The effect of Sc addition on the hydrogen storage capacity of Ti0.32Cr0.43V0.25 alloy

• The ab initio calculation suggested Sc as the most suitable element in Ti–M–V alloys.
• Ti–Sc–V alloy shows the lowest hydrogen absorption energy among Ti–M–V alloys.
• The absorbed amount of hydrogen in Ti–Cr–V could be increased by addition of Sc.
• The capacity could be enhanced by heat treatment due to elimination of TiCr2.

The effect of the addition of 4th element on the hydrogen storage capacity of Ti0.32Cr0.43V0.25 alloy was evaluated by simulation and confirmed experimentally. The crystal lattice volume, phase formation energy, and hydrogen absorption energy of the alloys were calculated by ab initio calculation for the alloys containing the third-period transition metals as Sc, Cr, Mn, Fe, Co, Ni, Cu, and Zn. It was postulated that the hydrogen absorption would be favored by large crystal volume and low hydrogen absorption energy. The calculation suggested Sc as the most suitable element and the hydrogen capacities of a series of Ti0.32Cr0.43−xV0.25Scx alloys (x = 0.02–0.1) were determined accordingly. Among the alloys, the capacities of Ti0.32Cr0.41V0.25Sc0.02 and Ti0.32Cr0.39V0.25Sc0.04 alloys were higher than that of the Ti0.32Cr0.43V0.25 alloy. The capacity of both alloys could be enhanced further by the heat treatment at 1250 °C due to the elimination of the second-phase TiCr2.