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

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.