Stability Of Hydrides Research Articles

DFT investigations of doping effects on the structural stability, thermal diffusion, and absorption/desorption kinetics in cubic, hexagonal, and monoclinic Mg2NiHx hydrides

The pseudo-potential plane-wave method, based on Density Functional Theory (DFT) and using the Generalized Gradient Approximation (GGA), is applied to investigate the effects of progressive hydrogen insertion on the structural stability and energetics of Mg2NiHx hydrides. The obtained results indicate that Mg2Ni crystallizes in the hexagonal (P6222) structure. Taking into account the site preference of H atoms, the progressive hydrogenation of Mg2Ni favors the formation of Mg2NiHx hydrides in cubic (Fm-3m) and monoclinic (C2/c) phases rather than the parent hexagonal phase. The alloying effects of Cu, Y, Si, Ti, Cr, and Fe on the structural stability and absorption/desorption kinetics of monoclinic Mg2NiH4 are also investigated. More particularly, systems with Cu and Si additions have the lowest desorption temperatures, as confirmed by Molecular Dynamic (MD) calculations. The thermal diffusion is well observed in all studied compounds. The corresponding average thermal diffusion coefficients are mainly attributed to hydrogen atoms and are increased by the addition of Cu. These trends are expected to have an important role in phase transitions observed during hydrogen insertion. The present study based on DFT and MD calculations shows that doped Mg2NiHx are promising hydrides with interesting kinetic behavior. The obtained results can be useful for future experimental studies devoted to improving hydrogen absorption/desorption temperatures, low energy costs, and high atomic hydrogen storage capacities in Mg2Ni.

Generation of Surface Ga-H Hydride and Reactivity toward CO2.

Hydrogen adsorption on gallium oxide was investigated by in situ infrared (IR) spectroscopy over a temperature range of 30-450 °C. Both hydroxyl groups and Ga-H hydrides with a pair of characteristic bands at 3685 (3532) cm-1 and 2011 (1988) cm-1 were detected on the surface gallium oxide. The formation and stability of surface Ga-H hydrides were found to be highly dependent on the temperature of H2 dissociation. Through a combination of density functional theory (DFT) calculations and isotopic experiments, a mechanism involving both heterolytic and homolytic pathways for hydrogen dissociation was proposed for the generation of Ga-H hydrides. Furthermore, the reactivity of surface Ga-H hydrides was explored by their interactions with various probe molecules such as carbon dioxide, oxygen, and nitrogen. A potential reaction mechanism involving the attraction between nucleophilic hydrogen and positively charged intermediates was suggested during those hydrogenations.

The role of hydrogen in the synthesis of High-entropy alloys and their hydrides

The aim of this work is to present the new technique processes of formation of stable hydrides of High-entropy alloys (HEAs) with high hydrogen content. The essence of the proposed method is the sequential use of self-propagating high-temperature synthesis (SHS) method for producing the metal hydrides, followed by the formation of alloys in the hydride cycle (HC) method. Preliminary, the hydrides of three compositions of metal mixtures were synthesized in SHS: 0.2TiH2+0.2ZrH2+0.2HfH2+0.2VH2+0.2NbH2, 0.3TiH2+0.15ZrH2+0.15HfH2+0.2VH2+0.2NbH2 and 0.3TiH2+0.1ZrH2+0.1HfH2+0.2VH2+0.2NbH2+0.1MgH2. From the synthesized mixtures of metal hydrides, the HEAs were produced in HC. The resultant hard alloys Ti0.2Zr0.2Hf0.2V0.2Nb0.2, Ti0.3Zr0.15Hf0.15V0.2Nb0.2 and Ti0.3Zr0.15Hf0.15V0.2Nb0.2Mg0.1 without crushing combusted in Н2 at РH2 = 5–30 atm. in SHS mode. As a result, the hydrides of HEAs (Ti0.2Zr0.2Hf0.2V0.2Nb0.2)Н2.05, (Ti0.3Zr0.15Hf0.15V0.2Nb0.2)H2.05 and (Ti0.3Zr0.1Hf0.1V0.2Nb0.2 Mg0.1)H182 were synthesized with H2 content between 2.17 and 2.42 wt% and H/Me = 1.82–2.05. The repeating the hydrogenation-dehydrogenation processes for 1–3 times confirmed the exceptional cyclic stability of hydrides and the reversible high hydrogen storage capacity of the alloys. The regularities and the mechanism of formation of HEAs and their hydrides were elucidated. The applicability of combination of SHS and HC methods for synthesis of solid solutions of BCC structure HEAs and of their hydrogen-rich hydrides was demonstrated. The remarkable advantages of the developed efficient, low-energy consuming, waste-free and safe method for the synthesis of HEAs and their hydrides can be of commercial interest and attractive to industry, given the current needs for the development of renewable energy, in particular, the solid hydrogen storage facilities.

Designing multicomponent hydrides with potential high Tc superconductivity

While hydrogen-rich materials have been demonstrated to exhibit high Tc superconductivity at high pressures, there is an ongoing search for ternary, quaternary, and more chemically complex hydrides that achieve such high critical temperatures at much lower pressures. First-principles searches are impeded by the computational complexity of solving the Eliashberg equations for large, complex crystal structures. Here, we adopt a simplified approach using electronic indicators previously established to be correlated with superconductivity in hydrides. This is used to study complex hydride structures, which are predicted to exhibit promisingly high critical temperatures for superconductivity. In particular, we propose three classes of hydrides inspired by the Fm[Formula: see text]m RH[Formula: see text] structures that exhibit strong hydrogen network connectivity, as defined through the electron localization function. The first class [RH[Formula: see text]X[Formula: see text]Y] is based on a Pm[Formula: see text]m structure showing moderately high Tc, where the Tc estimate from electronic properties is compared with direct Eliashberg calculations and found to be surprisingly accurate. The second class of structures [(RH[Formula: see text])[Formula: see text]X[Formula: see text]YZ] improves on this with promisingly high density of states with dominant hydrogen character at the Fermi energy, typically enhancing Tc. The third class [(R[Formula: see text]H[Formula: see text])(R[Formula: see text]H[Formula: see text])X[Formula: see text]YZ] improves the strong hydrogen network connectivity by introducing anisotropy in the hydrogen network through a specific doping pattern. These design principles and associated model structures provide flexibility to optimize both Tc and the structural stability of complex hydrides.

Computational study of the mechanical stability, hydrogen storage and optoelectronic properties of new perovskite hydrides CsXH3 (X = Ca, Sr and Ba)

In this study, the physical properties of the perovskite hydrides CsXH3 (X = Ca, Sr and Ba) were explored using density functional theory (DFT) to assess their suitability for optoelectronic and hydrogen storage applications. The properties analyzed for these materials included hydrogen storage capacity, as well as structural, mechanical, electronic, and optical characteristics. These investigations were conducted using the GGA-PBE method within the ABINIT simulation code. Initially, the structural properties revealed that the lattice constants of the optimized unit cell structures of CsCaH3, CsSrH3 and CsBaH3 are 4.66, 4.80 and 5.25 Å, respectively. Additionally, the formation energy calculations proved that the selected materials are thermodynamically stable and can be synthesized. The mechanical stability of such hydrides has been confirmed by the results of the elastic constants that met the necessary stability criteria. Moreover, the hydrogen storage properties of the considered compounds revealed capacities of 1.71 wt%, 1.35 wt%, and 1.11 wt% for CsCaH3, CsSrH3 and CsBaH3, respectively, indicating their considerable potential as candidates for hydrogen storage applications. The electronic properties revealed that the three investigated materials exhibit semiconducting behavior with band gaps of 3.16, 2.84 and 2.18 eV for CsCaH3, CsSrH3 and CsBaH3, respectively. Additionally, various optical features including real ε1(ω) and imaginary ε2(ω) dielectric components, refractive index n(ω), absorption factor α(ω) were also investigated and implied that CsCaH3, CsSrH3 and CsBaH3 are suitable for optoelectronic devices. This study is the first to highlight the relevance of new materials CsCaH3, CsSrH3 and CsBaH3 for hydrogen storage and optoelectronic applications.

A precise prediction of structure stability and hydrogen storage capability of KCdH3 perovskite hydride using density functional theory calculations

Perovskite hydrides materials are acknowledged for hydrogen storage due to their high capacity, reversibility, thermodynamic stability, tunable nature, and potential low-cost solutions. In the current investigation, the four distinct cubic structures of perovskite hydride KCdH3 for the hydrogen storage are investigated with the help of density functional theory and providing valuable insights into stable phases. Electronic, thermal and entropy calculations are performed. Two out of four cubic structure are founded mechanically stable with the gravimetric storage capacity of be 5.5 cwt% and the volumetric storage capacity of 67.69 gH2l−1 which align with the standard situated by the U.S. Department of Energy for the year 2025. Notably, this study is the first comprehensive investigation of all four cubic phases of the KCdH3 compound. The promising hydrogen storage capabilities of these compounds shows the credibility for their effective use as a solid-state hydrogen storage material, and the research aims to further ascertain its stability and storage capacities.

Optimizing Hydride Stability in U-ZrHx Nuclear Fuel: The “Goldilocks Radius”

Nuclear-powered microreactors show great promise for opening new nuclear energy markets due to the flexibility offered by their rapid/streamlined in-factory fabrication, transportability, and self-regulating nature. The economic benefits of any commercialized nuclear reactor, however, rely on the system’s ability to produce large amounts of heat and efficiently convert that heat into electrical power reliably for long periods of time. Uranium-zirconium hydride (U-ZrHx) is currently being considered for compact reactor designs because it is a well-known nuclear fuel system that is self-moderating, but this fuel, which has historically been used for research reactors, has not been optimized for commercial power production. This paper analyzes the hydride stability of standard 304 stainless steel–clad U-ZrHx fuel under commercially relevant conditions. Fuel element design parameters, including physical dimensions, as-fabricated hydrogen content, burnup, peak fuel temperature, temperature gradient, operational fuel cycle duration, and volumetric heat generation rate, are discussed with a focus on hydrogen distribution and phase stability within the fuel element. Hydride stability declines more rapidly as the coolant temperature, burnup, and fuel cycle duration increase. Using a fuel-cladding gap material with heat transfer properties superior to air, such as helium or sodium, is essential to prolonging fuel hydride stability. The fuel’s physical dimensions are also important. At very small fuel diameters, the H/Zr ratio in the fuel meat decreases too rapidly due to the hydrogen content’s dependence on fuel meat volume. Conversely, the fuel meat temperature and temperature gradient exacerbate hydrogen loss at very large fuel diameters. We find that the most important parameter to consider when optimizing the hydride stability of U-ZrHx fuel is the relationship between the fuel meat radius and the power density in the fuel. A simple equation is empirically determined that relates the “Goldilocks radius,” that is, the fuel radius for which the H/Zr ratio is most stable, to the power density in the fuel.

Exploring hydrogen storage safety research by bibliometric analysis

The application of hydrogen energy is affected by the safety of hydrogen storage system. To grasp the current status of research and application in the research field of hydrogen storage safety and explore its research development trend, data analysis techniques, such as co-occurrence, co-citation, and burst detection, were adopted to conduct bibliometric analysis of the relevant literature. The study results show that the research hotspots of hydrogen storage safety mainly concentrate on six aspects: the stability of metal hydride hydrogen storage materials, the study of thermal management and stress relief in metal hydride reactors, the safety analysis of hydrogen fuel cells and hydrogen leakage monitoring, the analysis of leakage and explosion risks in hydrogen refueling stations, the study of filling pressure and temperature distribution in hydrogen storage tanks, and the study of safety issues in underground hydrogen storage. Mg-based hydride stability and underground hydrogen storage risk analyses are current research frontiers in hydrogen storage safety.

Catalytic mechanism of Nb2O5 and Ni on hydrogen storage properties of CeMg12-type alloy for automatic weather station emergency fuel cell

In this paper, CeMg12/Ni/Nb2O5 was prepared by mechanical ball milling technology for the sake of probing into the impact of Ni and Nb2O5 on microstructure and hydrogen sorption properties of alloys. The microstructure research results indicate that adding Nb2O5 can promote the formation of nanocrystal structure; through ball milling the Nb2O5 dispersed on the surface of alloy particles uniformly enhances the surface activity of the alloy and improves the hydrogen absorption and releasing kinetics of the alloy. The research on hydrogen absorption performance shows that the addition of Nb2O5 can significantly increase the hydrogen release platform pressure of the alloy hydride, the enthalpy value of hydrogen releasing process drops from 74.82 kJ/mol to 71.07 kJ/mol when the content of Nb2O5 is increased from 0 wt% to 9 wt%, the above qualitative and quantitative discussion further proves that Nb2O5 is beneficial for amending the thermodynamic stability of alloy hydride. Besides, adding Nb2O5 can remarkably reduce the hydrogen dissociation activation energy of experimental alloy hydride, ameliorating the dynamic performances of hydrogen release. The alloy with 9 wt% Nb2O5 has the smallest activation energy and the best performances of hydrogen release.

Constructing the combination bridge of aluminum hydride (AlH3) and polyvinylidene fluoride (PVDF) through the self-assembly of dopamine: Improving the stability and ignition properties of AlH3

Surface coating is an important method to solve the poor stability of aluminum hydride (AlH3). To overcome the difficulty of uneven coating of fluorine-containing polymers on the surface of AlH3, this study utilizes the adhesion properties of polydopamine (PDA) to establish a bridge between the oxide layer of AlH3 (Al2O3) and polyvinylidene fluoride (PVDF), so that Polyvinylidene fluoride (PVDF) was uniformly coated on the AlH3 surface, and a dual-core shell structure AlH3@PDA@PVDF composite was successfully prepared. Molecular dynamics simulations reveal significantly higher binding energy per unit area for γ-Al2O3@PDA/PVDF (1.2270 Kcal·mol−1·Å−2) compared to γ-Al2O3/PVDF (0.6644 Kcal·mol−1·Å−2), affirming that PDA can effectively enhance the interfacial interaction between AlH3 and PVDF. The morphology characterization and performance testing of raw AlH3 and AlH3@PDA@PVDF composite were carried out through SEM, XPS, FT-IR, DSC, VST, etc. The results indicate that through the interface modification of AlH3 by PDA, PVDF with a hydrophobic surface can be evenly coated on the surface of AlH3, causing the water contact angle (WCA) of the AlH3@PDA@PVDF composite to increase from 41° for the raw AlH3 to 124°. Furthermore, the total decomposition time of the AlH3@PDA@PVDF composite (2326 min) is improved by 1.8 times than that of the raw sample (1277 min), and its apparent activation energy (117.75 kJ·mol−1) was also higher than that of the raw sample (99.88 kJ·mol−1), indicating that coating with PDA and PVDF can improve the stability of AlH3. Ignition experiments demonstrate that the AlH3@PDA@PVDF composite has superior ignition reaction performance compared with the raw AlH3. Especially, adding a small amount of AlH3@PDA@PVDF composite can also significantly catalyze the thermal decomposition process of ammonium perchlorate (AP), reducing its high-temperature decomposition temperature from 405.37 °C to 352.20 °C.

First-principles investigation on the effect of Nb and Ta doping on the hydrogen storage performance of ZrCo

The ZrCo alloy has demonstrated significant potential in the storage of hydrogen and its isotopes, but there are still some issues such as insufficient dynamic properties. In this paper, the impact of Nb/Ta doping on the hydride stability of ZrCo was examined based on the density functional theory, and the improvement of H diffusion through Nb/Ta doping was investigated. The focal point lies in exploring the influence of Nb/Ta doping on the alloy’s resistance to poisoning and disproportionation. The results demonstrate that the crystal lattice maintains mechanical and thermodynamic stability even after Nb/Ta doping. Nb/Ta doping induces lattice contraction in ZrCo-Hx (x = 1.0–3.0) and reduce the enthalpy of formation, thereby facilitating cyclic hydrogen storage. Additionally, Nb/Ta doping enhances the diffusion performance of H atoms within O-containing lattice, improving the alloy’s resistance to poisoning. Furthermore, Nb/Ta doping lowers the energy barrier of H atoms escape from 8e sites, promoting anti-disproportionation.

Magnesium-Based Hydrogen Storage Alloys: Advances, Strategies, and Future Outlook for Clean Energy Applications.

Magnesium-based hydrogen storage alloys have attracted significant attention as promising materials for solid-state hydrogen storage due to their high hydrogen storage capacity, abundant reserves, low cost, and reversibility. However, the widespread application of these alloys is hindered by several challenges, including slow hydrogen absorption/desorption kinetics, high thermodynamic stability of magnesium hydride, and limited cycle life. This comprehensive review provides an in-depth overview of the recent advances in magnesium-based hydrogen storage alloys, covering their fundamental properties, synthesis methods, modification strategies, hydrogen storage performance, and potential applications. The review discusses the thermodynamic and kinetic properties of magnesium-based alloys, as well as the effects of alloying, nanostructuring, and surface modification on their hydrogen storage performance. The hydrogen absorption/desorption properties of different magnesium-based alloy systems are compared, and the influence of various modification strategies on these properties is examined. The review also explores the potential applications of magnesium-based hydrogen storage alloys, including mobile and stationary hydrogen storage, rechargeable batteries, and thermal energy storage. Finally, the current challenges and future research directions in this field are discussed, highlighting the need for fundamental understanding of hydrogen storage mechanisms, development of novel alloy compositions, optimization of modification strategies, integration of magnesium-based alloys into hydrogen storage systems, and collaboration between academia and industry.

Ball Milling Innovations Advance Mg-Based Hydrogen Storage Materials Towards Practical Applications.

Mg-based materials have been widely studied as potential hydrogen storage media due to their high theoretical hydrogen capacity, low cost, and abundant reserves. However, the sluggish hydrogen absorption/desorption kinetics and high thermodynamic stability of Mg-based hydrides have hindered their practical application. Ball milling has emerged as a versatile and effective technique to synthesize and modify nanostructured Mg-based hydrides with enhanced hydrogen storage properties. This review provides a comprehensive summary of the state-of-the-art progress in the ball milling of Mg-based hydrogen storage materials. The synthesis mechanisms, microstructural evolution, and hydrogen storage properties of nanocrystalline and amorphous Mg-based hydrides prepared via ball milling are systematically reviewed. The effects of various catalytic additives, including transition metals, metal oxides, carbon materials, and metal halides, on the kinetics and thermodynamics of Mg-based hydrides are discussed in detail. Furthermore, the strategies for synthesizing nanocomposite Mg-based hydrides via ball milling with other hydrides, MOFs, and carbon scaffolds are highlighted, with an emphasis on the importance of nanoconfinement and interfacial effects. Finally, the challenges and future perspectives of ball-milled Mg-based hydrides for practical on-board hydrogen storage applications are outlined. This review aims to provide valuable insights and guidance for the development of advanced Mg-based hydrogen storage materials with superior performance.

Large impact of phonon lineshapes on the superconductivity of solid hydrogen

Phonon anharmonicity plays a crucial role in determining the stability and vibrational properties of high-pressure hydrides. Furthermore, strong anharmonicity can render phonon quasiparticle picture obsolete questioning standard approaches for modeling superconductivity in these material systems. In this work, we show the effects of non-Lorentzian phonon lineshapes on the superconductivity of high-pressure solid hydrogen. We calculate the superconducting critical temperature TC ab initio considering the full phonon spectral function and show that it overall enhances the TC estimate. The anharmonicity-induced phonon softening exhibited in spectral functions increases the estimate of the critical temperature, while the broadening of phonon lines due to phonon-phonon interaction decreases it. Our calculations also reveal that superconductivity emerges in hydrogen in the Cmca − 12 molecular phase VI at pressures between 450 and 500 GPa and explain the disagreement between the previous theoretical results and experiments.

A novel carbon-induced-porosity mechanism for improved cycling stability of magnesium hydride

MgH2 has been extensively studied as one of the most ideal solid hydrogen storage materials. Nevertheless, rapid capacity decay and sluggish hydrogen storage kinetics hamper its practical application. Herein, a Ni/C nano-catalyst doped MgH2 (MgH2Ni/C) shows an improved hydrogen absorption kinetics with largely reduced activation energy. Particularly, the MgH2Ni/C displays remarkable cycling stability, which maintains a high capacity of 6.01 wt% (98.8 % of initial capacity) even after 50 full hydrogen ab/desorption cycles, while the undoped MgH2 counterpart retains only 85.2 % of its initial capacity. Detailed microstructure characterizations clearly reveal that particle sintering/growth accounts primarily for the deterioration of cycling performance of undoped MgH2. By comparison, MgH2Ni/C can maintain a stable particle size with a growing porous structure during long-term cycling, which effectively increases the specific surface of the particles. A novel carbon-induced-porosity stabilization mechanism is proposed, which can stabilize the proportion of rapid hydrogen absorption process, thus dominating the excellent cycling performance of MgH2Ni/C. This study provides new insights into the cycling stability mechanism of carbon-containing Mg-based hydrogen storage materials, thus promoting their practical applications.

Study on hydrogen storage properties of Ti–V–Fe–Mn alloys by modifying Ti/V ratio

The high stability of hydride phase has limited the improvement for the hydrogen storage properties of Ti–V based alloy at room temperatures. In this work, the stability of hydride was reduced by designing a low-price Ti–V–Fe–Mn alloy, and the effect of Ti/V ratio on the crystal structure and hydrogen storage properties was systematically investigated. The Ti40-xV40+xFe15Mn5 (x = 0, 2, 4, 6, 8) alloys were synthesized using arc melting, and the as-prepared alloys are all composed of single BCC phase. The lattice constant and cell volume decrease linearly with a lessening in Ti/V ratio. The reduction of cell volume makes it difficult for hydrogen atoms to diffuse, resulting in a sluggish hydrogen absorption rate. The dehydrogenation plateau in PCI curve rises and corresponding thermodynamics is optimized with a decrease in the lattice constant, and the hydrogen atoms are more readily to release, especially for Ti32V48Fe15Mn5 alloy with the dehydrogenation capacity of 1.83 wt% at 373 K. The result indicates the thermodynamic properties can be optimized by adjusting the lattice constant of Ti–V–Fe–Mn alloys, and hydrogen storage capacity is improved effectively. This study provides a reference for composition design of Ti–V–Fe–Mn alloys for high-density hydrogen storage.

Effective hydrogen storage in Na2(Be/Mg)H4 hydrides: Perspective from density functional theory

The utilization of hydrogen energy has garnered significant attention as a viable and environmentally friendly energy alternative. However, there exist some technological challenges pertaining to the storage of hydrogen. In this context, the present study utilizes first-principles calculations to examine the physical characteristics of Na2(Be/Mg)H4 hydrides to better understand their potential for use in hydrogen storage applications. The structure stability of Na2BeH4 and Na2MgH4 hydrides is assessed by formation enthalpy and phonon dispersion calculations. Elastic constants have been utilized to determine the elastic and mechanical stabilities of the studied hydrides. Both hydrides satisfy the established Born stability criteria, suggesting that both Na2BeH4 and Na2MgH4 are mechanically stable compounds. The assessment of electronic properties reveals that Na2BeH4 and Na2MgH4 have semiconducting characteristics with direct and indirect band gaps of 2.22 and 3.10 eV, respectively. Furthermore, various optical characteristics have been evaluated and compared. The computed values of gravimetric and volumetric hydrogen storage capacities for Na2BeH4 (Na2MgH4) hydrides are 6.78 (5.38) wt% and 85.11 (62.78) gH2l−1, respectively, fulfilling the standard set by US-DOE for 2025. This study suggests that both Na2BeH4 and Na2MgH4 hydrides have the potential to be an incredibly efficient choice for solid-state hydrogen storage.

A Computational Investigation of Lithium‐Based Metal Hydrides for Advanced Solid‐State Hydrogen Storage

AbstractHydrogen storage is a crucial step in commercializing hydrogen‐based energy production. Solid‐state hydrogen storage has gained much attention from researchers and needs extensive research. In the present study, we investigate the structural, mechanical, and optoelectronic properties of lithium‐based LiAH3 (A=Mn, Fe, Co) metal hydrides to elucidate their potential for solid‐state hydrogen storage. First, we evaluate the structure stability of LiAH3 hydrides using formation enthalpies calculations. Then, the mechanical stability is determined by elastic stiffness constants, which reveal that LiAH3 hydrides are stable mechanically as they meet the Born stability requirements. Electronic band structure calculations manifest that all LiAH3 hydrides possess a metallic character. Several optical properties have been discussed in detail. The gravimetric hydrogen storage capacities of LiMnH3, LiFeH3 and LiCoH3 hydrides are 4.65, 4.60 and 4.39 wt%, respectively, achieving the target of US‐DOE for rechargeable equipment. Additionally, we have determined the volumetric hydrogen storage capacities (Cv) for all LiAH3 hydrides. It is worth mentioning that the highest Cv values have been obtained to be 180.80, 188.18 and 177.25gH2l−1 for LiMnH3, LiFeH3 and LiCoH3 hydrides, respectively, which have achieved the US‐DOE target set for 2025. Our investigation predicts the applicability of lithium‐based hydrides as promising solid‐state hydrogen storage materials.

EFFECT OF Sc ON THE HYDROGEN-STORAGE PERFORMANCE OF Mg2Ni: A FIRST-PRINCIPLES STUDY

The effect of metal scandium (Sc) on the hydrogen-storage properties of the magnesium-nickel (Mg2Ni) alloy has been explored using the ultrasoft pseudopotential approach, rooted in the principles of Density Functional Theory (DFT). The binding energy, lattice constant, enthalpy of formation, standard enthalpy of reaction, charge density, density of states and bond order for the Mg2-xScxNi (x = 0, 0.25, 0.5, 1) alloys and their hydrides were calculated. Furthermore, the analysis of the atomic bonding and the structural stability of Mg2-xScxNi and hydrides were also facilitated. The results show that the preference site of the Sc atom in Mg2-xScxNi (x = 0, 0.25, 0.5, 1) alloys is Mg (6i) under the condition of a Sc doping concentration of 0.25. This causes a decrease in the stability of the Mg1.75Sc0.25Ni alloy. Moreover, the addition of Sc to Mg2-xScxNiH4 weakens the interaction of H-Ni and H-Mg, thereby facilitating the hydrogen-release reaction and effectively enhancing the hydrogen-release capability of Mg2-xScxNiH4.

Study on Microstructure and Hydrogen Storage Properties of Mg80Ni16−xAlxY4 (x = 2, 4, 8) Alloys

Mg80Ni16−xAlxY4 (x = 2, 4, 8) alloys were prepared by induction levitation melting, and the effect of substitution of Al for Ni on the microstructure and hydrogen storage properties was studied in the present work. The results illustrated that the solidification path, phase constitution, and grain size were significantly altered by Al addition. Appropriate Al addition improved abundance and grain refinement of the Mg, Mg2Ni, and Mg15NiY ternary eutectic. But as Al further increased, Mg solidified independently rather than in the formation of the ternary eutectic. More Al favored the formation of Al3Ni2Y but suppressed Mg2Ni and YMgNi4. Although the hydrogen absorption activation and the kinetic property deteriorated, the thermodynamic stability of hydrides was enhanced by adding Al. Hydrogen absorption ability under low pressure was improved, and the Mg80Ni8Al8Y4 alloy could absorb nearly 3.5 wt% hydrogen under 1 bar hydrogen at 250 °C.