Theoretical prediction of structure, electronic and optical properties of VH2 hydrogen storage material

The vanadium hydrides have better hydrogen storage capacity in comparison to the other metal hydrides. Although the structure of VH2 hydride has been reported, the structural stability, electronic and optical properties of VH2 hydride are unclear. To solve these problems, we apply the first-principles method to study the structural stability, electronic and optical properties of VH2 hydrides. Similar to the metal dihydrides, four possible VH2 hydrides such as the cubic (Fm-3m), tetragonal (I4/mmm), tetragonal (P4(2)/mnm) and ortho-rhombic (Pnma) are designed. The result shows that the cubic VH2 hydride is a thermo-dynamic and dynamical stability. In particular, the tetragonal (I4/mmm) and the orthorhombic (Pnma) VH2 hydrides are firstly predicted. It is found that these VH2 hydrides show metallic behavior. The electronic interaction of V (D-state)-H (s-state) is beneficial to improve the hydrogen storage in VH2 hydride. In addition, the formation of V-H bond can improve the structural stability of VH2 hydride. Based on the analysis of optical properties, it is found that all VH2 hydrides show the ultraviolet response. Compared to the tetragonal and orthorhombic VH2 hydrides, the cubic VH(2 )hydride has better storage optical proper-ties. Therefore, we believe that the VH2 hydride is a promising hydrogen storage material. (C) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Vanadium hydrides have better hydrogen storage capacity, with cubic VH2 hydride showing stability and tetragonal and orthorhombic VH2 hydrides exhibiting metallic behavior beneficial for hydrogen storage.