First-principle investigation of hydrogen solubility and diffusivity in transition metal-doped vanadium membranes and their mechanical properties

Vanadium-based materials are considered ideal for hydrogen separation membranes owing to their higher hydrogen permeability and mechanical strength and lower cost compared with other widely used materials such as Pd alloys. However, pure V exhibits severe hydrogen embrittlement, which is often solved by alloying. In the present study, we used first-principles method to systematically calculate the hydrogen solubility, diffusivity, and other mechanical properties of different V-based binary alloys, namely, V-Co, V-Mo, V-Pd, V-Ru, and V-W. The alloys were found to possess stable crystal structures, and on exposure to hydrogen, the H atoms preferentially occupied the tetrahedral interstitial sites (TISs) in both the pure V and alloy within the material matrix, preferentially diffusing between TISs. The hydrogen diffusion coefficients of the different alloys decreased in the order V-Pd > V-Co > V-Ru > V -Mo > V-W. The alloys and their hydrides also exhibited good mechanical properties, with their resistances to hydrogen embrittlement decreasing in the order V-Co > V-Ru > V-Pd > V-Mo > V-W. This revealed that the resistance to hydrogen embrittlement of the alloy increased with decreasing atomic size of the alloying element. The findings of this study promise to facilitate the development of novel V-alloy membranes for hydrogen separation and purification. (C) 2019 Elsevier B.V. All rights reserved.