)2[sbnd]9LiH[sbnd]2LiBH4 showed the best hydrogen storage properties. The presence of 2 mol of LiBH4 improved the thermal behaviour of the 6Mg(NH2)2[sbnd]9LiH by lowering the dehydrogenation peak temperature nearly 25 °C and by reducing the apparent dehydrogenation activation energy of about 40 kJ/mol. Furthermore, this material exhibited fast dehydrogenation (10 min)and hydrogenation kinetics (3 min)and excellent cycling stability with a reversible hydrogen capacity of 3.5 wt % at isothermal 180 °C. Investigations on the reaction pathway indicated that the observed superior kinetic behaviour likely related to the formation of Li4(BH4)(NH2)3. Studies on the rate-limiting steps hinted that the sluggish kinetic behaviour of the 6Mg(NH2)2[sbnd]9LiH pristine material are attributed to an interface-controlled mechanism. On the contrary, LiBH4-containing samples show a diffusion-controlled mechanism. During the first dehydrogenation reaction, the possible formation of Li4(BH4)(NH2)3 accelerates the reaction rates at the interface. Upon hydrogenation, this ‘liquid like’ of Li4(BH4)(NH2)3 phase assists the diffusion of small ions into the interfaces of the amide-hydride matrix. © 2019 Hydrogen Energy Publications LLC

Furthermore, this material exhibited fast dehydrogenation (10 min)and hydrogenation kinetics (3 min)and excellent cycling stability with a reversible hydrogen capacity of 3.5 wt % at isothermal 180 °C. On the contrary, LiBH4-containing samples show a diffusion-controlled mechanism.

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The effective storage of H2 gas represents one of the major challenges in the wide spread adoption of hydrogen powered fuel cells for light vehicle transportation. Here, we investigate the merits of chemically hydrogenated graphene (graphane) as a means to store high-density hydrogen fuel for on demand delivery. In order to evaluate hydrogen storage at the macroscale, 75 g of hydrogenated graphene was synthesized using a scaled up Birch reduction, representing the largest reported synthesis of this material to date. Covalent hydrogenation of the material was characterized via Raman spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). We go on to demonstrate the controlled release of H2 gas from the bulk material using a sealed pressure reactor heated to 600 °C, identifying a bulk hydrogen storage capacity of 3.2 wt%. Additionally, we demonstrate for the first time, the successful operation of a hydrogen fuel cell using chemically hydrogenated graphene as a power source. This work demonstrates the utility of chemically hydrogenated graphene as a high-density hydrogen storage medium, and will be useful in the design of prototype hydrogen storage systems moving forward. © 2019

Here, we investigate the merits of chemically hydrogenated graphene (graphane) as a means to store high-density hydrogen fuel for on demand delivery. Covalent hydrogenation of the material was characterized via Raman spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA).

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Reaction kinetic behaviour and cycling stability of the 2LiBH4-MgH2 reactive hydride composite (Li-RHC) are experimentally determined and analysed as a basis for the design and development of hydrogen storage tanks. In addition to the determination and discussion about the properties; different measurement methods are applied and compared. The activation energies for both hydrogenation and dehydrogenation are determined by the Kissinger method and via the fitting of solid-state reaction kinetic models to isothermal volumetric measurements. Furthermore, the hydrogen absorption-desorption cycling stability is assessed by titration measurements. Finally, the kinetic behaviour and the reversible hydrogen storage capacity of the Li-RHC are discussed. © 2018 by the authors.

Reaction kinetic behaviour and cycling stability of the 2LiBH4-MgH2 reactive hydride composite (Li-RHC) are experimentally determined and analysed as a basis for the design and development of hydrogen storage tanks. Furthermore, the hydrogen absorption-desorption cycling stability is assessed by titration measurements.

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This work discusses the influence of different metal hydride storage bed configurations. The objective was to design and optimize a solid-state hydrogen storage for a nonpolluting mobility. A study of the absorption and desorption dynamics of a loose powder bed was performed first, followed by three different storage bed configurations: compacted Ti-Mn alloy powder, alternated Ti-Mn alloy compacts with stainless steel fins and compacted [Ti-Mn alloy/Stainless steel] powder mixture. A numerical model was developed to simulate the heat transfer and the hydrogen absorption and desorption rates. The alternation and compact mixture configurations gave better heat transfer efficiencies, absorption and desorption rates and increased hydrogen storage densities. Indeed, an efficient heat transfer (between the tank and its surrounding fluid), a tailored porosity of the metal hydride storage bed and the addition of high thermal conductivity materials allowed the overall storage performance to be improved. Thus, the required time for loading/unloading hydrogen was reduced drastically. The alternation configuration would offer the additional advantage of a simple, inexpensive and efficient recycling procedure. © 2019

This work discusses the influence of different metal hydride storage bed configurations. A study of the absorption and desorption dynamics of a loose powder bed was performed first, followed by three different storage bed configurations: compacted Ti-Mn alloy powder, alternated Ti-Mn alloy compacts with stainless steel fins and compacted [Ti-Mn alloy/Stainless steel] powder mixture.

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The features of gas discharge and plasma sources based on Penning trap with metal hydride cathodes are presented. In such devices, metal hydrides fulfill the functions of both a cathode and the solid-state generator of working gas. Their advantages are high purity of gas injected (99.99 - 99.999%), along with the safety and compactness in storage. Hydrogen is injected (desorbed) locally under the influence of ion bombardment of metal hydride surface, which fact provides return coupling between the intensity of gas desorption and the parameters of gas discharge. The rate of sputtering for those materials by plasma ions significantly reduces as well as heat loads. Above effect is achieved due to the creation of protective gas target as a result of both the thermal decomposition of metal hydride and ion stimulated desorption. The feature of metal hydride cathode under the conditions of gas discharge is a decrease in the ionization potential of desorbed hydrogen by 0.3-0.5 eV due to the molecules desorption in the vibrationally/rotationally excited state. This permits a substantially increase in ionization efficiency and the formation of negative ions by the mechanism of dissociative attachment in plasma volume. However, hydrogen desorbed from metal hydride significantly changes the properties of the discharge. This is expressed, for example, in the fact that the plasma source based on Penning trap with metal hydride cathode appears to generate current-compensated ion beams with the ability to control the energy of the extracted ions. There is also the opportunity of longitudinal extraction of negative hydrogen ions against the traditional method of extraction across the magnetic field. © 2018 Nova Science Publishers, Inc.

The features of gas discharge and plasma sources based on Penning trap with metal hydride cathodes are presented. Their advantages are high purity of gas injected (99.99 - 99.999%), along with the safety and compactness in storage.

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Hydrogen storage is vital for use in fuel cells and nuclear thermal rockets (NTR), both of which benefit from low-energy reservoirs available for long durations. A novel method of solid-state storage using catalytically-modified porous silicon can be fabricated entirely from materials found on the Moon and in asteroids, requiring only a fixed quantity of reusable reagents to be brought from Earth. Consumables include silicon, aluminum, iron, and water, all of which can be extracted from suitable regolith ore bodies. An aluminum pressure vessel containing granular porous silicon particles is recharged by hydrogen pressures of 0.8 MPa. Once charged, the hydrogen storage subsystem can be maintained at any temperature from 0 to 373 K for an indefinite period, suitable for lunar nights or months-long trips to main-belt asteroids. Discharge is facilitated by heating above 393 K, provided by IR, resistive, or metal foam heat conductors embedded in the particulate bed. Systems-level volumetric and gravimetric storage metrics are 39 g/l and 5.8 percent w/w, respectively, comparable to cryogenic hydrogen storage in size and mass. The embodied energy in storing the hydrogen is very small, less than 2 percent of the embodied chemical energy, which makes it more efficient than cryogenic at 40 percent. Silicon and aluminum can be extracted from regolith using isotopic separation by charge/mass ratio. Iron and nickel are harvested from lunar regolith by electromagnets and used as the catalyst to mediate between gaseous hydrogen and monatomic surface adsorbed hydrogen. Deposition is accomplished via carbonyl gases, which require a quantity of CO, which is recovered after each use. Making the silicon porous requires hydrofluoric acid (HF), which will need to be supplied from Earth. The hydrofluorosilicic acid byproduct can be heated to decompose into HF vapor and silicon dioxide. The HF is condensed and re-used, and the silicon dioxide is a waste byproduct, which can be formed into quartz objects such as portals and glassware. A lunar factory with a mass of 7.5 MT can produce complete hydrogen storage vessels, assuming that electronic control can be provided by the remainder of the power system. With granular media, the size and shape of such vessels are essentially constrained. One example is two-meter thick shell sections for a deep space crew cabin for radiation protection. The hydrogen therein could be withdrawn as a back-up supply of fuel, or for a final Hohman transfer burn just before refueling. © 2020 by the International Astronautical Federation (IAF). All rights reserved.

Consumables include silicon, aluminum, iron, and water, all of which can be extracted from suitable regolith ore bodies. An aluminum pressure vessel containing granular porous silicon particles is recharged by hydrogen pressures of 0.8 MPa.

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Renewable energy sources are becoming more and more widespread and practical used, but it is difficult to plan and stabilize the process of obtaining and storing this kind of energy. The hydrogen like an energy carrier is a possible decision for stable energy storage. Thanks to the hydrogen solid state storage systems based on metal hydrides is possible to store the energy, comes from renewable sources under safety and easy conditions. Historical methods of hydrogen storage like compression and liquefaction, which are established and developed now, still bring big safety problems and associated high costs of compression and cooling. © 2018 IEEE.

The hydrogen like an energy carrier is a possible decision for stable energy storage. Thanks to the hydrogen solid state storage systems based on metal hydrides is possible to store the energy, comes from renewable sources under safety and easy conditions.

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A solid-state hydrogen storage material comprising ammonia borane (AB) and polyethylene oxide (PEO) has been produced by freeze-drying from aqueous solutions from 0% to 100% AB by mass. The phase mixing behaviour of AB and PEO has been investigated using X-ray diffraction which shows that a new ‘intermediate’ crystalline phase exists, different from both AB and PEO, as observed in our previous work (Nathanson et al., 2015). It is suggested that hydrogen bonding interactions between the ethereal oxygen atom (–O–) in the PEO backbone and the protic hydrogen atoms attached to the nitrogen atom (N–H) of AB molecules promote the formation of a reaction intermediate, leading to lowered hydrogen release temperatures in the composites, compared to neat AB. PEO also acts to significantly reduce the foaming of AB during hydrogen release. A temperature-composition phase diagram has been produced for the AB-PEO system to show the relationship between phase mixing and hydrogen release. © 2018 The Author(s)

The phase mixing behaviour of AB and PEO has been investigated using X-ray diffraction which shows that a new ‘intermediate’ crystalline phase exists, different from both AB and PEO, as observed in our previous work (Nathanson et al., 2015). PEO also acts to significantly reduce the foaming of AB during hydrogen release.

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Intermetallic compounds are key materials for energy transition as they form reversible hydrides that can be used for solid state hydrogen storage or as anodes in batteries. ABy compounds (A = Rare Earth (RE); B = transition metal; 2 < y < 5) are good candidates to fulfill the required properties for practical applications. They can be described as stacking of [AB5] and [AB2] sub-units along the c crystallographic axis. The latter sub-unit brings a larger capacity, while the former one provides a better cycling stability. However, ABy binaries do not show good enough properties for applications. Upon hydrogenation, they exhibit multiplateau behavior and poor reversibility, attributed to H-induced amorphization. These drawbacks can be overcome by chemical substitutions on the A and/or the B sites leading to stabilized reversible hydrides. The present work focuses on the pseudo-binary Sm2MnxNi7-x system (0 ≤ x < 0.5). The structural, thermodynamic and corrosion properties are analyzed and interpreted by means of X-ray diffraction, chemical analysis, scanning electron microscopy, thermogravimetric analysis and magnetic measurements. Unexpected cell parameter variations are reported and interpreted regarding possible formation of structural defects and uneven Mn distribution within the Ni sublattice. Reversible capacity is improved for x > 0.3 leading to larger and flatter isotherm curves, allowing for reversible capacity >1.4 wt %. Regarding corrosion, the binary compound corrodes in alkaline medium to form rare earth hydroxide and nanoporous nickel. As for the Mn-substituted compounds, a new corrosion product is formed in addition to those above mentioned, as manganese initiates a sacrificial anode mechanism taking place at the early corrosion stage. © 2020 by the authors.

ABy compounds (A = Rare Earth (RE); B = transition metal; 2 < y < 5) are good candidates to fulfill the required properties for practical applications. Regarding corrosion, the binary compound corrodes in alkaline medium to form rare earth hydroxide and nanoporous nickel.

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The secondary energy sources, like hydrogen, is a key enabling energy carrier for the advancement of fuel cell technology. Hydrogen has a low volumetric energy density; therefore, its transportation is costly, and requires a large area. Solid-state hydrogen storage is a key solution for the promoting hydrogen in stationary power, portable power, and transportation applications. To keep these challenges up, this paper integrates production design of a novel solid-state-nanosized-mixed metal oxides (MMOs), CuCe2(MoO4)4 nanostructures via Pechini method, structural and morphological assessments, and its respective hydrogen storage properties. The electrochemical properties of the samples with morphological diversity have unveiled an exceeded discharge capacity (∼1320 mA h/g) of the sample which designed in neutral medium (pH = 7), having a specific surface area of 7.90 m2 g−1 and mean pore size of 37.07 nm. © 2020 Elsevier B.V.

The secondary energy sources, like hydrogen, is a key enabling energy carrier for the advancement of fuel cell technology. To keep these challenges up, this paper integrates production design of a novel solid-state-nanosized-mixed metal oxides (MMOs), CuCe2(MoO4)4 nanostructures via Pechini method, structural and morphological assessments, and its respective hydrogen storage properties.

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Hydrogen has been considered as a potential candidate for the replacement of fossil fuels in future due to its renewability, abundance, ease in production, environmental friendliness and high energy efficiency. In this regard, chemical storage of hydrogen in solid state of metal hydrides is the safest method for stationary and portable applications since these can be functioned at lower pressure and ambient temperature. Among the desirable metal hydrides, the intermetallic compound TiFe of cubic CsCl-type structure is well known for absorbing hydrogen reversibly up to 1.9 wt.% to form β-FeTiH and γ-FeTiH2 phases. In this paper, we have discussed the historic background outlining the recent developments on the microstructural modifications, activation kinetics and processing routes of TiFe intermetallic alloys toward the improvement of hydrogenation properties. An in-depth microstructural analysis of TiFe alloys has been presented in terms of crystallography, hydride phase formation and hydrogenation mechanisms. The rate-controlling steps for the mechanisms of (de)hydrogenation processes of TiFe intermetallics have been explained in details. It was found that the rate-controlling steps of the hydriding reaction were dependent on the fraction of β-hydride phase. Intensive research activities were carried out to improve the first hydrogenation kinetics that can be categorized into two groups: alloying and mechanical activation. The mechanisms for improved hydrogenation kinetics in both cases have been explained. Lastly, various fabrication processes to produce TiFe alloys have been presented and correlated with cost-effectiveness and hydrogen-storage capability. Therefore, the focus of this article is to present the basic knowledge and recent developments on TiFe intermetallic alloys for future hydrogen-storage applications which will be beneficial to researchers and practitioners in the field of interest. © 2019 Taylor & Francis Group, LLC.

In this regard, chemical storage of hydrogen in solid state of metal hydrides is the safest method for stationary and portable applications since these can be functioned at lower pressure and ambient temperature. Intensive research activities were carried out to improve the first hydrogenation kinetics that can be categorized into two groups: alloying and mechanical activation.

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Hydrogen is an ideal energy carrier because of its high chemical energy, environmental friendliness and renewability. In order to realize the safe, efficient and compact hydrogen storage, various solid-state hydrogen storage materials based on the physisorption or chemisorption of hydrogen have been developed over the past decades. Among them, magnesium hydride, MgH2, is identified as one of the most promising candidates due to its high hydrogen storage density, low cost and abundance of Mg element. However, the sluggish kinetics and high thermodynamic stability of MgH2 result in its high operation temperature and low hydrogen sorption rate, impeding its practical application. In this article, the recent progress in catalysis and nanoconfinement effects on the hydrogen storage properties of MgH2 is comprehensively reviewed. In particular, the synergetic roles of catalysis and nanoconfinement in MgH2 are highlighted. Furthermore, the future challenges and prospects of emerging research for MgH2 are discussed. It is suggested that the nonmetal-doped porous carbon materials could be a class of ideal additives to enhance the hydrogen storage properties of MgH2 by the synergetic effects of catalysis and nanoconfinement. © 2017 Hydrogen Energy Publications LLC

Among them, magnesium hydride, MgH2, is identified as one of the most promising candidates due to its high hydrogen storage density, low cost and abundance of Mg element. Furthermore, the future challenges and prospects of emerging research for MgH2 are discussed.

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Characterising the hydrogen sorption properties of materials is important for a range of applications, including solid state hydrogen storage, electrochemical and thermal energy storage using metal hydrides, and H2 gas compression and purification. However, it can be technically demanding and subject to significant error if not performed with care. In this article, potential pitfalls in the performance of hydrogen sorption measurements are discussed. The topics covered include instrument design and calibration, sample size choice, sample and gas purity, isotherm measurement procedure and issues associated with data reduction. Approaches to validating equipment and isotherm measurements are also discussed. Different sample types are considered, including metal and complex hydrides and nanoporous adsorbents, such as porous carbons, zeolites and metal-organic frameworks (MOFs). © 2017 Hydrogen Energy Publications LLC

However, it can be technically demanding and subject to significant error if not performed with care. Approaches to validating equipment and isotherm measurements are also discussed.

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The pyroelectric effect is commonly used to construct infrared radiation detectors. To pay attention to the possibility of using this phenomenon in materials based on relaxor-ferroelectric such as Pb(Mg1/3Nb2/3)1-xTixO3 (lead titanium-lead magnesium niobate), single crystals from solid solution were grown using modified Bridgman method with x taken three different range (x = 0.25, 0.33 and 0.40). In this work the operation principles for pyroelectric sensor and their properties are presented, with a brief review on the temperature stability of the Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–xPT)single crystals. It was shown that the pyroelectric and dielectric properties are strongly dependent on composition (PT content), as well as the temperature variation. The investigations have revealed that the best choice for pyroelectric performances is <111>oriented PMN–0.25 PT, although, the PMN–0.33 PT and PMN–0.40 PT owns much better temperature stability, and higher Curie temperature Tc. The PMN–xPT single crystals showed promising pyroelectric performances, they can be used as thermal sensors and may be associated with temperature management systems to improve the performance of solid state hydrogen reactors. © 2019 Hydrogen Energy Publications LLC

To pay attention to the possibility of using this phenomenon in materials based on relaxor-ferroelectric such as Pb(Mg1/3Nb2/3)1-xTixO3 (lead titanium-lead magnesium niobate), single crystals from solid solution were grown using modified Bridgman method with x taken three different range (x = 0.25, 0.33 and 0.40). The PMN–xPT single crystals showed promising pyroelectric performances, they can be used as thermal sensors and may be associated with temperature management systems to improve the performance of solid state hydrogen reactors.

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De/rehydrogenation performances and reaction pathways of nanoconfined 2LiBH4[sbnd]MgH2 into activated carbon (AC) packed in small hydrogen storage tank are proposed for the first time. Total and material storage capacities upon five hydrogen release and uptake cycles are 3.56–4.55 and 2.03–3.28 wt % H2, respectively. Inferior hydrogen content to theoretical capacity (material capacity of 5.7 wt % H2) is due to partial dehydrogenation during sample preparation and incomplete decomposition of LiBH4 as well as the formation of thermally stable Li2B12H12 upon cycling. Two-step dehydrogenation of MgH2 and LiBH4 to produce Mg and MgB2+LiH, respectively is found at all positions in the tank. For rehydrogenation, reversibility of MgH2 and LiBH4 proceeds via different reaction mechanisms. Although isothermal condition (Tset = 350 °C) and controlled pressure range (e.g., 30–40 bar H2 for hydrogenation) are applied, temperature gradient inside the tank and poor hydrogen diffusion through hydride bed, especially in the sample bulk are detected. This results in alteration of de/rehydrogenation pathways of hydrides at different positions in the tank. Thus, further development of hydrogen storage tank based 2LiBH4[sbnd]MgH2 nanoconfined in AC includes the improvement of thermal conductivity of materials and temperature control system as well as hydrogen permeability. © 2019 Hydrogen Energy Publications LLC

De/rehydrogenation performances and reaction pathways of nanoconfined 2LiBH4[sbnd]MgH2 into activated carbon (AC) packed in small hydrogen storage tank are proposed for the first time. Although isothermal condition (Tset = 350 °C) and controlled pressure range (e.g., 30–40 bar H2 for hydrogenation) are applied, temperature gradient inside the tank and poor hydrogen diffusion through hydride bed, especially in the sample bulk are detected.

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LaNi5 alloy can be utilized to directly store and release hydrogen in mild condition, thus it is considered as a long-term safe and stable solid-state hydrogen storage material. In this work, LaNi5H5 was used as the solid-state hydrogen source in the CO2 methanation reaction. Impressively, the carbon dioxide conversion can be achieved to nearly 100% under 3 MPa mixed gas at 200 °C. The microstructure and composition analysis results reveal that the high catalytic activity may originate from the promoted elementary steps over in situ formed metallic Ni nanoparticles during the CO2 methanation process. More importantly, as the lowered reaction temperature prevented the agglomeration of Ni nanoparticles, this catalyst exhibited durable stability with 99% conversion rate of CO2 retained after 400 h cycling test. © 2019 Hydrogen Energy Publications LLC

Impressively, the carbon dioxide conversion can be achieved to nearly 100% under 3 MPa mixed gas at 200 °C. More importantly, as the lowered reaction temperature prevented the agglomeration of Ni nanoparticles, this catalyst exhibited durable stability with 99% conversion rate of CO2 retained after 400 h cycling test.

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Solid-state hydrogen storage materials undergo complex phase transformations whose behavior are collectively determined by thermodynamic (e.g., Gibbs free energy), mechanical (e.g., lattice and elastic constants), and mass transport (e.g., diffusivity) properties. These properties depend on the reaction conditions and evolve continuously during (de)hydrogenation. Thus, they are difficult to measure in experiments. Because of this, past progress to improve solid-state hydrogen storage materials has been prolonged. Using PdHx as a representative example for interstitial metal hydride, we have recently applied molecular dynamics simulations to quantify hydrogen diffusion in the entire reaction space of temperature and composition. Here, we have further applied molecular dynamics simulations to obtain well-converged expressions for lattice constants, Gibbs free energies, and elastic constants of PdHx at various stages of the reaction. Our studies confirm significant dependence of elastic constants on temperature and composition. Specifically, a new dynamic effect of hydrogen diffusion on elastic constants is discovered and discussed. © 2018 U.S. Government.

Using PdHx as a representative example for interstitial metal hydride, we have recently applied molecular dynamics simulations to quantify hydrogen diffusion in the entire reaction space of temperature and composition. Specifically, a new dynamic effect of hydrogen diffusion on elastic constants is discovered and discussed.

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Hydrogen storage in the solid state represents one of the most attractive and challenging ways to supply hydrogen to a proton exchange membrane (PEM) fuel cell. Although in the last 15 years a large variety of material systems have been identified as possible candidates for storing hydrogen, further efforts have to be made in the development of systems which meet the strict targets of the Fuel Cells and Hydrogen Joint Undertaking (FCH JU) and U.S. Department of Energy (DOE). Recent projections indicate that a system possessing: (i) an ideal enthalpy in the range of 20-50 kJ/mol H2, to use the heat produced by PEM fuel cell for providing the energy necessary for desorption; (ii) a gravimetric hydrogen density of 5 wt. % H2 and (iii) fast sorption kinetics below 110 °C is strongly recommended. Among the known hydrogen storage materials, amide and imide-based mixtures represent the most promising class of compounds for on-board applications; however, some barriers still have to be overcome before considering this class of material mature for real applications. In this review, the most relevant progresses made in the recent years as well as the kinetic and thermodynamic properties, experimentally measured for the most promising systems, are reported and properly discussed. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.

Hydrogen storage in the solid state represents one of the most attractive and challenging ways to supply hydrogen to a proton exchange membrane (PEM) fuel cell. Among the known hydrogen storage materials, amide and imide-based mixtures represent the most promising class of compounds for on-board applications; however, some barriers still have to be overcome before considering this class of material mature for real applications.

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Polygeneration Microgrids (PMG) can be configured to deliver multiple outputs such as, electricity, heat, cold, fuel (hydrogen) and clean water. In an earlier paper the authors presented an analysis of a PMG consisting of solar photovoltaic field, fuel cell, solid state hydrogen storage and electrolyzer using commercial software HOMER. Keeping in mind the fact that battery storage is preferred for stand-alone microgrids, in this paper, the influence of battery storage on the performance of a PMG is presented. An added advantage of solid state hydrogen storage – fuel cell system is the availability heat released during adsorption of metal hydride in addition to that rejected by the fuel cell. A comparison of battery alone versus battery + fuel cell is made. © 2020 Elsevier Ltd

Polygeneration Microgrids (PMG) can be configured to deliver multiple outputs such as, electricity, heat, cold, fuel (hydrogen) and clean water. An added advantage of solid state hydrogen storage – fuel cell system is the availability heat released during adsorption of metal hydride in addition to that rejected by the fuel cell.

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Magnesium hydride (MgH2) and titanium hydride (TiH2) are two potential candidates for solid-state hydrogen storage, but strong hydride formation energy in these hydrides undesirably results in their high dehydrogenation temperature. First-principles calculations show that the metastable hydrides in the MgH2–TiH2 system have low hydrogen binding energy, which makes them more appropriate for low-temperature hydrogen storage. In this study, severe plastic deformation (SPD) via the high-pressure torsion (HPT) method is applied to the MgH2–TiH2 system to synthesize metastable hydrides. While MgH2 transforms to a high-pressure orthorhombic γ phase, TiH2 does not exhibit any cubic-to-tetragonal phase transformation even by HPT processing at cryogenic temperature. Application of large strains by 400 HPT turns to the immiscible MgH2/TiH2 composite results in atomic-scale mixing and formation of nanostructured ternary Mg–Ti–H hydride with the metastable FCC structure and lower dehydrogenation temperature than TiH2. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

First-principles calculations show that the metastable hydrides in the MgH2–TiH2 system have low hydrogen binding energy, which makes them more appropriate for low-temperature hydrogen storage. Application of large strains by 400 HPT turns to the immiscible MgH2/TiH2 composite results in atomic-scale mixing and formation of nanostructured ternary Mg–Ti–H hydride with the metastable FCC structure and lower dehydrogenation temperature than TiH2.

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Hydrogen, which holds tremendous promise as a new clean energy option is considered as an efficient source of primary energy. Unluckily, hydrogen storage presents the most crucial difficulty restricting utilization of hydrogen energy for real applications. However, Mg metal is the best known cheap solid-state hydrogen storage media with high hydrogen capacity and operational cost effectiveness; it shows high thermal stability and poor hydrogenation/dehydrogenation kinetics. In the present work we have succeeded to prepare nanocrystalline MgH2 powders doped with a mixture of 8 wt% Nb2O5/2 wt% Ni nanocatalytic system. The synthesized nanocomposite powders possessed superior hydrogenation/dehydrogenation kinetics (2.6 min/3 min) at relatively low temperature (250 °C) with long cycle-life-time (400 h). The powders were consolidated into green-compacts, using cold pressing technique. The compacts were utilized as solid-state hydrogen source needed for charging a battery of a cell-phone device, using integrated Ti-tank/commercial proton-exchange membrane fuel cell system. © 2018 Hydrogen Energy Publications LLC

However, Mg metal is the best known cheap solid-state hydrogen storage media with high hydrogen capacity and operational cost effectiveness; it shows high thermal stability and poor hydrogenation/dehydrogenation kinetics. The synthesized nanocomposite powders possessed superior hydrogenation/dehydrogenation kinetics (2.6 min/3 min) at relatively low temperature (250 °C) with long cycle-life-time (400 h).

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The present work reports for the first time application of cold spray coating for doping plastically deformed Mg-strips by different concentrations of fine Ni powders. For present study, Mg rods were cold-rolled for 300 passes and then coated by Ni fine powders, using a cold spray process operated at 150 °C under high argon gas pressure. The Ni powders were pelted into Mg-substrate through the high-velocity jet at a speed of 500 m/s. Under these preparation conditions, Ni powders were plastically deformed at the surface of Mg strips to create numerous pores and cavities, worked as hydrogen diffusion gateway. The as-coated Mg sheets with 3-Ni layers (5.28 wt%) possessed good hydrogenation/dehydrogenation kinetics, implied by a short absorption/desorption time (5.1/11 min) of 6.1 wt% hydrogen at 150 °C/10 bar and 200 °C/200 mbar, respectively. The fabricated solid-state hydrogen storage nanocomposite strips revealed good cyclability of achieving 600 cycles at 200 °C without failure of degradation. © 2019 Hydrogen Energy Publications LLC

For present study, Mg rods were cold-rolled for 300 passes and then coated by Ni fine powders, using a cold spray process operated at 150 °C under high argon gas pressure. Under these preparation conditions, Ni powders were plastically deformed at the surface of Mg strips to create numerous pores and cavities, worked as hydrogen diffusion gateway.

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Alkali hydrazinidoboranes MN2H3BH3 (M = Li, Na, K, Rb) have been developed for hydrogen storage. To complete the family of MN2H3BH3, we focused on cesium hydrazinidoborane CsN2H3BH3 (CsHB). It has been synthesized by reaction of cesium with hydrazine borane (N2H4BH3) at −20 °C under inert atmosphere, and it has been characterized. A crystalline solid (monoclinic, s.g. P21 (No. 4)) has been obtained. Its potential for hydrogen storage has been studied by combining different techniques. It was found that, under heating at constant heating rate (5 °C min−1) or at constant temperature (e.g. 120 °C), CsHB decomposes rather than it dehydrogenates. It releases several unwanted gaseous products (e.g. NH3, B2H6) together with H2, and transforms into a residue that poses safety issues because of shock-sensitivity and reactivity towards O2/H2O. Though the destabilization brought by Cs+ onto the anion [N2H3BH3]− has been confirmed, the effect is not efficient enough to avoid the aforementioned drawbacks. All of our results are presented herein and discussed within the context of solid-state hydrogen storage. © 2020 Hydrogen Energy Publications LLC

Alkali hydrazinidoboranes MN2H3BH3 (M = Li, Na, K, Rb) have been developed for hydrogen storage. Its potential for hydrogen storage has been studied by combining different techniques.

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It is known that the hydrogen has a very high mass energy density, in fact, that it is a lightest gas; therefore, its storage is a great problem. The aim of the hydrogen storage technologies is thus to reduce the volume that hydrogen occupies in its thermodynamically stable state under conditions close to ambient salt. Recent work on hydrogen storage is mainly based on the use of metal hydrides. These metal hydrides have a high capacity for the hydrogen storage in the operating conditions. The effecting parameters on the performance of such a metal-hydrogen reactor are its design and configuration. In this case, there are a number of problems that need to be considered in designing a reactor. Among these parameters are the reactor configuration, the thermal and the mechanical strength, the kinetics of hydrogen storage and the security. Our study is concentrated on the problem of the thermal and the mechanical strength while focusing on the nature of the metal makes the reactor. In this work, the experimental studies of the hydrogen absorption phenomenon in different reactors, based on metal hydrides, were evaluated. The characteristics of the reaction kinetics in three different reactors using the same measurement conditions were compared. A numerical model describing the reaction kinetic of the H2 absorption by LaNi5 alloy validates the results were obtained. Of these results, it is found that the rate constant varies from one reactor to another. Moreover, the activation energy of the absorption kinetics were identified. © 2017

In this work, the experimental studies of the hydrogen absorption phenomenon in different reactors, based on metal hydrides, were evaluated. Of these results, it is found that the rate constant varies from one reactor to another.

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Hydrogen as an energy carrier is very versatile in energy storage applications. Developments in novel, sustainable technologies towards a CO2-free society are needed and the exploration of all-solid-state batteries (ASSBs) as well as solid-state hydrogen storage applications based on metal hydrides can provide solutions for such technologies. However, there are still many technical challenges for both hydrogen storage material and ASSBs related to designing low-cost materials with low-environmental impact. The current materials considered for all-solid-state batteries should have high conductivities for Na+, Mg2+ and Ca2+, while Al3+-based compounds are often marginalised due to the lack of suitable electrode and electrolyte materials. In hydrogen storage materials, the sluggish kinetic behaviour of solid-state hydride materials is one of the key constraints that limit their practical uses. Therefore, it is necessary to overcome the kinetic issues of hydride materials before discussing and considering them on the system level. This review summarizes the achievements of the Marie Sklodowska-Curie Actions (MSCA) innovative training network (ITN) ECOSTORE, the aim of which was the investigation of different aspects of (complex) metal hydride materials. Advances in battery and hydrogen storage materials for the efficient and compact storage of renewable energy production are discussed. © 2020 by the authors.

Developments in novel, sustainable technologies towards a CO2-free society are needed and the exploration of all-solid-state batteries (ASSBs) as well as solid-state hydrogen storage applications based on metal hydrides can provide solutions for such technologies. However, there are still many technical challenges for both hydrogen storage material and ASSBs related to designing low-cost materials with low-environmental impact.

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Hydrogen storage in transition mixed metal oxides (MMOs) are predicted from their tendency for adsorption-desorption hydrogen. Hydrogen itself requires initial forces pressure for initiation of condensation. MMOs, based on their effective immobilization matrices, are potential nanocatalysts for energy storage. Even various materials are highlighted for hydrogen storage; however, their adsorption capacities are insufficient for real applications. Here we report, for the first time, a novel hydrogen storage MMOs (Sr2Co9O14 nanoparticles) potential for physical hydrogen sorption, containing a redox species. This polycrystalline nanoparticle is prepared via a combustion method in the presence of various fuels like glucose, fructose, sucrose, lactose, and maltose. The glucose supports the pure and homogenous formation of Sr2Co9O14 nanoparticles consisting the particles less than 100 nm. Interestingly, a maximum discharge capacity of around 950 mA h/g at room temperature has recorded; emphasizing Sr2Co9O14 nanoparticles is a potential substrate for hydrogen storage. © 2019 Hydrogen Energy Publications LLC

MMOs, based on their effective immobilization matrices, are potential nanocatalysts for energy storage. This polycrystalline nanoparticle is prepared via a combustion method in the presence of various fuels like glucose, fructose, sucrose, lactose, and maltose.

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To enhance the dehydrogenation/rehydrogenation kinetic behavior of the LiBH4-MgH2 composite system, TiF4 is used as an additive. The effect of this additive on the hydride composite system has been studied by means of laboratory and advanced synchrotron techniques. Investigations on the synthesis and mechanism upon hydrogen interaction show that the addition of TiF4 to the LiBH4-MgH2 composite system during the milling procedure leads to the in situ formation of well-distributed nanosized TiB2 particles. These TiB2 nanoparticles act as nucleation agents for the formation of MgB2 upon dehydrogenation process of the hydride composite system. The effect of TiB2 nanoparticles is maintained upon cycling. © 2018 American Chemical Society.

The effect of this additive on the hydride composite system has been studied by means of laboratory and advanced synchrotron techniques. The effect of TiB2 nanoparticles is maintained upon cycling.

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This paper presents the results related to the investigation of layers of nanocrystalline silicon carbide (nc-SiC) obtained by direct ion deposition for the purpose of hydrogen accumulation. The parameters of the production process providing the largest amount of accumulated hydrogen (more than 5.5 wt.%) were determined based on the mass spectrometric data on the desorption of atomic and molecular hydrogen from nc-SiC films. Electron microscopic examination revealed the structural features that are responsible for absorption, retention, and desorption of hydrogen at relatively low temperatures and pressures. The study results suggest that the main structural elements acting as the hydrogen traps are the vacant positions of carbon in nc-SiC. The presence of a developed system of intercrystalline boundaries in investigated films promotes the hydrogen desorption at relatively low temperatures. Copyright © 2018 A. Guglya et al.

Electron microscopic examination revealed the structural features that are responsible for absorption, retention, and desorption of hydrogen at relatively low temperatures and pressures. The presence of a developed system of intercrystalline boundaries in investigated films promotes the hydrogen desorption at relatively low temperatures.

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Hydrogen storage in solids of hydrides is advantageous in comparison to gaseous or liquid storage. Magnesium based materials are being studies for solid-state hydrogen storage due to their advantages of high volumetric and gravimetric hydrogen storage capacity. However, unfavorable thermodynamic and kinetic barriers hinder its practical application. In this work, we presented that kinetics of Mg-based composites were significantly improved during high energy ball milling in presence of various types of carbon, including plasma carbon produced by plasma-reforming of hydrocarbons, activated carbon, and carbon nanotubes. The improvement of the kinetics and de-/re-hydrogenation performance of MgH2 and TiC-catalysed MgH2 by introduction of carbon are strongly dependent on the milling time, amount of carbon and carbon structure. The lowest dehydrogenation temperature was observed at 180 °C by the plasma carbon–modified MgH2/TiC. We found that nanoconfinement of carbon structures stabilised Mg-based nanocomposites and hinders the nanoparticles growth and agglomeration. Plasma carbon was found to show better effects than the other two carbon structures because the plasma carbon contained both few layer graphene sheets that served as an active dispersion matrix and amorphous activated carbons that promoted the spill-over effect of TiC catalysed MgH2. The strategy in enhancing the kinetics and thermodynamics of Mg-based composites is leading to a better design of metal hydride composites for hydrogen storage. © 2018 Hydrogen Energy Publications LLC

Plasma carbon was found to show better effects than the other two carbon structures because the plasma carbon contained both few layer graphene sheets that served as an active dispersion matrix and amorphous activated carbons that promoted the spill-over effect of TiC catalysed MgH2. The strategy in enhancing the kinetics and thermodynamics of Mg-based composites is leading to a better design of metal hydride composites for hydrogen storage.

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Mg-based hybrids have shown promise via enhanced hydrogen storage properties. The Mg–Mg2Ni-carbon hybrid can be synthesized by accumulative roll bonding (ARB), which is amenable to ‘scaled-up’ synthesis. In spite of the ‘bulk’ nature of the samples synthesized, they display fast kinetics of absorption and desorption of hydrogen. In the current work, we try to comprehend the basis for the same in terms of the activation energy of the underlying processes involved; via desorption curves (wt.% H - time curves) in a Sievert's apparatus and differential scanning calorimetry (heat evolved - T plots). Analysis invoking the Johnson-Mehl-Avrami model and Kissinger plots show that the significantly reduced activation energy for the dehydrogenation process in the hybrid is responsible for the rapid kinetics. It is evinced that admixing the additives with Mg, coupled with fine scale microstructure rich in interfaces is responsible for the fast kinetics. It is established that the rate limiting step for hydrogen desorption is interface migration and not the diffusion of hydrogen, which is governed by the JMA-3D model. © 2020 Hydrogen Energy Publications LLC

Mg-based hybrids have shown promise via enhanced hydrogen storage properties. The Mg–Mg2Ni-carbon hybrid can be synthesized by accumulative roll bonding (ARB), which is amenable to ‘scaled-up’ synthesis.

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Solid-state hydrogen storage may be the only promising way for mobile applications of hydrogen energy since it is safe, quickly reversible, cost-efficient, and has a high volumetric energy density under standard conditions. Silsesquioxane and its derivatives seem well suited for solid-state hydrogen storage and have attracted many experimental and theoretical researchers. In the present work, we have systematically studied four cages of T8, T10, and T12 (D2d and D6h) for hydrogen storage including adsorption and encapsulation of hydrogen molecules. We find that silsesquioxane cages have up to about 4150 m2/g specific surface area (SSA) and 7.81 wt % for hydrogen storage. These calculated values are comparable to the highest hydrogen storage values of metal-organic frameworks, porous polymer networks, and covalent organic frameworks. In addition, we use the quasi-dynamic method to study the encapsulation of hydrogen molecules into these cages because of the timescale limitation of ab initio molecular dynamics. Thermodynamic parameters such as enthalpy and Gibbs free energy at different temperatures are calculated during the insertion processes. We find that the insertion process of a hydrogen molecule into the T12 (D6h) cage is almost energy-conserved and its energy barriers of enthalpy and free energy are moderate under standard conditions. Copyright © 2020 American Chemical Society.

We find that silsesquioxane cages have up to about 4150 m2/g specific surface area (SSA) and 7.81 wt % for hydrogen storage. Thermodynamic parameters such as enthalpy and Gibbs free energy at different temperatures are calculated during the insertion processes.

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We performed feasibility analysis of 10 kW hydrogen backup power system (H2BS) consisting of a water electrolyzer, a metal hydride hydrogen storage and a fuel cell. Capital investments in H2BS are mostly determined by the costs of the PEM electrolyzer, the fuel cell and solid state hydrogen storage materials, for single unit or small series manufacture the cost of AB5-type intermetallic compound can reach 50% of total system cost. Today the capital investments in H2BS are 3 times higher than in conventional lead-acid system of the same capacity. Wide distribution of fuel cell hydrogen vehicles, development of hydrogen infrastructure, and mass production of hydrogen power systems will for sure lower capital investments in fuel cell backup power. Operational expenditures for H2BS is only 15% from the expenditures for lead acid systems, and after 4-5 years of exploitation the total cost of ownership will become lower than for batteries. © Published under licence by IOP Publishing Ltd.

Capital investments in H2BS are mostly determined by the costs of the PEM electrolyzer, the fuel cell and solid state hydrogen storage materials, for single unit or small series manufacture the cost of AB5-type intermetallic compound can reach 50% of total system cost. Wide distribution of fuel cell hydrogen vehicles, development of hydrogen infrastructure, and mass production of hydrogen power systems will for sure lower capital investments in fuel cell backup power.

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For sustainable and incremental growth, mankind is adopting renewable sources of energy along with storage systems. Storing surplus renewable energy in the form of hydrogen is a viable solution to meet continuous energy demands. In this paper the concept of electrochemical hydrogen storage in a solid multi-walled carbon nanotube (MWCNT) electrode integrated in a modified unitized regenerative fuel cell (URFC) is investigated. The method of solid electrode fabrication from MWCNT powder and egg white as an organic binder is disclosed. The electrochemical testing of a modified URFC with an integrated MWCNT-based hydrogen storage electrode is performed and reported. Galvanostatic charging and discharging was carried out and results analyzed to ascertain the electrochemical hydrogen storage capacity of the fabricated electrode. The electrochemical hydrogen storage capacity of the porous MWCNT electrode is found to be 2.47 wt%, which is comparable with commercially available AB5-based hydrogen storage canisters. The obtained results prove the technical feasibility of a modified URFC with an integrated MWCNT-based hydrogen storage electrode, which is the first of its kind. This is surelya step forward towards building a sustainable energy economy. © 2019 by the authors.

The method of solid electrode fabrication from MWCNT powder and egg white as an organic binder is disclosed. The electrochemical testing of a modified URFC with an integrated MWCNT-based hydrogen storage electrode is performed and reported.

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Hydride-forming alloys are currently considered reliable and suitable hydrogen storage materials because of their relatively high volumetric densities, and reversible H2 absorption/desorption kinetics, with high storage capacity. Nonetheless, their practical use is obstructed by several factors, including deterioration and slow hydrogen absorption/desorption kinetics resulting from the surface chemical action of gas impurities. Lately, common strategies, such as spark plasma sintering, mechanical alloying, melt spinning, surface modification and alloying with other elements have been exploited, in order to overcome kinetic barriers. Through these techniques, improvements in hydriding kinetics has been achieved, however, it is still far from that required in practical application. In this review, we provide a critical overview on the effect of mechanical alloying of various metal hydrides (MHs), ranging from binary hydrides (CaH2, MgH2, etc) to ternary hydrides (examples being Ti-Mn-N and Ca-La-Mg-based systems), that are used in solid-state hydrogen storage, while we also deliver comparative study on how the aforementioned alloy preparation techniques affect H2 absorption/desorption kinetics of different MHs. Comparisons have been made on the resultant material phases attained by mechanical alloying with those of melt spinning and spark plasma sintering techniques. The reaction mechanism, surface modification techniques and hydrogen storage properties of these various MHs were discussed in detail. We also discussed the remaining challenges and proposed some suggestions to the emerging research of MHs. Based on the findings obtained in this review, the combination of two or more compatible techniques, e.g., synthesis of metal alloy materials through mechanical alloying followed by surface modification (metal deposition, metal-metal co-deposition or fluorination), may provide better hydriding kinetics. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

Nonetheless, their practical use is obstructed by several factors, including deterioration and slow hydrogen absorption/desorption kinetics resulting from the surface chemical action of gas impurities. Comparisons have been made on the resultant material phases attained by mechanical alloying with those of melt spinning and spark plasma sintering techniques.

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Ammine metal borohydrides show potential for solid-state hydrogen storage and can be tailored toward hydrogen release at low temperatures. Here, we report the synthesis and structural characterization of seven new ammine metal borohydrides, M(BH4)3·nNH3, M = La (n = 6, 4, or 3) or Ce (n = 6, 5, 4, or 3). The two compounds with n = 6 are isostructural and have new orthorhombic structure types (space group P21212) built from cationic complexes, [M(NH3)6(BH4)2]+, and are charge balanced by BH4-. The structure of Ce(BH4)3·5NH3 is orthorhombic (space group C2221) and is built from cationic complexes, [Ce(NH3)5(BH4)2]+, and charge balanced by BH4-. These are rare examples of borohydride complexes acting both as a ligand and as a counterion in the same compound. The structures of M(BH4)3·4NH3 are monoclinic (space group C2), built from neutral molecular complexes of [M(NH3)4(BH4)3]. The new compositions, M(BH4)3·3NH3 (M = La, Ce), among ammine metal borohydrides, are orthorhombic (space group Pna21), containing molecular complexes of [M(NH3)3(BH4)3]. A revised structural model for A(BH4)3·5NH3 (A = Y, Gd, Dy) is presented, and the previously reported composition A(BH4)3·4NH3 (A = Y, La, Gd, Dy) is proposed in fact to be M(BH4)3·3NH3 along with a new structural model. The temperature-dependent structural properties and decomposition are investigated by in situ synchrotron radiation powder X-ray diffraction in vacuum and argon atmosphere and by thermal analysis combined with mass spectrometry. The compounds with n = 6, 5, and 4 mainly release ammonia at low temperatures, while hydrogen evolution occurs for M(BH4)3·3NH3 (M = La, Ce). Gas-release temperatures and gas composition from these compounds depend on the physical conditions and on the relative stability of M(BH4)3·nNH3 and M(BH4)3 © 2020 American Chemical Society.

The two compounds with n = 6 are isostructural and have new orthorhombic structure types (space group P21212) built from cationic complexes, [M(NH3)6(BH4)2]+, and are charge balanced by BH4-. These are rare examples of borohydride complexes acting both as a ligand and as a counterion in the same compound.

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An analysis to hydrogen storage technologies, with major focus on the solid-state hydrogen storage is presented. A discussion on the physicochemical and thermodynamic aspects of the metal hydride formation is introduced, and the most common metal hydride compounds are analyzed. The necessity for the development of an accurate numerical analysis to describe the storage/release of hydrogen in metal hydrides and the establishment of an effective heat management is also explained and discussed. © 2018 Elsevier Inc. All rights reserved.

An analysis to hydrogen storage technologies, with major focus on the solid-state hydrogen storage is presented. A discussion on the physicochemical and thermodynamic aspects of the metal hydride formation is introduced, and the most common metal hydride compounds are analyzed.

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A new solid-state hydrogen storage system of magnesium hydride (MgH2) doped with 5 wt% of metallic glassy (MG) zirconium palladium (Zr2Pd) nanopowder was fabricated using a high-energy ball milling technique. The end-product obtained after 50 h of milling was consolidated into bulk buttons, using a hot-pressing technique at 350 °C. The results have shown that this consolidation step, followed by the repetitive pressing at ambient temperature did not affect the nanocrystalline characteristics of pressed powders. Recycling pressing demonstrated beneficial effects of plastic deformation and lattice imperfections on Mg, leading to its enhanced hydrogenation/dehydrogenation kinetics and cycle-life-time performance compared with untreated samples. The results elucidated that spherical, hard, nanopowder of MG-Zr2Pd were forced to penetrate the Mg/MgH2 matrix to create micro/nanopore structures upon pressing for 50 cycles. These ultrafine spherical metallic glassy particles (∼400 nm in diameter) acted as a micro-milling media for reducing the particle size of MgH2 powders into submicron particles. In addition, they played a vital role as grain growth inhibitors to prevent the undesired growth of Mg grains upon the application of a moderate temperature in the range of 50 °C to 350 °C. The apparent activation energy for the decomposition of this new consolidated nanocomposite material was measured to be 92.2 kJ mol-1, which is far below than the measured value of pure nanocrystalline MgH2 powders (151.2 kJ mol-1) prepared in the present study. This new binary system possessed superior hydrogenation kinetics, indicated by the rather low temperature (200 °C) required to uptake 6.08 wt% H2 within 7.5 min. More importantly, the system revealed excellent dehydrogenation kinetics at 225 °C as implied by the limited time needed to release 6.1 wt% H2 in 10 min. The MgH2/5 wt% MG-Zr2Pd system showed a high performance for cyclability, implied by the achievement of continuous cycles (338 cycles) at 225 °C without degradation over 227 h. This journal is © 2019 The Royal Society of Chemistry.

The end-product obtained after 50 h of milling was consolidated into bulk buttons, using a hot-pressing technique at 350 °C. This new binary system possessed superior hydrogenation kinetics, indicated by the rather low temperature (200 °C) required to uptake 6.08 wt% H2 within 7.5 min.

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In the framework of the European project SSH2S, a solid-state hydrogen storage tank - fuel cell system was demonstrated as Auxiliary Power Unit (APU) for a light duty vehicle. In this work, we have assessed the environmental impacts and the costs of the system developed. Following an eco-design approach, we have identified the processes mostly contributing to them and we have suggested possible improvements. By performing a Life Cycle Assessment (LCA), we found that, when the electricity consumption for hydrogen gas compression is included into the analysis, a solid-state hydrogen storage tank has similar greenhouse gas emissions and primary energy demand than those of type III and IV tanks. However, the resources depletion is higher for the solid-state system, even though the inclusions of the end of life of the APU and the recycling of the materials may result in different conclusions. The costs of an APU equipped with a solid-state hydrogen storage tank are significantly higher, about 1.5–2 times the systems based on type III and IV tanks. However, mature technologies are compared with a prototype, which has much room for optimization. To improve both the environmental and economic performances of the APU, a reduction of structural materials for both the solid-state hydrogen tank and Balance of Plant is recommended. © 2018 Elsevier Ltd

By performing a Life Cycle Assessment (LCA), we found that, when the electricity consumption for hydrogen gas compression is included into the analysis, a solid-state hydrogen storage tank has similar greenhouse gas emissions and primary energy demand than those of type III and IV tanks. However, mature technologies are compared with a prototype, which has much room for optimization.

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Hydrogen is a generally abundant, safe, clean and environmentally apt alternative fuel, which replenishes the void generated by depleting fossil fuel reserves. The adoption of hydrogen as an energy source has been restricted to low levels due to the complications associated with its viable storage and usage. Existing technologies, such as storage of hydrogen in compressed and liquefied forms are not adequate to meet the broad on-board applications. The gravimetric energy density (120 MJ/kg) of hydrogen is three times higher than that of gasoline products, so solid-state hydrogen storage is advantageous. Metal-organic frameworks (MOFs), multi-walled carbon nanotubes (MWCNTs) and graphene are solid adsorbents majorly employed for efficient H2 storage. The prominent features of MOFs such as permanent porosity, structural rigidity, and surface area are attractive and ideal for hydrogen storage. In addition, nanostructured carbon materials (MWCNTs and graphene) and their composites have demonstrated significant hydrogen storage capacities. Some important parameters for the success of the hydrogen economy include high storage density, adsorption/desorption temperature and cycling time. Cryo-hydrogen storage was achieved in MOFs and their composites with carbon structures, but storage at ambient temperature and acceptable pressures is a major hurdle. This review discusses various strategies and mechanisms in the design of adsorbents explored to improve H2 storage capacities and afford opportunities to develop new sustainable hydrogen technologies to meet energy targets. © 2018 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences

Existing technologies, such as storage of hydrogen in compressed and liquefied forms are not adequate to meet the broad on-board applications. Metal-organic frameworks (MOFs), multi-walled carbon nanotubes (MWCNTs) and graphene are solid adsorbents majorly employed for efficient H2 storage.

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Abstract: This paper deals with hydrogen storage properties of Ti-V based BCC solid solution incorporated with Fe. The alloy with composition Ti2FeV was prepared by arc melting method. X-ray diffraction (XRD) and energy dispersive X-ray analysis studies confirmed formation of solid solution phase with uniform composition and BCC structure. SEM studies revealed the formation of irregular shaped particles with size in the range of few microns up on hydrogenation of the parent alloy. The alloy shows maximum hydrogen storage capacity of 3.41 wt.% at 20 bar and 303 K and the thermodynamic parameters established near room temperature suitability of the alloy for solid state hydrogen storage applications. Hydrogenation kinetics is found to be quite fast and detailed kinetic analysis were done to underscore the hydrogenation mechanism. Activation energy during the initial stage of hydrogenation is found to be 30.8 kJ/mol. The value decreases to 14.4 kJ/mol for extended duration of hydrogenation, and this is explained based on difference in rate determining steps existing at different time scales. Graphic abstract: Extent of hydrogen absorption as a function of temperature and time for Ti2FeV alloy.[Figure not available: see fulltext.] © 2019, Indian Academy of Sciences.

Activation energy during the initial stage of hydrogenation is found to be 30.8 kJ/mol. The value decreases to 14.4 kJ/mol for extended duration of hydrogenation, and this is explained based on difference in rate determining steps existing at different time scales.

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A novel solid-solution MXene (Ti0.5V0.5)3C2 is successfully synthesized by exfoliating a solid-solution MAX phase (Ti0.5V0.5)3AlC2, and its catalytic effect on the hydrogen storage reaction of Mg is systemically evaluated for the first time. Typical layer morphology is observed for the prepared (Ti0.5V0.5)3C2, which exhibits a better catalytic activity than that of Ti3C2. The addition of 10 wt% (Ti0.5V0.5)3C2 remarkably reduces the dehydrogenation onset temperature of MgH2 by 70 °C, from 266 to 196 °C. At 250 °C, approximately 5.0 wt% H2 is released from the 10 wt% (Ti0.5V0.5)3C2-containing MgH2 within 20 min. The dehydrogenated sample rapidly absorbs 4.8 wt% H2 within 5 s at 120 °C; these hydrogenation kinetics are much more superior even to the well-studied Nb2O5 catalyst. The apparent activation energy is calculated to be 77.3 kJ/mol for the MgH2-10 wt% (Ti0.5V0.5)3C2 sample, which is only around half of that of the pristine MgH2 (153.8 kJ/mol). This is responsible for the remarkably reduced dehydrogenation operating temperature. Moreover, the chemical states of (Ti0.5V0.5)3C2 during dehydrogenation are also analysed and discussed. © 2018 Acta Materialia Inc.

A novel solid-solution MXene (Ti0.5V0.5)3C2 is successfully synthesized by exfoliating a solid-solution MAX phase (Ti0.5V0.5)3AlC2, and its catalytic effect on the hydrogen storage reaction of Mg is systemically evaluated for the first time. Typical layer morphology is observed for the prepared (Ti0.5V0.5)3C2, which exhibits a better catalytic activity than that of Ti3C2.

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Two approaches of engineering surface structures of V-Ti-based solid solution hydrogen storage alloys are presented, which enable improved tolerance toward gaseous oxygen (O2) impurities in hydrogen (H2) gas. Surface modification is achieved through engineering lanthanum (La)- or nickel (Ni)-rich surface layers with enhanced cyclic stability in an H2/O2 mixture. The formation of a Ni-rich surface layer does not improve the cycling stability in H2/O2 mixtures. Mischmetal (Mm, a mixture of La and Ce) agglomerates are observed within the bulk and surface of the alloy when small amounts of this material are added during arc melting synthesis. These agglomerates provide hydrogen-transparent diffusion pathways into the bulk of the V-Ti-Cr-Fe hydrogen storage alloy when the remaining oxidized surface is already nontransparent for hydrogen. Thus, the cycling stability of the alloy is improved in an O2-containing hydrogen environment as compared to the same alloy without addition of Mm. The obtained surface-engineered storage material still absorbs hydrogen after 20 cycles in a hydrogen-oxygen mixture, while the original material is already deactivated after 4 cycles. © 2017 American Chemical Society.

Two approaches of engineering surface structures of V-Ti-based solid solution hydrogen storage alloys are presented, which enable improved tolerance toward gaseous oxygen (O2) impurities in hydrogen (H2) gas. The obtained surface-engineered storage material still absorbs hydrogen after 20 cycles in a hydrogen-oxygen mixture, while the original material is already deactivated after 4 cycles.

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Magnesium borohydride (Mg(BH4)2) is a promising material for solid state hydrogen storage. However, the predicted reversible hydrogen sorption properties at moderate temperatures have not been reached due to sluggish hydrogen sorption kinetics. Hydrogen (H) → deuterium (D) exchange experiments can contribute to the understanding of the stability of the BH4 - anion. Pure γ-Mg(BH4)2, ball milled Mg(BH4)2 and composites with the additives nickel triboride (Ni3B) and diniobium pentaoxide (Nb2O5) have been investigated. In situ Raman analysis demonstrated that in pure γ-Mg(BH4)2 the isotopic exchange reaction during continuous heating started at ∼80 °C, while the ball milled sample did not show any exchange at 3 bar D2. However, during ex situ exchange reactions investigated by infrared (IR) and thermogravimetric (TG) analyses a comparable H → D exchange during long exposures (23 h) to deuterium atmosphere was observed for as received, ball milled and γ-Mg(BH4)2 + Nb2O5, while the Ni3B additive hindered isotopic exchange. The specific surface areas (SSA) were shown to be very different for as received γ-Mg(BH4)2, BET area = 900 m2 g-1, and ball milled Mg(BH4)2, BET area = 30 m2 g-1, respectively, and this explains why no gas-solid H(D) diffusion was observed for the ball milled (amorphous) Mg(BH4)2 during the short time frames of in situ Raman measurements. The heat treated ball milled sample partially regained the porous γ-Mg(BH4)2 structure (BET area = 560 m2 g-1). This in combination with the long reaction times allowing for the reaction to approach equilibrium explains the observed gas-solid H(D) diffusion during long exposure. We have also demonstrated that a small amount of D can be substituted in both high surface area and low surface area samples at room temperature proving that the B-H bonds in Mg(BH4)2 can be challenged at these mild conditions. © 2018 The Royal Society of Chemistry.

The specific surface areas (SSA) were shown to be very different for as received γ-Mg(BH4)2, BET area = 900 m2 g-1, and ball milled Mg(BH4)2, BET area = 30 m2 g-1, respectively, and this explains why no gas-solid H(D) diffusion was observed for the ball milled (amorphous) Mg(BH4)2 during the short time frames of in situ Raman measurements. We have also demonstrated that a small amount of D can be substituted in both high surface area and low surface area samples at room temperature proving that the B-H bonds in Mg(BH4)2 can be challenged at these mild conditions.

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Nowadays energy storage seems to be a vital point in any new energy paradigm. It has become an important and strategic issue, to ensure the energetic sufficiency of humanity. Indeed, hydrogen storage in solids has been proved and revealed as clean and efficient energy storage. Moreover, it can be thought as a seriously considered solution to enable renewable energy to be a part of our quotidian life. To achieve storing hydrogen in solid form, the present study aimed to concepts and simulates a solid-state hydrogen storage reactor (tank). An investigation of the parameters influencing the hydrogen storage performance is carried out. Meanwhile, to understand the physical phenomenon taking place during the storage of hydrogen, a 2D numerical modelling for a metal hydrides-based in hydrogen reactor is presented. A strong coupling between energy balance, kinetic law, as well as a mass momentum balance at sorbent bed temperature under a non-uniform pressure was resolved based on finite element method. The temporal evolutions of pressure, the raising temperature in the bed during the hydriding process as well as the impact of the hydrogen supply pressure within the tank are analysed and validated by comparison with the experimental work in literature, a good agreement is obtained. From an industrial point of view, this study can be used to design and manufacture an optimal solid-state hydrogen storage reactor. © EDP Sciences, 2019.

It has become an important and strategic issue, to ensure the energetic sufficiency of humanity. Meanwhile, to understand the physical phenomenon taking place during the storage of hydrogen, a 2D numerical modelling for a metal hydrides-based in hydrogen reactor is presented.

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Magnesium hydride has been seen as a potential material for solid state hydrogen storage, but the kinetics and thermodynamics obstacles have hindered its development and application. Three-dimensional flower-like TiO2@C and TiO2 were synthesized as the catalyst for MgH2 system and great catalytic activities are acquired in the hydrogen sorption properties. Experiments also show that the flower-like TiO2@C is superior to flower-like TiO2 in improving the hydrogen storage properties of MgH2. The hydrogen desorption onset and peak temperatures of flower-like TiO2 doped MgH2 is reduced to 199.2 °C and 245.4 °C, while the primitive MgH2 starts to release hydrogen at 294.6 °C and the rapid dehydrogenation temperature is even as high as 362.6 °C. The onset and peak temperatures of flower-like TiO2@C doped MgH2 are further reduced to 180.3 °C and 233.0 °C. The flower-like TiO2@C doped MgH2 composite can release 6.0 wt% hydrogen at 250 °C within 7 min, and 4.86 wt% hydrogen at 225 °C within 60 min, while flower-like TiO2 doped MgH2 can release 6.0 wt% hydrogen at 250 °C within 8 min, and 3.89 wt% hydrogen at 225 °C within 60 min. Hydrogen absorption kinetics is also improved dramatically. Moreover, compared with primitive MgH2 and the flower-like TiO2 doped MgH2, the activation energy of flower-like TiO2@C doped MgH2 is significantly decreased to 67.10 kJ/mol. All the improvement of hydrogen sorption properties can be ascribed to the flower-like structure and the two-phase coexistence of TiO2 and amorphous carbon. Such phase composition and unique structure are proved to be the critical factor to improve the hydrogen sorption properties of MgH2, which can be considered as the new prospect for improving the kinetics of light-metal hydrogen storage materials. © 2019

Magnesium hydride has been seen as a potential material for solid state hydrogen storage, but the kinetics and thermodynamics obstacles have hindered its development and application. Three-dimensional flower-like TiO2@C and TiO2 were synthesized as the catalyst for MgH2 system and great catalytic activities are acquired in the hydrogen sorption properties.

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Magnesium hydride (MgH 2 ) has been considered to be one of the most promising solid-state hydrogen storage materials owing to its high hydrogen capacities, excellent reversibility and abundant source. However, the high dehydrogenation energy barrier and poor kinetics embarrass the practical application of MgH 2 in fuel cell. Doping nano-catalyst is deemed to be the most effective method to improve kinetics property of hydrogen storage materials, but the nanoparticles generally suffer from agglomeration and inactivation during the cycling hydrogen storage. Here we present a promising strategy to facilely prepare a high-efficiency transition metal oxide nano-catalyst, TiO 2 nanoparticles, in which monodispersed single-crystal-like TiO 2 nanoparticles are wrapped with amorphous carbon. The in-situ synthesized TiO 2 nanoparticles/amorphous carbon catalyst exhibit superior catalytic effect on the dehydrogenation properties of MgH 2 . A significant reductions of hydrogen desorption temperature (163.5 °C) and activation energy (69.2 kJ mol −1 ) have been obtained for the TiO 2 nanoparticles/amorphous carbon catalyzed MgH 2 , which can be fully rehydrogenated with a reversible capacity of about 6.5 wt% at 200 °C within 5 min, and then completely dehydrogenated at 275 °C within 10 min. It is demonstrated that such significantly improved hydrogen desorption properties can be attributed to the in-situ formation of TiO 2 nanoparticles, amorphous carbon and multi-valance Ti species, which play the synergistically catalytic roles in the nano-catalyst. In particular, the presence of amorphous carbon in the catalyst can not only prevent the aggregation and growth of catalyst nanoparticles, but also dramatically reduce the desorption energy value of H in MgH 2 , according to the density functional theory calculation. This finding opens a new venue for the synthesis of monodispersed single-crystal-like TiO 2 nanoparticles/amorphous carbon catalyst with high-activity, safety, low cost, and its practical application in MgH 2 and other hydrogen storage systems. © 2019 Elsevier Ltd

A significant reductions of hydrogen desorption temperature (163.5 °C) and activation energy (69.2 kJ mol −1 ) have been obtained for the TiO 2 nanoparticles/amorphous carbon catalyzed MgH 2 , which can be fully rehydrogenated with a reversible capacity of about 6.5 wt% at 200 °C within 5 min, and then completely dehydrogenated at 275 °C within 10 min. This finding opens a new venue for the synthesis of monodispersed single-crystal-like TiO 2 nanoparticles/amorphous carbon catalyst with high-activity, safety, low cost, and its practical application in MgH 2 and other hydrogen storage systems.

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As an ideal secondary energy source, hydrogen energy has attracted the attention of researchers in the world in order to solve the problems of environment pollution and energy shortage. The solid-state hydrogen storage possessing high energy storage density and good safety is regarded as the most promising way among many hydrogen storage methods. Hydrogen storage materials composed of light elements (such as metal hydrides, borohydrides, aluminum hydrides, amino hydrides, ammonia borane) have become a research hotspot in the field of hydrogen storage owning to their high energy storage density. From the perspective of thermodynamics, this manuscript reviews recent progresses of several light hydrogen storage materials, especially the modification of materials. What's more, the development trend of light hydrogen storage materials is prospected. © 2019 Scientia Sinica Chimica. All rights reserved.

Hydrogen storage materials composed of light elements (such as metal hydrides, borohydrides, aluminum hydrides, amino hydrides, ammonia borane) have become a research hotspot in the field of hydrogen storage owning to their high energy storage density. What's more, the development trend of light hydrogen storage materials is prospected.

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MgH2 doped with transition metal halides (TiF4, NbF5, and ZrCl4) and activated carbon nanofibers (ACNF) for reversible hydrogen storage is prepared by ball milling technique. Transition metal halides provide catalytic effects for de/rehydrogenation kinetics, while ACNF benefits thermal conductivity and hydrogen permeability as well as prevents particle agglomeration during cycling. Significant reduction of onset and main dehydrogenation temperatures of MgH2 (ΔT = 243 and 158 °C, respectively) are achieved by doping with 5–10 wt % of NbF5, ACNF-TiF4 and ACNF-NbF5. During the 1st cycle, the latter samples liberate 4.7–5.0 wt % H2 within 1 h 30 min, whereas MgH2 doped with ACNF reaches only 1.5 wt % H2. The reaction between MgF2 and NbHx (x < 1) (MgH2-NbF5 and MgH2-ACNF-NbF5) during dehydrogenation results in the formation of new catalytic active species of Nb-F-Mg favoring kinetics. Upon four hydrogen release and uptake cycles, kinetics and reversibility within 1 h 30 min of MgH2-ACNF-NbF5 are preserved at 5.0 wt % H2, while those of MgH2-NbF5 and MgH2-ACNF-TiF4 decay to 4.4 wt % H2. Activation energy (EA) for dehydrogenation of MgH2 considerably decreases from 140.0 ± 10.2 to 37.8 ± 1.5 kJ/mol after doing with ACNF-NbF5. Superior performance of MgH2-ACNF-NbF5 to MgH2-NbF5 is due to synergistic effects of NbF5 and ACNF. In the case of MH2-ACNF-TiF4, the disappearance of active species benefiting kinetic properties and the formation of thermally stable TiH2 account for inferior hydrogen content reversible. © 2018 Elsevier Ltd

Transition metal halides provide catalytic effects for de/rehydrogenation kinetics, while ACNF benefits thermal conductivity and hydrogen permeability as well as prevents particle agglomeration during cycling. Activation energy (EA) for dehydrogenation of MgH2 considerably decreases from 140.0 ± 10.2 to 37.8 ± 1.5 kJ/mol after doing with ACNF-NbF5.

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Understanding diffusion of large solutes such as hydrogen and lithium in solids is of paramount importance for energy storage in metal hydrides and advanced batteries. Due to its high gravimetric and volumetric densities, magnesium is a material of great potential for solid-state hydrogen storage. However, the slow hydrogen diffusion kinetics and the deleterious blocking effect in magnesium have hampered its practical applications. Here, we demonstrate fast lateral hydrogen diffusion in quasifree magnesium films without the blocking effect. Massive concomitant lattice expansion leads to the formation of remarkable self-organized finger patterns extending over tens of micrometers. Detailed visualization of diffusion fronts reveals that the fingers in these patterns follow locally the direction of hydrogen diffusion. Thus, the streamlines of the diffusion process are self-recorded by means of the finger pattern. By inclusion of fast hydrogen diffusion objects or local gaps, the resulting streamlines exhibit a clear analogy to optical rays in geometric optics. The possibility to spatially manipulate hydrogen diffusion opens an avenue to build advanced hydrogen storage systems, cloaking and active plasmonic devices, as well as prototype systems for computational models. © 2018 American Physical Society.

Due to its high gravimetric and volumetric densities, magnesium is a material of great potential for solid-state hydrogen storage. By inclusion of fast hydrogen diffusion objects or local gaps, the resulting streamlines exhibit a clear analogy to optical rays in geometric optics.

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Ammonia is well-known as a hydrogen carrier owing to its high hydrogen capacity (17.8 wt %). However, the toxicity and the high storage pressure limit the application of ammonia. Consequently, storing ammonia in solid state has become the promising method to utilize ammonia for practical applications. In this review, ammonia absorption properties of metal hydrides, halides, and borohydrides to form metal amides and metal ammine complexes with various coordination numbers have been systematically summarized. Through this research, we found the correlation between the reactivity with ammonia and the Pauling electronegativity of neutral atoms according to different systems. Metal hydrides with small electronegativity value of the neutral atom of the cations can react with ammonia to form metal amides, which can be used as hydrogen storage material. For metal halides or borohydrides, the lower plateau pressure of ammonia absorption can be obtained in the material with larger electronegativity value of the neutral atom of cations. This useful tendency can be used in the materials design for the potential applications of ammonia-fed fuel cells. © 2018 American Chemical Society.

Metal hydrides with small electronegativity value of the neutral atom of the cations can react with ammonia to form metal amides, which can be used as hydrogen storage material. This useful tendency can be used in the materials design for the potential applications of ammonia-fed fuel cells.

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Firstly, the hydrogen storage materials for solid-state hydrogen storage are defined and summarized. Then, current research progress is summarized by comparing the mechanism, advantages and disadvantages of the hydrogen storage materials, and the future development trend of hydrogen storage materials is prospected. © 2019, China National Chemical Information Center. All right reserved.

Firstly, the hydrogen storage materials for solid-state hydrogen storage are defined and summarized. Then, current research progress is summarized by comparing the mechanism, advantages and disadvantages of the hydrogen storage materials, and the future development trend of hydrogen storage materials is prospected.

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Solid-state hydrogen storage is of considerable concern as a potential hydrogen source for portable fuel cell applications. This study mainly focuses on kinetics of NaBH4/Al2O3 nanoparticles (20 nm)/H2O system with CoCl2 as catalyst and the factors that affect the hydrogen generation rate (HGR). It is observed that the reaction rate increases considerably with increase in NaBH4, Al2O3 nanoparticle (20 nm), CoCl2 and NaOH concentrations and the respective reaction orders are calculated. Hydrogen generation rate is also investigated at different temperatures (303, 313, 323 and 333 K) for constant NaBH4 (1.25 moles/L), NaOH (1.4 moles/L), CoCl2 (0.02 moles/L) and Al2O3 (0.09 moles/L) concentrations. Kinetics of the NaBH4 hydrolysis reaction increases with ?-Al2O3 nanoparticles and the calculated activation energy is 29 kJ/moles. This study also reports that a combined dual-solid-fuel system is highly efficient in terms of hydrogen storage capacities compared with a single hydride based system. Maximum hydrogen generation efficiency, observed at a mass ratio of 0.09: 0.7 (Al2O3/NaBH4), is 99.34%. © 2019 Assoc. Brasiliera de Eng. Quimica / Braz. Soc. Chem. Eng.. All rights reserved.

This study also reports that a combined dual-solid-fuel system is highly efficient in terms of hydrogen storage capacities compared with a single hydride based system. Maximum hydrogen generation efficiency, observed at a mass ratio of 0.09: 0.7 (Al2O3/NaBH4), is 99.34%.

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In this study, a novel set of comprehensive arithmetic correlations has been proposed to design an industrial scale cylindrical reactor with embedded cooling tubes (ECT) for metal hydride (MH) based hydrogen storage and thermal management applications. Based on ASME standards, different nominal pipe sizes were imparted into a cylindrical reactor design with ECT to accommodate 50 kg of LaNi4.7Al0.3 alloy. A three dimensional numerical model has been developed using COMSOL Multiphysics 4.3a to predict the hydriding performance of designed reactors, which was further experimentally validated as well. At an absorption condition of 30 bar supply pressure and 298 K absorption temperature with 60 lpm volumetric HTF flow rate, 6 inch reactor with 99 ECT portrayed better heat transfer characteristics. From the parametric investigation, it is observed that the variation of supply pressure has predominant effect followed by the variation of the HTF flow rate on hydriding (absorption) kinetics of the device. However, the variation of absorption temperature has minuscule influence on the hydriding performance. At a supply condition of 30 bar and 298 K with water flow rate of 30 lpm, a hydrogen storage capacity (HSC) of 1.29 wt% was achieved within 2060 s. © 2019 Hydrogen Energy Publications LLC

In this study, a novel set of comprehensive arithmetic correlations has been proposed to design an industrial scale cylindrical reactor with embedded cooling tubes (ECT) for metal hydride (MH) based hydrogen storage and thermal management applications. A three dimensional numerical model has been developed using COMSOL Multiphysics 4.3a to predict the hydriding performance of designed reactors, which was further experimentally validated as well.

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Nanomaterials may help to solve issues such as water availability, clean energy generation, control of drug-resistant microorganisms and food safety. Here we review innovative approaches to solve these issues using nanotechnology. The major topics discussed are wastewater treatment using carbon-based, metal-based and polymeric nanoadsorbents for removing organic and metal contaminants; nanophotocatalysis for microbial control; desalination of seawater using nanomembranes; energy conversion and storage using solar cells and hydrogen-sorbents nanostructures; antimicrobial properties of nanomaterials; smart delivery systems; biocompatible nanomaterials such as nanolignocellulosis and starches-based materials, and methods to decrease the toxicity of nanomaterials. Significantly, here it is reviewed two ways to palliate nanomaterials toxicity: (a) controlling physicochemical factors affecting this toxicity in order to dispose of more safe nanomaterials, and (b) harnessing greener synthesis of them to bring down the environmental impact of toxic reagents, wastes and byproducts. All these current challenges are reviewed at the present article in an effort to evaluate environmental implications of nanomaterials technology by means of a complete, reliable and critical vision. © 2017, Springer International Publishing AG.

Nanomaterials may help to solve issues such as water availability, clean energy generation, control of drug-resistant microorganisms and food safety. All these current challenges are reviewed at the present article in an effort to evaluate environmental implications of nanomaterials technology by means of a complete, reliable and critical vision.

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In an effort to realize a sustainable hydrogen economy, we are facing the demanding and challenging issue of providing compact and safe storage solutions for hydrogen in solid-state materials. Studies on the hydrogen storage properties of materials generally involve their phase structures, microstructures, thermal/structural stability, chemical compositions and bonding, which can be studied by ex situ experimental technologies. However, the experimental results obtained from ex situ measurements may be contaminated during sample handling, and some important intermediate phases are too metastable/unstable to be detected. To overcome the drawbacks, in situ studies are carried out, leading to a large number of unprecedented advantages. In this review, recent advances regarding in situ measurement technologies for solid-state hydrogen storage materials are summarized, mainly focusing on metal hydrides and complex hydrides. The working principles together with the devices used for the in situ methods are briefly introduced. Afterwards, both the classic and recent advances regarding the in situ measurement technologies for metal hydrides and complex hydrides are comprehensively summarized and reviewed. In addition to highlighting the tremendous merits of the in situ methods and the relevant achievements in the field of hydrogen storage materials, the remaining challenges and trends of the emerging research are also discussed. © 2020 Elsevier Ltd

In an effort to realize a sustainable hydrogen economy, we are facing the demanding and challenging issue of providing compact and safe storage solutions for hydrogen in solid-state materials. Studies on the hydrogen storage properties of materials generally involve their phase structures, microstructures, thermal/structural stability, chemical compositions and bonding, which can be studied by ex situ experimental technologies.

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Magnesium borohydride (Mg(BH4)2) is an attractive materials for solid-state hydrogen storage due to its high hydrogen content (14.9 wt%). In the present work, the dehydrogenation performance of Mg(BH4)2 by adding different amounts (10, 20, 40, 60 wt%) of two-dimensional layered Ti3C2 MXene is studied. The Mg(BH4)2-40 wt% Ti3C2 composite releases 7.5 wt% hydrogen at 260 °C, whereas the pristine Mg(BH4)2 only releases 2.9 wt% hydrogen under identical conditions, and the onset desorption temperature decreases from 210 °C to a relative lower temperature of 82 °C. The special layered structure of Ti3C2 MXene and fluorine plays an important role in dehydrogenation process especially at temperatures below 200 °C. The main dehydrogenation reaction is divided into two steps, and activation energy of the Mg(BH4)2-40 wt% Ti3C2 composite is 151.3 kJ mol−1 and 178.0 kJ mol−1, respectively, which is much lower than that of pure Mg(BH4)2. © 2020 Hydrogen Energy Publications LLC

The Mg(BH4)2-40 wt% Ti3C2 composite releases 7.5 wt% hydrogen at 260 °C, whereas the pristine Mg(BH4)2 only releases 2.9 wt% hydrogen under identical conditions, and the onset desorption temperature decreases from 210 °C to a relative lower temperature of 82 °C. The special layered structure of Ti3C2 MXene and fluorine plays an important role in dehydrogenation process especially at temperatures below 200 °C.

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A systematic calculation has been performed in order to study phase transitions and hydrogen storage properties of ternary hydride Li2MgH4 under pressure. The structural, elastic, electronic and vibrational properties of Li2MgH4 are collected by means of density functional theory. There are three phases identified; Pbam at 0 GPa, Pnma at 5 GPa and Pna21 at 65 GPa Pbam and Pnma phases of Li2MgH4 are found to be mechanically and dynamically stable. Ductility of the phases are determined based on Pugh's criteria. It is found that Li2MgH4 becomes ductile at 5 GPa, otherwise it is a brittle material. Electronic band structures and corresponding partial density of states of phases are also obtained. All phases at 0 GPa, 5 GPa and 65 GPa have wide band gaps, indicating that Li2MgH4 is an insulator at all pressures. The phonon dispersion curves of Pbam and Pnma phases have no imaginary frequency indicating that both phases of Li2MgH4 are dynamically stable. The gravimetric hydrogen density of Li2MgH4 is calculated as 10.52 wt %, which is a great rate along with the hydrogen desorption temperature of 670 K. © 2019 Hydrogen Energy Publications LLC

A systematic calculation has been performed in order to study phase transitions and hydrogen storage properties of ternary hydride Li2MgH4 under pressure. Ductility of the phases are determined based on Pugh's criteria.

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Hydrogen is an ideal candidate to fuel as “future energy needs”. Hydrogen is a light (Mw = 2.016 g mol−1), abundant, and nonpolluting gas. Hydrogen as a fuel can be a promising alternative to fossil fuels; i.e., it enables energy security and takes cares of climate change issue. Hydrogen has a low density of around 0.0899 kg m−3 at normal temperature, and pressure (~7% of the density of air), which is the main challenge in its real applications. It means, for example, 1 kg of hydrogen requires an extremely high volume of around 11 m3. In order to solve this limitation of hydrogen, solid-state hydrogen storage materials are used to store hydrogen efficiently and effectively. In this chapter, an attempt has been developed to provide a comprehensive overview of the recent advances in hydrogen storage materials in terms of capacity, content, efficiency, and mechanism of storage. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd 2020.

Hydrogen is an ideal candidate to fuel as “future energy needs”. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd 2020.

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The hydrogen economy is a proposed system where hydrogen is produced and used extensively as the primary energy carrier. Successful development of hydrogen economy means innumerable advantages for the environment, energy security, economy, and final users. One major key to wholly develop hydrogen economy is safe, compact, light and cost-efficient hydrogen storage. The conventional gaseous state storage system as pressurized hydrogen gas and liquid state storage system pose safety and cost problems to onboard applications; therefore, they do not satisfy the future goals for a hydrogen economy. Fortunately, solid-state storage systems based on metal hydrides have demonstrated great potentials to store hydrogen in large quantities in a quite secure, compact, and repeatedly reversible manner and thus, becoming increasingly attractive option for hydrogen applications. However, techno-economic feasibility of hydrogen storage systems is yet to be realized as none of the current metal hydrides fulfill all the essential criteria for a practical hydrogen economy, mainly because of low hydrogen storage capacity, sluggish kinetics and unacceptable temperatures of hydrogen absorption/desorption. This article gives a brief review of hydrogen as an ideal sustainable energy carrier for the future economy, its storage as the stumbling block as well as the current position of solid-state hydrogen storage in metal hydrides and makes a recommendation based on the most promising novel discoveries made in the field in recent times which suggests a prospective breakthrough towards a hydrogen economy. © 2019 Hydrogen Energy Publications LLC

The conventional gaseous state storage system as pressurized hydrogen gas and liquid state storage system pose safety and cost problems to onboard applications; therefore, they do not satisfy the future goals for a hydrogen economy. Fortunately, solid-state storage systems based on metal hydrides have demonstrated great potentials to store hydrogen in large quantities in a quite secure, compact, and repeatedly reversible manner and thus, becoming increasingly attractive option for hydrogen applications.

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Mg-based hydrogen storage materials are considered to be one of the most promising solid-state hydrogen storage materials due to their large hydrogen storage capacity and low cost. However, slow hydrogen absorption/desorption rate and excessive hydrogen absorption/desorption temperature limit the application of Mg-based hydrogen storage materials. The present paper reviews the advances in the research of Mg-based hydrogen storage film in recent years, including the advantage of the film, the function theory of fabricating method and its functional theory, and the influencing factors in the technological process. The research status worldwide is introduced in detail. By comparing pure Mg, Pd-caped Mg, non-palladium capped Mg, and Mg alloy hydrogen storage films, an ideal tendency for producing Mg-based film is pointed out, for example, looking for a cheap metal element to replace the high-priced Pd, compositing Mg film with other hydrogen storage alloy of catalytic elements, and so on. © 2019 Chinese Physical Society and IOP Publishing Ltd.

The research status worldwide is introduced in detail. By comparing pure Mg, Pd-caped Mg, non-palladium capped Mg, and Mg alloy hydrogen storage films, an ideal tendency for producing Mg-based film is pointed out, for example, looking for a cheap metal element to replace the high-priced Pd, compositing Mg film with other hydrogen storage alloy of catalytic elements, and so on.

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Given the fact that lithium aluminum hydride (LiAlH4) can exist in distinct crystalline structures under different conditions, in this study, we aim to theoretically investigate the structural properties and the pressure-induced phase transformations of its 13 closely related crystal structures by means of the density functional theory (DFT). The present study reveals that the phase transformation of LiAlH4 from the most stable form (α-phase) to the second most stable form (-phase) occurs at approximately 3.3 GPa, corresponding to a volume collapse of ∼14% and a reduction of 22% in the crystal volume. Due to the relatively higher hydrogen weight content, -LiAlH4 becomes a potentially attractive candidate for solid-state hydrogen storage at moderate pressures. The two most stable forms, i.e., the structures with the (i) P21/c (α-LiAlH4) and (ii) I41/a (-LiAlH4) space groups, have been selected so that their structural and electronic properties can be discussed in greater detail. Our study also shows that the numerical results are greatly influenced by the choice of the DFT methods used, such as the exchange-correlation functionals and optimization schemes. © 2020 Author(s).

Given the fact that lithium aluminum hydride (LiAlH4) can exist in distinct crystalline structures under different conditions, in this study, we aim to theoretically investigate the structural properties and the pressure-induced phase transformations of its 13 closely related crystal structures by means of the density functional theory (DFT). Due to the relatively higher hydrogen weight content, -LiAlH4 becomes a potentially attractive candidate for solid-state hydrogen storage at moderate pressures.

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Zr(BH4)4·8NH3 is considered to be a promising solid state hydrogen-storage material, due to its high hydrogen capacity and low dehydrogenation temperature. However, the possible applications of Zr(BH4)4·8NH3 have been greatly hampered by the complicated and less applicable synthesis process, which must be operated at relatively low temperature (<20 °C). Herein, we reported a simple and facile “heating-(ball milling) BM vial” method via physical vapour deposition to tackle this issue. By this technique, Zr(BH4)4·8NH3 was successfully synthesized. Furthermore, composite formation by adding 10 wt% NaBH4 to the as-prepared Zr(BH4)4·8NH3 was found to be able to lower down the dehydrogenation peak of Zr(BH4)4·8NH3 from 130 to 75 °C and more excitingly, the possible emission of B2H6 and NH3 from dehydrogenation of only Zr(BH4)4·8NH3 was completely suppressed after addition of NaBH4. This research presents a new hydrogen-storage system based on Zr(BH4)4·8NH3+NaBH4 composite and it also implies a new development methodology of future hydrogen storage materials. © 2018 Hydrogen Energy Publications LLC

However, the possible applications of Zr(BH4)4·8NH3 have been greatly hampered by the complicated and less applicable synthesis process, which must be operated at relatively low temperature (<20 °C). Herein, we reported a simple and facile “heating-(ball milling) BM vial” method via physical vapour deposition to tackle this issue.

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Hydrogen storage materials based on the stoichiometry Mg(Ni1-xMnx)2 have been synthesized by High Energy Ball Milling (HEBM) and studied as potential candidate materials for solid state hydrogen storage. The microstructures of the as-cast and the milled alloys were characterized by means of X-ray Powder Diffraction (XRD) and Scanning Electron Microscopy (SEM) both prior and after the hydrogenation process. The storage characteristics (Pressure-Composition-Temperature isotherms) and the sorption kinetics obtained by a commercial and automatically controlled Sievert-type apparatus. The X-ray results showed that the substitution of Mn over Ni could eliminate and inhibit the MgNi2 phase. The calculation of the average crystallite size showed that the increase of the amount of Mn can reduce the size at the early stages, but for Mn content higher than 0.25 the crystallite size increases, while the microstrain levels decreased monotonically. The hydrogenation and dehydrogenation measurements took place at several temperatures (150–200–250–300 °C). The results showed that the kinetics for both the hydrogenation and dehydrogenation can be fast for operation at temperatures between 250 and 300 °C, but for temperatures below 200 °C the hydrogenation process is very slow, and the dehydrogenation process cannot be achieved. © 2019 Elsevier Ltd

Hydrogen storage materials based on the stoichiometry Mg(Ni1-xMnx)2 have been synthesized by High Energy Ball Milling (HEBM) and studied as potential candidate materials for solid state hydrogen storage. The hydrogenation and dehydrogenation measurements took place at several temperatures (150–200–250–300 °C).

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NaMgH3 has been considered to be a potential candidate for solid-state hydrogen storage due to its considerable hydrogen gravimetric (6.0 wt %) and volumetric (88.0 g/L) densities. Meanwhile, NaMgH3 possesses an outstanding theoretical thermal storage density of 2881 kJ/kg, which makes it one of the most promising thermal energy storage materials. However, the sluggish dehydrogenation kinetics of NaMgH3 embarrasses further practical application. Doping a nanosize Ti-based catalyst is treated to be one of the most effective methods to settle the poor dehydriding kinetics. In this work, different kinds of TiO2 catalysts, the 5 wt % TiO2 microparticle (MP) (100 nm), TiO2 nanoparticle (NP) (5-10 nm), and TiO2 nanotube (NT) (5-10 nm), were doped into NaMgH3 in the process of ball milling and heat treatment, which in situ formed Na0.46TiO2 significantly promoting the full hydrogen desorption kinetics of NaMgH3. Among all samples, the TiO2 NT-doped sample shows the best performance of which the onset decomposition temperature is reduced to 300 °C, and the first- and second-step decomposition peak temperatures are decreased to 346.3 and 355.8 °C, respectively. The TiO2 NT-doped sample desorbs approximately 3.4 wt % H2 at 350 °C within 10 min, while the pure NaMgH3 sample releases only 0.2 wt % H2 in 10 min. The significant improvement in both two decomposition reactions kinetics of NaMgH3 can be attributed to the tubular morphology of the TiO2 NT and the in situ formation of multivalence Ti species (Na0.46TiO2). These two reasons can change the kinetic models of NaMgH3 from A2 to R2 and further dramatically decrease the activation energies of first- and second-step decomposition reactions of NaMgH3 to 91.7 and 142.1 kJ/mol, respectively. In particular, the in situ formed Na0.46TiO2 can benefit the e- transfers among Na+, Mg2+, and H-, tremendously enhancing dehydrogenation properties. © 2019 American Chemical Society.

However, the sluggish dehydrogenation kinetics of NaMgH3 embarrasses further practical application. In this work, different kinds of TiO2 catalysts, the 5 wt % TiO2 microparticle (MP) (100 nm), TiO2 nanoparticle (NP) (5-10 nm), and TiO2 nanotube (NT) (5-10 nm), were doped into NaMgH3 in the process of ball milling and heat treatment, which in situ formed Na0.46TiO2 significantly promoting the full hydrogen desorption kinetics of NaMgH3.

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A new and solvent-free synthesis route has been adopted and optimized to prepare crystalline VNbO5 from the mechanochemical reaction between Nb2O5 and V2O5 as starting reagents. The substantially amorphous mixture of equimolar pentoxide V and Nb metals observed after extended mechanical treatment transforms into a crystalline powder following calcination under mild conditions at 710 K. The structure solution of the X-ray diffraction pattern using a global optimization approach, combined with Rietveld refinement, points to a space group P212121 (no. 19) different from Pnma (no. 62) previously proposed in the literature assuming it to be isostructural to VTaO5. The new space group helps to describe weak peaks that remained previously unaccounted for and allows more reliable determination of atomic fractional coordinates and interatomic distance distribution. The as-prepared VNbO5 has been tested as a dopant (5 wt%) for the purpose of solid state hydrogen storage, decreasing significantly the release of hydrogen of MgH2/Mg (620 K) and further enhancing the hydrogen sorption kinetic properties. © The Royal Society of Chemistry 2019.

The substantially amorphous mixture of equimolar pentoxide V and Nb metals observed after extended mechanical treatment transforms into a crystalline powder following calcination under mild conditions at 710 K. The structure solution of the X-ray diffraction pattern using a global optimization approach, combined with Rietveld refinement, points to a space group P212121 (no. The new space group helps to describe weak peaks that remained previously unaccounted for and allows more reliable determination of atomic fractional coordinates and interatomic distance distribution.

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A holistic approach is required for the development of materials and systems for hydrogen storage, embracing all the different steps involved in a successful advance of the technology. The several engineering solutions presented in this work try to address the technical challenges in synthesis and application of solid-state hydrogen storage materials, mainly metal hydride based compounds. Moving from the synthesis of samples in lab-scale to the production of industrial sized batches a novel process development is required, including safety approaches (for hazardous powders), and methods to prevent the contamination of sensitive chemicals. The reduction of overall costs has to be addressed as well, considering new sources for raw materials and more cost-efficient catalysts. The properties of the material itself influence the performances of the hydride in a pilot storage tank, but the characteristics of the system itself are crucial to investigate the reaction limiting steps and overcome hindrances. For this, critical experiments using test tanks are needed, learning how to avoid issues as material segregation or temperature gradients, and optimizing the design in the aspects of geometry, hull material, and test station facilities. The following step is a useful integration of the hydrogen storage system into real applications, with other components like fuel cells or hydrogen generators: these challenging scenarios provide insights to design new experiments and allow stimulating demonstrations. © 2018 Trans Tech Publications, Switzerland.

The reduction of overall costs has to be addressed as well, considering new sources for raw materials and more cost-efficient catalysts. The following step is a useful integration of the hydrogen storage system into real applications, with other components like fuel cells or hydrogen generators: these challenging scenarios provide insights to design new experiments and allow stimulating demonstrations.

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Hydrogen energy is one of the most important choices for realizing clean energy because of its wide sources, no pollution, and high energy density. The technological innovation of fuel cells contributes to the attractive prospect of hydrogen energy in vehicles, but the problem of hydrogen filling and hydrogen storage has become one of the obstacles to the development of hydrogen energy cars. The safe and efficient hydrogen storage is crucial for the large-scale application of hydrogen energy. Till now there have been developed three main hydrogen storage methods, which include high-pressure gaseous hydrogen storage, low-temperature liquid hydrogen storage and solid-state hydrogen storage. The gravimetric density of gaseous hydrogen storage system can be promoted by increasing the pressure of hydrogen and the specific strength of container material. However, H2 molecular interaction causes a relatively low volumetric density of gaseous hydrogen storage system, and excessively high hydrogen pressure challenges the safety and heightens design difficulty and cost of hydrogen tanks. The liquid hydrogen storage owns ideal gravimetric and volumetric density, which can be realized by compres-sing and liquefying hydrogen gas. However, liquid hydrogen is particularly prone to volatilize and liquid hydrogen container requires strict storing conditions. In addition, the liquefying process of gaseous hydrogen is uneconomical, as it consumes an energy quantity that constitutes about 40% of the combustion heat release of the stored hydrogen. For the solid-state hydrogen storage, hydrogen is stored in the hydrides in the form of atom or ion. Hence, the solid-state hydrogen storage obtains an impressively high volumetric density and enjoys greater security because the hydrogen storage materials absorb/desorb hydrogen at mild conditions. But the gravimetric density of hydrogen storage materials is comparatively low. The high-pressure hybrid hydrogen storage vessel, which combines the advantages of gaseous and solid-state hydrogen storage methods, offers a feasible path to safe and high-density hydrogen storage. The volumetric density of high-pressure hydrogen tank can be effectively enhanced by the hydrogen storage materials, resulting in lower operating pressure, smaller volume, and higher safety. The performance promotion of the high-pressure hybrid hydrogen storage vessels depends upon the development of materials with excellent hydrogen sorption performances under high hydrogen pressure. The AB2 type ZrFe2-based and TiCr2 based alloys are the currently prevailing high-pressure hydrogen storage materials. Though researchers mainly concentrate on and have achieved the regulation of storage capacity, absorption/desorption pressure plateau and kinetics through the alloying trials which partially substitute elements with various atomic radius and electronic structures for either A-site or B-site, the gravimetric densities of ZrFe2-based and TiCr2-based alloys are still unsatisfactory. NaAlH4 and AlH3 display considerable potential as candidate storage materials owing to their intrinsically high storage density. For NaAlH4, sufficient works have preliminarily confirmed the effectiveness of nanosizing and catalyst-doping toward dehydrogenation temperature reduction and cyclic stability enhancement. And the yield of AlH3 along with its crystallinity can likely be enhanced by adopting ball milling or improving the solvent. This review starts with a brief introduction of how the high-pressure hybrid hydrogen storage vessel works and a summary of the performance requirements of the hydrogen storage materials. It then provides detailed discussion and description upon the structure, characteristics and research status quo with respect to the above-mentioned two species of high-pressure hydrogen storage materials, i.e.hydrogen storage alloys (ZrFe2, TiCr2) and aluminum based complex hydrides (NaAlH4, AlH3). © 2019, Materials Review Magazine. All right reserved.

But the gravimetric density of hydrogen storage materials is comparatively low. The volumetric density of high-pressure hydrogen tank can be effectively enhanced by the hydrogen storage materials, resulting in lower operating pressure, smaller volume, and higher safety.

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In solid-state hydrogen storage in light metal hydrides, nanoconfinement and the use of catalysts represent promising solutions to overcoming limitations such as poor reversibility and slow kinetics. In this work, the morphology and hydrogen desorption kinetics of NaAlH4 melt-infiltrated into a previously developed Ti-based doped porous Al scaffold is analysed. Small-angle X-ray scattering and scanning electron microscopy analysis of low NaAlH4 loading in the porous Al scaffold has revealed that mesopores and small macropores are filled first, leaving the larger macropores/voids empty. Temperature-programmed desorption experiments have shown that NaAlH4-infiltrated porous Al scaffolds show a higher relative H2 release, with respect to NaAlH4 + TiCl3, in the temperature range 148–220 °C, with the temperature of H2 desorption trending to bulk NaAlH4 with increasing scaffold loading. The Ti-based catalytic effect is reproduced when the dopant is present in the scaffold. Further work is required to increase the mesoporous volume in order to enhance the nanoconfinement effect. © 2018 Hydrogen Energy Publications LLC

In this work, the morphology and hydrogen desorption kinetics of NaAlH4 melt-infiltrated into a previously developed Ti-based doped porous Al scaffold is analysed. Small-angle X-ray scattering and scanning electron microscopy analysis of low NaAlH4 loading in the porous Al scaffold has revealed that mesopores and small macropores are filled first, leaving the larger macropores/voids empty.

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