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Refractory high-entropy alloys (HEAs) show promise for novel hydrogen storage technology, but addressing their limited gravimetric hydrogen storage capacity necessitates exploration of light alloying elements including Mg and Al. Here, we employ density-functional theory to investigate the hydrogen desorption energetics of Ti0.325V0.275Zr0.125Nb0.275 alloy and the impact of doping with Mg and Al. Our analysis reveals that Mg and Al addition thermodynamically destabilize the Ti0.325V0.275Zr0.125Nb0.275-hydride and lower its storage capacity. The observed destabilization is attributed to reduced chemical contributions to the desorption enthalpy in the Mg and Al-doped hydrides. Detailed examination of the electronic density of states, electron localization function, and crystal orbital Hamilton population analysis unveils fundamental features of chemical bonding in these hydrides. Notably, H-H antibonding states occur for hydrogen atoms located in the nearest-neighbor interstices of Mg and Al atoms. Charge transfer facilitates formation of these antibonding states. This comprehensive analysis enhances our understanding of the intricate interplay between electronic structure, hydrogen desorption energetics, and chemical bonding in HEA hydrides, offering valuable insights for the design and optimization of advanced hydrogen storage materials.

Refractory high-entropy alloys (HEAs) show promise for novel hydrogen storage technology, but addressing their limited gravimetric hydrogen storage capacity necessitates exploration of light alloying elements including Mg and Al. Here, we employ density-functional theory to investigate the hydrogen desorption energetics of Ti0.325V0.275Zr0.125Nb0.275 alloy and the impact of doping with Mg and Al. Our analysis reveals that Mg and Al addition thermodynamically destabilize the Ti0.325V0.275Zr0.125Nb0.275-hydride and lower its storage capacity. The observed destabilization is attributed to reduced chemical contributions to the desorption enthalpy in the Mg and Al-doped hydrides. Detailed examination of the electronic density of states, electron localization function, and crystal orbital Hamilton population analysis unveils fundamental features of chemical bonding in these hydrides. Notably, H-H antibonding states occur for hydrogen atoms located in the nearest-neighbor interstices of Mg and Al atoms. Charge transfer facilitates formation of these antibonding states. This comprehensive analysis enhances our understanding of the intricate interplay between electronic structure, hydrogen desorption energetics, and chemical bonding in HEA hydrides, offering valuable insights for the design and optimization of advanced hydrogen storage materials.

Refractory high-entropy alloys (HEAs) show promise for novel hydrogen storage technology, but addressing their limited gravimetric hydrogen storage capacity necessitates exploration of light alloying elements including Mg and Al. Here, we employ density-functional theory to investigate the hydrogen desorption energetics of Ti0.325V0.275Zr0.125Nb0.275 alloy and the impact of doping with Mg and Al. Our analysis reveals that Mg and Al addition thermodynamically destabilize the Ti0.325V0.275Zr0.125Nb0.275-hydride and lower its storage capacity. The observed destabilization is attributed to reduced chemical contributions to the desorption enthalpy in the Mg and Al-doped hydrides. Detailed examination of the electronic density of states, electron localization function, and crystal orbital Hamilton population analysis unveils fundamental features of chemical bonding in these hydrides. Notably, H-H antibonding states occur for hydrogen atoms located in the nearest-neighbor interstices of Mg and Al atoms. Charge transfer facilitates formation of these antibonding states. This comprehensive analysis enhances our understanding of the intricate interplay between electronic structure, hydrogen desorption energetics, and chemical bonding in HEA hydrides, offering valuable insights for the design and optimization of advanced hydrogen storage materials., QC 20240813

Refractory high-entropy alloys (HEAs) show promise for novel hydrogen storage technology, but addressing their limited gravimetric hydrogen storage capacity necessitates exploration of light alloying elements including Mg and Al. Here, we employ density-functional theory to investigate the hydrogen desorption energetics of Ti0.325V0.275Zr0.125Nb0.275 alloy and the impact of doping with Mg and Al. Our analysis reveals that Mg and Al addition thermodynamically destabilize the Ti0.325V0.275Zr0.125Nb0.275-hydride and lower its storage capacity. The observed destabilization is attributed to reduced chemical contributions to the desorption enthalpy in the Mg and Al-doped hydrides. Detailed examination of the electronic density of states, electron localization function, and crystal orbital Hamilton population analysis unveils fundamental features of chemical bonding in these hydrides. Notably, H-H antibonding states occur for hydrogen atoms located in the nearest-neighbor interstices of Mg and Al atoms. Charge transfer facilitates formation of these antibonding states. This comprehensive analysis enhances our understanding of the intricate interplay between electronic structure, hydrogen desorption energetics, and chemical bonding in HEA hydrides, offering valuable insights for the design and optimization of advanced hydrogen storage materials.

Refractory high-entropy alloys (HEAs) show promise for novel hydrogen storage technology, but addressing their limited gravimetric hydrogen storage capacity necessitates exploration of light alloying elements including Mg and Al. Here, we employ density-functional theory to investigate the hydrogen desorption energetics of Ti0.325V0.275Zr0.125Nb0.275 alloy and the impact of doping with Mg and Al. Our analysis reveals that Mg and Al addition thermodynamically destabilize the Ti0.325V0.275Zr0.125Nb0.275-hydride and lower its storage capacity. The observed destabilization is attributed to reduced chemical contributions to the desorption enthalpy in the Mg and Al-doped hydrides. Detailed examination of the electronic density of states, electron localization function, and crystal orbital Hamilton population analysis unveils fundamental features of chemical bonding in these hydrides. Notably, H-H antibonding states occur for hydrogen atoms located in the nearest-neighbor interstices of Mg and Al atoms. Charge transfer facilitates formation of these antibonding states. This comprehensive analysis enhances our understanding of the intricate interplay between electronic structure, hydrogen desorption energetics, and chemical bonding in HEA hydrides, offering valuable insights for the design and optimization of advanced hydrogen storage materials.

Refractory high-entropy alloys (HEAs) show promise for novel hydrogen storage technology, but addressing their limited gravimetric hydrogen storage capacity necessitates exploration of light alloying elements including Mg and Al. Here, we employ density-functional theory to investigate the hydrogen desorption energetics of Ti0.325V0.275Zr0.125Nb0.275 alloy and the impact of doping with Mg and Al. Our analysis reveals that Mg and Al addition thermodynamically destabilize the Ti0.325V0.275Zr0.125Nb0.275-hydride and lower its storage capacity. The observed destabilization is attributed to reduced chemical contributions to the desorption enthalpy in the Mg and Al-doped hydrides. Detailed examination of the electronic density of states, electron localization function, and crystal orbital Hamilton population analysis unveils fundamental features of chemical bonding in these hydrides. Notably, H-H antibonding states occur for hydrogen atoms located in the nearest-neighbor interstices of Mg and Al atoms. Charge transfer facilitates formation of these antibonding states. This comprehensive analysis enhances our understanding of the intricate interplay between electronic structure, hydrogen desorption energetics, and chemical bonding in HEA hydrides, offering valuable insights for the design and optimization of advanced hydrogen storage materials.

Doping can modify the properties of metal hydrogen storage materials significantly. Currently, the metal doping is a frequent strategy, while the non-metal cation doping has not been examined extensively so far. In this study, the effects of NH4+ doping on the hydrogen storage properties of different metal hydrides, including TiH2, Ti0·25V0·25Nb0·25Zr0·25H2, Ti0·5V0·5H2 and VH2, are investigated by first-principles calculations. It is found that the NH4+ presents a good affinity for metal hydrides and the NH4+ incorporation leads to charge redistribution and formation of dihydrogen bond. Furthermore, the NH4+ doping in metal hydrides is favorable for enhancing the hydrogen storage capacity and decreasing the thermal stability simultaneously. The possible reason for the NH4+ doping induced destabilization in metal hydrides is the relatively weak interaction between NH4+ and hydrogen atoms., QC 20230707

Metal hydrogen storage materials have been the focus of intensive research in the field of hydrogen-based economy. An outstanding question is that the number of hydrogen atoms accommodated in metal hydrides is generally much below the number of interstices, which limits their hydrogen storage capacities. Unlike traditional FCC metal hydrides where hydrogen can only occupy tetrahedral interstices, this study demonstrates that hydrogen can also occupy octahedral interstices in FCC high entropy alloy (HEA) hydrides, which leads to the violation of the Switendick criterion. For Ti25V25Nb25Ta25 and Ti25V25Nb25Zr25 HEAs, nearly 20% and 17.5% of octahedral interstices can be occupied by hydrogen, respectively. The anomalous hydrogen occupation mainly originates from the intrinsic electron delocalization between hydrogen atoms in HEA hydrides, which presents a sharp contrast to traditional metal hydrides. Such electron delocalization decreases repulsive interactions between hydrogens and promotes the electron localization at octahedral interstices. Additionally, this study reveals that hydrogen occupation at octahedral interstices enhances the structural disordering and decreases the thermal stability of HEA hydrides, which will be beneficial to reduce the dehydrogenation temperature. The presented results may provide a new strategy for the design of high-density storage materials., QC 20220411