Pushing the Boundaries of solid-state hydrogen storage: A Refined study on TiVNbCrMo high-entropy alloys

This study investigates the development of Ti₂₅V₃₀Nb₁₀Cr_35−xMo_x (x = 2, 4, and 6) high-entropy alloys (HEAs) for enhanced hydrogen storage performance. Alloys with tailored atomic radii and uniform valence electron concentration (VEC) were designed to obtain homogeneous single-phase body-centered cubic (BCC) solid solutions in combination with the CALPHAD method. Pressure-Composition-Temperature (PCT) curves for the Ti₂₅V₃₀Nb₁₀Cr₃₁Mo₄ alloy at 323 K revealed a remarkable reversible hydrogen storage capacity of 2.24 wt%, marking an unprecedented milestone within BCC high-entropy hydrogen storage alloys. The investigation reveals an unexpected reduction in maximum hydrogen storage with increased Mo content, challenging conventional expectations. The findings in this study offer insights into the intricate balance between chemical interactions and atomic structure, proposing the bulk modulus as a novel parameter for evaluating hydrogen release performance in HEAs. This work lays a foundation for future research in optimizing HEAs for efficient and reversible solid-state hydrogen storage.