Development of Ti–V–Cr–Mn–Mo–Ce high‐entropy alloys for high‐density hydrogen storage in water bath environments

Abstract The V‐based body‐centered cubic (BCC)‐type hydrogen storage alloys have attracted significant attention due to their high theoretical hydrogen storage capacity of 3.80 wt%. However, their practical application faces challenges related to low dehydriding capacity and poor activation performance. To overcome these challenges, a BCC‐type Ti–V–Cr–Mn–Mo–Ce high‐entropy alloy (HEA) with an effectively dehydriding capacity of 2.5 wt% above 0.1 MPa was prepared. By introduction of Mo and conducting heat treatment, the precipitation of Ti‐rich phase in HEA was successfully suppressed, resulting in improved compositional uniformity and dehydriding capacity. Consequently, the effective dehydriding capacity increased significantly from 0.60 wt% to 2.50 wt% at 65 °C, surpassing that of other types of hydrogen storage alloys under the same conditions. Moreover, the addition of 1 wt% Ce enabled initial hydrogen absorption at 25 °C without the need for activation at 400 °C. Furthermore, Ce doping reduced the dehydriding activation energy of the Ti–V–Cr–Mn–Mo–Ce HEA from 52.71 to 42.82 kJ·mol −1 . Additionally, the enthalpy value of dehydrogenation decreased from 46.89 to 17.96 kJ·mol −1 , attributed to a decrease in the hysteresis factor from 0.68 to 0.52. These findings provide valuable insights for optimizing the hydrogen storage property of HEA.