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Magnesium hydride solids doped with transition metals have received attention recently as prospective hydrogen storage materials for a green energy source and a hydrogen economy. In this study, MgTiHn (n = 1–20) clusters were investigated for the first time by employing the B3PW91 hybrid density functional theory computational chemistry technique with all electron basis sets to determine precise cluster structures and the maximum hydrogen capacity for this model system. We find that hydrogen atoms bind to the metal cluster core until a MgTiH14 saturation limit is reached, with hydrogen dissociation from this system occurring for MgTiH15 and larger cluster sizes. This MgTiH14 cluster contains a large 16.4% hydrogen by mass. This saturation size limit and hydrogen mass percent is larger than the analogous MgScHn system previously reported. The clusters relative stabilities and electronic properties are discussed along with a possible novel hydrogen dissociation pathway. MgTiH10 and MgTiH13 clusters are predicted to be especially stable species in this size range. [ABSTRACT FROM AUTHOR]

The potential for decorating single Li, Na, or K atoms onto BeS monolayers and their subsequent hydrogen storage performance were investigated using first-principle density functional theory (DFT) calculations. The single-atom Li, Na, or K exhibited strong adhesion to the BeS monolayer, with binding energies of −2.662 eV, −1.982 eV, or −1.669 eV, respectively. Each Li or Na atom on BeS demonstrated the ability to capture four H 2 molecules, while a single K atom could bind only three H 2 molecules. Notably, Li exhibited stronger binding with stored H 2 compared to Na or K. Moreover, by increasing the number of Li atoms on each side of the BeS monolayer to nine, the storage of H 2 molecules was improved to a total of 54, concomitant with an advantageous average adsorption energy of −0.236 eV. This enhancement resulted in a significant increase in the hydrogen storage capacity to 6.514 wt%. Molecular dynamics simulations indicated a desorption temperature of approximately 450 K, with the 18 Li atoms remaining strongly bonded to the BeS due to their high diffusion energy of 0.578 eV. Thus, the Li-decorated BeS monolayer emerges as a promising substrate for achieving exceptional and reversible hydrogen storage performance. • Alkali-metal atom (Li, Na, or K) could be well dispersed on the BeS monolayer. • Li atom shows a stronger adsorption strength to H 2 molecules than Na or K. • 18 Li atoms on BeS can capture 54H 2 with an ideal E adsav of −0.236 eV. • Li atoms remain dispersed on BeS even at desorption temperature of the 54H 2. • Li-decorated BeS demonstrates a high hydrogen storage capacity of 6.514 wt%. [ABSTRACT FROM AUTHOR]

Metal hydride storage system (MHSS) has been widely used mostly because of its large storage capacity and high degree of safety. The improvement of the heat transfer performance is one of possible techniques to enhance the overall MHSS performance. The well arrangement of the heat exchanger structure from a semi-cylindrical coil heat exchanger with central return tube (SCHE-CR) significantly reduces the hydrogen absorption duration. However, the modelling of the thermal behaviour for the SCHE-CR during desorption process is missing in the literature. Therefore, this study aims to develop a model for both hydrogen absorption and desorption processes and analyse the thermal performance during the cycle. Phase change material (PCM) is incorporated with the heat exchanger for further improvement of the MHSS performance. The storage is designed under three different PCM configurations, including PCM jacket, pool bed, and capsule. The numerical results report that the duration of the absorption-desorption cycle is reduced by over 50% when using SCHE-CR instead of a helical coil. The PCM configurations, especially the PCM capsule, increase the MHSS performance, especially during the absorption. The duration of one cycle is decreased by at least 39% when combining the SCHE-CR with PCM. The HTF temperature significantly affects the MHSS performance, especially during the desorption. Reduction in HTF temperature reduces the absorption duration by at least 15%, while increasing the HTF temperature reduces the desorption duration by at least 25%. The new MHSS configuration would be beneficial to enhance the heat exchange during the absorption-desorption cycle of industrial MHSS applications. • A novel method for faster hydrogen storage. • 31% reduction of duration for one complete cycle. • PCM capsule improved hydrogen charging and discharging time. • 39% reduction of complete cycle, using capsule PCM. • Significant reduction of hydrogen desorption, under fluid temperature. [ABSTRACT FROM AUTHOR]

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

Structure and hydrogen storage properties of three Ti 31 V 26 Nb 26 Zr 12 M 5 multicomponent alloys with M = Fe, Co and Ni are investigated. The alloys synthesized by arc melting are characterized via X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The as-cast ingots present multi-phase dendritic structures composed mainly of BCC phases and small amounts of C14 Laves phases. Upon hydrogenation, each alloy absorbs around 1.9 H/M (number of hydrogen atoms per metal atoms) at room temperature. XRD of fully hydrogenated samples shows the formation of multi-phase structures composed of FCC and C14 hydrides. Thermo Desorption Spectroscopy (TDS) shows that the hydrogenated alloys present multi-step desorption processes with wide temperature ranges and low onset temperatures. XRD of partially hydrogenated samples indicate the presence of intermediate BCC hydrides. XRD of desorbed samples suggest reversible reactions of absorption/desorption: BCC + C14 alloy ↔ intermediate BCC hydride + C14 hydride ↔ FCC + C14 hydrides. • Ti 31 V 26 Nb 26 Zr 12 M 5 (M = Fe, Co, or Ni) multicomponent alloys were synthesized. • The alloys presented multi-phase structures composed of BCC and Laves C14 phases. • Fully hydrogenated samples formed multi-phase structures (FCC + C14 hydrides). • Partially hydrogenated samples showed the formation of intermediate BCC hydrides. • Desorbed samples suggest reversible multi-step processes of absorption/desorption. [ABSTRACT FROM AUTHOR]

Sustainable development of hydrogen energy is a prime concern to address the rising energy demand and the global energy problem since the hydrogen economy is reliable for clean and carbon-free energy carriers. Despite well-established commercial sector technologies, boil-off losses, explosive nature, and leakage risk still exist with compressed and liquefied storage. One of the significant remedies, solid-state hydrogen storage, improves bulk density and gravimetric capacity and addresses safety concerns. The rising popularity of light and heavy fuel cell vehicles is projected to promote the advancement of onboard solid-state hydrogen technology. The present review focuses on the importance of existing porous materials, polymers, metal, and complex metal hydrides for solid-state hydrogen storage and the dominance of Si nanostructures (SiNSs). The fabrication techniques of porous silicon, porous silicon nanowires, and Si quantum dots are accentuated. The review provides insights into the hydrogen-assisted properties, regularities, the importance of hydrogen energy on automobiles for alleviating climate change phenomena, and the application of SiNSs for hydrogen storage with other transition and alkali earth materials to overcome the issues. It highlights the importance of catalysts in resolving the existing reversibility and desorption issues associated with hydrogen energy storage. Different popular desorption techniques considering the pore dimensions are discussed. The evaluation may enable energy providers and Si-based fuel cells to be better customized, promoting the development of the hydrogen energy economy. • Solid-state H 2 storage overcomes the low energy storage density and safety issues. • High surface area of Silicon nanostructures facilitates atomic hydrogen storage. • Doping and alloying are possible techniques to enhance H 2 affinity at adsorbents. • Synergetic effect of PS and carbon nanostructures enhances storage capacity. • Water-based desorption is efficient, cost-effective, and low energy consumer. [ABSTRACT FROM AUTHOR]

To investigate the influence of thermal effects on the hydrogen desorption performance of the metal hydride hydrogen storage system, a two-dimensional numerical model was established based on a small metal hydride hydrogen storage tank, and its accuracy was verified by the temperature variations in the reaction zone of the hydrogen storage tank during hydrogen desorption. In addition, the influence of the heat transfer medium on the heat and mass transfer performance of the hydrogen desorption reaction was analyzed. An external heat transfer bath was added to simulate the thermal effect of the model during the hydrogen desorption reaction. The temperature and type of heat transfer medium in the heat transfer bath were modified, and the temperature and reaction fraction variations in each zone of the hydrogen storage model were analyzed. The results showed that under heat transfer water flow, the reaction rate in the center region of the hydrogen storage tank was gradually lower than that in the wall region. The higher the temperature of water flow, the shorter the total time required for the hydrogen desorption reaction and the shortening amplitude is reduced. The variations in the temperature and hydrogen storage capacity during hydrogen desorption were similar, with water and oil as the heat transfer medium, under the same flow rate and heat transfer temperature, however, the heat transfer time and hydrogen desorption time of water were about 10% and 5% shorter than that of oil, respectively. When the air was used as the heat transfer medium, the heat transfer rate of the air convection in the channel was lower than the heat transfer rate of the tank wall, reducing the temperature difference between the air and alloy on both sides of the wall, decreasing heat transfer efficiency, and significantly prolonging the time required for hydrogen desorption. [ABSTRACT FROM AUTHOR]

Hydrogen remains an attractive energy carrier because it is abundant, environmentally friendly and has the highest gravimetric energy density of any known substance. Despite this high gravimetric energy density, hydrogen suffers from a low volumetric energy density as a room-temperature gas. To maximize volumetric energy density, storing hydrogen as a magnesium hydride is an efficient and economically viable route, owing to the low weight and high earth abundance of magnesium. A long-lasting obstacle for using magnesium is the high temperature required to release hydrogen once absorbed by magnesium. Although nanoscale magnesium is known to have a favorable effect on the hydrogen desorption temperature, it is not sufficient. In this work, hydrogen absorption and release was investigated by measuring optical changes, which correspond to certain hydrogen concentrations in magnesium nanoparticles. Remarkably, hydrogen desorption from the magnesium nanoparticle assembled thin films at room temperature could be achieved by illumination. This photo-stimulated hydrogen desorption introduces an effective and simple method to enable reversible hydrogen storage in magnesium. The sensitivity of the optical method here used is demonstrated by the fact that even hydrogen absorption from ambient air at 1 ppm has been measured. This work demonstrates that hydrogen can be efficiently stored and released from magnesium nanoparticles using only photons. • Formation of small magnesium nanoparticles with gas aggregation nanoparticle source. • Hydrogenation of magnesium nanoparticles and visualisation of the process. • Photo-stimulated hydrogen desorption. • Hydrogen detection from ambient. [ABSTRACT FROM AUTHOR]

Using metal hydride for hydrogen storage in stationary applications and for transportation is a promising technology due to its advantages of large hydrogen storage capacity, low pressure and low energy consumption. Combining the metal hydride reactor with PCM is expected to recover the heat generated during the hydrogen absorption and use it for hydrogen desorption, thus improving the energy efficiency of the system. This paper proposes a metal hydride reactor integrated with honeycomb fins and PCM to enhance heat transfer. Based on simulations, the results show that the achieved hydrogen storage capacity is 1.326 wt%, the gravimetric and volumetric storage densities are 0.411% and 14.76 kg of H 2 per m3, respectively, and the mean saturated rates are 1.222 × 10−3 g s−1 and 0.773 × 10−3 g s−1 for absorption and desorption processes. Compared with the reactor without fins, the mass and volume of the reactor using honeycomb fins are increased, resulting in a decrease in gravimetric and volumetric storage density, but a increase in reaction rate during hydrogen absorption and desorption processes. Based on this structure, we also propose a honeycomb fin reactor filled with sandwich PCM to further accelerate the heat transfer in the reaction process. Compare to the reactor with PCM only filled on the periphery of the honeycomb fins, the hydrogen absorption and desorption times are shortened by about 86.4% and 81.1%, respectively. In addition, different reactor structures are compared using multiple KPIs to provide relevant suggestions for the reactor optimization. The obtained research results can provide a reference for effective thermal management methods in MH storage systems. • A metal hydride reactor integrated with honeycomb fins and PCM was proposed. • The comparison of reactor without fins and the effects of fin size were studied. • The placement of PCM and MH was optimized. • Multiple KPIs were used to evaluate the hydrogen absorption and desorption processes. • The optimized reactor performed better than other forms of reactors. [ABSTRACT FROM AUTHOR]

Transition metal doped magnesium hydride solids are a leading candidate for hydrogen storage materials. In this investigation, MgScH n clusters (n = 1–20) are theoretically studied using density functional theory and Møller-Plesset perturbation theory. It is determined that hydrogen binds successively to the MgSc diatomic metal center up to MgScH 13 when the cluster becomes saturated at 15.9% hydrogen by mass. In contrast to earlier predictions, we shown that for MgScH 14 and larger clusters molecular hydrogen dissociates from the core cluster structure. A local minimum is observed on the potential energy surface for larger clusters where dissociated hydrogen interacts with a negatively charged hydride of the core cluster in a dipole-induced dipole intermolecular force, providing insight into the dissociation pathway in bulk magnesium hydride materials doped with transition metals. Analysis of the frontier orbitals and natural bonding analysis of these clusters support this logical dissociation pathway. • MgScH n clusters are studied with density functional theory and ab initio methods. • MgScH n structures are determined by unbiased global optimization procedures. • MgScH 13 (15.9% hydrogen by mass) is largest cluster without dissociated hydrogen. • Dissociating H 2 can have temporary dipole moments coordinating to anionic hydride. • Cluster HOMO primarily consists of a hydride s atomic orbital in Sc-Mg-H backbone. [ABSTRACT FROM AUTHOR]

Body-centered cubic (BCC) alloys are considered as promising materials for hydrogen storage with high theoretical storage capacity (H/M ratio of 2). Nonetheless, they often suffer from sluggish kinetics of hydrogen absorption and high hydrogen desorption temperature. Carbon materials are efficient hydrogenation catalysts, however, their influence on the hydrogen storage properties of BCC alloy has not been comprehensively studied. Therefore, in this paper, composites obtained by milling of carbon catalysts (carbon nanotubes, mesoporous carbon, carbon nanofibers, diamond powder, graphite, fullerene) and BCC alloy (Ti 1.5 V 0.5) were extensively studied in the non-hydrogenated and hydrogenated state. The structure and microstructure of the obtained materials were studied by scanning and transmission electron microscopes, X-ray diffraction (XRD), and Raman spectroscopy. XRD and Raman measurements showed that BCC alloy and carbon structures were in most cases intact after the composite synthesis. The hydrogenation/dehydrogenation studies showed that all of the used carbon catalysts significantly improve the hydrogenation kinetics, reduce the activation energy of the dehydrogenation process and decrease the dehydrogenation temperature (by nearly 100 K). The superior kinetic properties were measured for the composite with 5 wt % of fullerene that absorbs 3.3 wt % of hydrogen within 1 min at room temperature. [Display omitted] • Mechanical milling without milling balls prevents serious damage of carbon additives. • BCC alloy catalysed by fullerene absorbs 3.3 wt% of hydrogen within a minute. • The addition of carbon catalysts decreases the dehydrogenation temperature by 100 K. • The dehydrogenation process activation energy is twice reduced in studied composites. [ABSTRACT FROM AUTHOR]

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Aluminum hydride is particularly attractive as a hydrogen storage material due to its high hydrogen volumetric capacity and relatively low hydrogen desorption temperature. However, the properties of nanoscale α‑AlH3 particles are not studied completely due to the difficulties in their synthesis. In this work, we report the synthesis of nanoscale α-AlH3 based on a modified method, together with its activation energy measurements and hydrogen release kinetics. We have discovered that the dehydrogenation activation energy (93.23 kJ/mol) of nanoscale α-AlH3 is remarkably lower than that of micrometer-sized α-AlH3, which further expand practical application of AlH3. Moreover, we demonstrate that the decomposition kinetics of nanoscale α-AlH3 is controlled by nucleation and growth of the aluminum phase in three dimensions. This work first time provides systematic investigation of thermodynamic properties of nano-scale AlH3, which paves the way for its practical applications. [ABSTRACT FROM AUTHOR]

Abstract Using neutron reflectometry, we investigated the deuterium desorption of Pd-covered Ti films that have been deuterated at 1 bar deuterium at room temperature and then exposed to air. The deuterium content was monitored continuously for the first two days. Thereafter, measurements were conducted periodically, spanning a period of up to 2 years. The films were in the thickness range of 10–300 nm and the desorption behaviour showed a strong dependence on the film thickness. The smaller the Ti film thickness the faster the Ti films desorbed the stored deuterium. Graphical abstract Image 1 Highlights • Deuterium desorption in thin Pd-covered Ti films was monitored over 2 years • The thinner the Ti films, the faster they desorb the deuterium • After 2 years a 10 nm thick Ti film desorbed 80% of its originally stored deuterium • After 4 days the deuterium concentration follows an exponential decay [ABSTRACT FROM AUTHOR]

Abstract In order to improve the hydrogen storage capacity and cycle durability, hafnium (Hf) is used to partial substitute for Ti in Ti 23 V 40 Mn 37 alloy. Microstructure, hydrogen storage properties and their relationship have been investigated systematically. The results show that Ti 23- x Hf x V 40 Mn 37 (x = 0, 2 and 4) alloys are consisted of BCC and C14 Laves phases. With increasing of Hf content, the ratio of C14 Laves phase increases. The hydrogen desorption capacity of Hf substituted alloys is improved significantly, and it reaches the value of 1.88 wt% at 293 K when the composition is Ti 19 Hf 4 V 40 Mn 37. Effective hydrogen storage capacities decrease to 89.1% and 93.3% of their initial values after 20 cycles for 2 and 4 at.% Hf substituted alloys, respectively. The alloy with 4 at.% Hf substitution has the better cycle durability, which is caused by more V element solid solution in BCC phase. Highlights • Hf-substituted Ti V Mn alloy is reported the first time. • Hf partial substitution for Ti leads to more C14 Laves phase. • Hydrogen desorption capacity is increased significantly by Hf substitution. • Hf substitution of 4 at.% is preferable for higher cycle durability. [ABSTRACT FROM AUTHOR]

A two-dimensional axisymmetric model is developed to study the hydrogen desorption reaction and its subsequent discharge in a metal hydride canister. Experimental tests are performed on an in-house fabricated setup. An extensive study on the effects of the metal properties and boundary conditions on discharging performance is carried out through non-destructive testing (NDT). Results show that the desorption process is more effective if the activation energy for desorption ( E d ) and the reaction enthalpy ( ΔH ) decrease, and when the desorption rate coefficient ( C d ) and the external convection heat transfer coefficient when the bottle is being heated ( h ) increase. Furthermore, porosity ( ε ) can be useful for the design of hydrogen storage systems, with a trade-off between charge/discharge time and storage capacity. Numerical and experimental results are compared achieving a good agreement. These results can be used to select metal hydride materials and also for the future evaluation of metal hydride degradation. [ABSTRACT FROM AUTHOR]

Doping of MgH 2 with transition metals and their oxides is well-known procedure to improve its hydrogen (de)sorption properties, namely to lower the temperature of desorption and to achieve the kinetics speedup. In order to assess the influence Ti and TiO 2 doping has on H mobility and to characterize structurally and electronically observed differences, MgH 2 Mg interface doped with both Ti and TiO 2 have been studied using ab-initio interface molecular dynamics and bulk calculations. Results suggest different mechanisms of MgH 2 structure destabilization. The presence of dopants significantly stabilize MgH 2 Mg interface, which is confirmed by work of adhesion computation. Calculated formation energies show that interface system with doped TiO 2 is more stable. In terms of H mobility, molecular dynamics simulations confirm that Ti doping is more effective than TiO 2 in lowering the desorption temperature. The mobility of hydrogen atoms close to dopant is much higher in the case of Ti than in the case of TiO 2 . Electronic structure characterization reveals that oxygen atoms with high electron affinity forms more pronounced ionic bonding with Ti and the other neighbor Mg atoms. This in turn cause a shorter Ti H bonds in first coordination than in the case of Ti doping and further reduction of H atoms mobility. This is in accordance with molecular dynamics predictions. [ABSTRACT FROM AUTHOR]

A numerical study is conducted to investigate the influence of additional components – a heat-fin and metal-foam – on the hydrogen discharging performance of metal hydride beds. First, a three-dimensional, transient hydrogen desorption model developed in our previous works is applied to two different experimental metal hydride beds (MHBs): one with a heat-fin and the other with metal-foam. Then, the simulation results are compared with the experimental data measured during the heat-up and hydrogen discharging processes. The prediction based on the proposed model was found to be in good agreement with the experimental data in terms of the beds temperature evolution and the hydrogen discharging time. In addition, a parametric study is conducted on various MHBs with heat-fins or metal-foams that were designed to contain the same amount of ZrCo powder for comparison purposes. Our results clearly demonstrate that a superior MHB design should exhibit higher effective conductivity in the metal powder region and a lower overall thermal mass, which can be achieved by using metal-foam with optimum porosity. [ABSTRACT FROM AUTHOR]

In this investigation by experiments, it was proved that the thermal runaway can be used as a new high-performance method of desorption of hydrogen from metal-hydrides. On its kinetic and thermodynamic parameters, this method is considerably superior to requirements established by US Department of Energy for onboard hydrogen storage systems. For its processing, the thermal runaway does not require any certain temperature or pressure. It can work at any temperature and pressure of ambiance. The hydrogen desorption by the method of the thermal runaway runs with aid of electrochemical reactions. This is why this process is easily controllable by electrotechnical methods and hence it is far less inertial than the thermal processes used in the traditional thermo-chemical method of the hydrogen desorption from the metal-hydrides. [ABSTRACT FROM AUTHOR]

In the present work, hydrogen storage properties of Ti 0.32 Cr 0.43 V 0.25 alloy and its composite with TiMn 2 have been studied. The alloy and the composites have been evaluated for their structures, pressure composition isotherms, hydrogen storage capacity, kinetics of hydrogen absorption and hydrogen desorption temperatures. Ti 0.32 Cr 0.43 V 0.25 alloy shows maximum 3.33, 1.82 and 1.30 wt. % hydrogen storage capacities at 303, 348 and 423 K, respectively. (Ti 0.32 Cr 0.43 V 0.25 ) 0.95 (TiMn 2 ) 0.05 composite absorbs maximum 2.90, 1.80 and 1.40 wt. % of hydrogen at 303, 348 and 423 K, respectively. Kinetic study shows that the hydrogen absorption rate is faster for the composites at the initial chemical reaction stage, and later in hydrogen diffusion stage the hydrogen absorption rate decreases. The saturated composite hydrides show additional hydrogen desorption peak at lower temperature, which is important for practical application. [ABSTRACT FROM AUTHOR]

A three-dimensional hydrogen desorption model is developed and validated against the temperature evolution data measured on a cylindrical LaNi 5 metal hydride vessel. The equilibrium pressure for hydrogen desorption in LaNi 5 is derived as a function of the H/M atomic ratio and temperature based on the experimental data reported in the literature. In general, the numerical simulations are in good agreement with the experimental data, which confirms the validity and accuracy of the proposed desorption model. Both the calculated and measured temperature profiles exhibit an initial sharp drop, which is indicative of a relatively rapid hydrogen desorption rate compared to the heat supply rate from the vessel external walls at the early stages. On the other hand, the effect of heat supply becomes influential at the latter stages, leading to a smooth increase in vessel temperature. This numerical study suggests that the efficient design of a storage vessel and heating system is essential for achieving rapid hydrogen discharging performance. [ABSTRACT FROM AUTHOR]

Applying density functional theory, we investigate hydrogen absorption/desorption performances of synthesized Zr–η 2 –(C 2 H 2 ) and its ion. Comparing with light TM–C n H n systems, Zr–η 2 –(C 2 H 2 ) and its ion have a great advantage to trap hydrogen molecules at mild conditions. With reasonably good storage capacity (9.35 wt%) and ideal average binding energy (0.25 eV/H 2 ), Zr–η 2 –(C 2 H 2 ) is proposed as suitable hydrogen storage medium. Ionization of Zr–η 2 –(C 2 H 2 ) can effectively improve the H 2 adsorption energy. All the six molecular H 2 adsorbed on Zr–η 2 –(C 2 H 2 ) + are 100% released at 586.5 K under ambient pressure while the first adsorbed H 2 is remained strongly bound to Zr–η 2 –(C 2 H 2 ) even at 1619.3 K. [ABSTRACT FROM AUTHOR]

Magnesium hydride is a very promising material for solid-state hydrogen storage. However, some drawbacks have to be overcome to use it in real applications. The use of catalysts is a viable solution to lower the desorption temperature and increase the overall kinetics. An accurate model has been developed to study the mechanism of action of the catalyst and how it interacts with the interface MgH 2 –Mg, through which H atoms diffuse. The accurate evaluation of the work of adhesion and defect energy formation, versus the distance from the interface are linked to the atomic-scale structural distortion induced by the catalyst. Moreover, molecular dynamics simulations at several temperature provide a clear description of the desorption mechanism and an estimate of the desorption temperature. [ABSTRACT FROM AUTHOR]

The decomposition properties of Mg(BH 4 ) 2 ·2NH 3 combined with LiAlH 4 mixtures were investigated systematically. It revealed that the hydrogen desorption temperature shifted to 100 °C with the superior suppression of ammonia, and desorption rates were improved with the increased LiAlH 4 ratio (0.5, 1, 2), respectively. When the LiAlH 4 ratio was increased to 2, the binary system exhibited three dehydrogen steps with an onset temperature at 98 °C and 5.4 wt % H 2 desorbed rapidly at the same temperature, while no apparent evolution of H 2 was observed for individual Mg(BH 4 ) 2 ·2NH 3 and LiAlH 4 below 150 °C. The dehydrogenation rate of the system was improved by about 92% more than that of Mg(BH 4 ) 2 ·2NH 3 . These results indicate that the dehydrogenation of Mg(BH 4 ) 2 ·2NH 3 is enhanced significantly by the introduction of LiAlH 4 . The synergetic factor of the aided-cation effect and dihydrogen interaction may contribute to prevent the NH 3 group from being dissociated as ammonia. [ABSTRACT FROM AUTHOR]

The improvement of the capacity and rate of hydrogen absorption/desorption at the same time had been focus hydrogen storage field. A new method was proposed to prepare a new type sintered body with a special layer structure due to the crystal structure of the sintered body distinguish with a powder and alloy. Therefore, the sintered body not only effectively overcame the inconvenience from the powder on storage aspect, but also avoided negative factors of small surface area. The sintered body had a foam structure whose surface area was large, which provided a strong chemical channel for the physical absorption and chemical diffusion by generating hydrogen absorption phase Mg 2 Ni and catalytic phase NiTi, so that great improved the property of hydrogen absorption/desorption. The capacity of hydrogen absorption/desorption reach to 3% within 3 min and the highest capacity reach to 5.26% within 16 min; hydrogen desorption process was completed within 30 min and the released capacity was about 2%. [ABSTRACT FROM AUTHOR]

Mg 85 Ni 14 Ce 1 amorphous alloy films with different thicknesses, including 500 nm, 300 nm, 250 nm and 50 nm, are prepared by DC magnetron sputtering. The nanosize effect on the hydrogen desorption and cycling properties is studied. As the size decreases, hydrogen storage kinetics greatly increase. Moreover, the nanosized amorphous alloys reversibly absorb and desorb hydrogen with almost unchanged desorption kinetics at a low temperature of 120 °C. The structure of amorphous alloy can be fully recovered after hydrogen absorption and desorption cycles. It is shown that nanosized amorphous alloys are promising candidates for reversible hydrogen storage applications at moderate temperatures. [Display omitted] [ABSTRACT FROM AUTHOR]