Development of Fe-containing BCC hydrogen storage alloys with high vanadium concentration

Vanadium-based alloys are promising hydrogen storage materials which reversibly absorb hydrogen > 2.0 wt% under ambient conditions. In present study, we systematically investigated the V-Ti-Cr-Fe quaternary alloys with V concentration of 65–80 at% and discussed the relationship between hydrogen sorption properties and lattice parameter (a) and valence electron density (e/a). When 3.023 ≤ a ≤ 3.031 Å and e/a ≤ 5.12, the alloys show the hydrogen desorption amount ≥ 2.30 wt% and desorption plateau pressure ≥ 0.1 MPa at 298 K. More interestingly, compared to the Fe-free V75-Ti-Cr (Ti/Cr = 0.9) alloy, addition of 1–3 at% Fe could improve the hydrogen desorption amount and plateau pressure. The optimized alloy, V75-Ti-Cr-Fe2 (Ti/Cr = 0.9), shows a reversible hydrogen capacity of 2.46 wt% at 298 K in the 1st cycle and the capacity retention rate of 96 % after 100 cycles.