Hydrogen Desorption Kinetics of V₃₀Nb₁₀(Ti_xCr_1–x)₆₀ High-Entropy Alloys

In recent years, high-entropy alloys (HEAs) have attracted wide attention for their enormous hydrogen storage potential, fast hydrogen absorption kinetics, and a wide range of composition selectivity, and the fact that alloys with body-centered cubic (BCC) structure are considered to possess large capacity. Herein, three V₃₀Nb₁₀(Ti_xCr_1–x)₆₀ HEAs with different Ti contents (Ti25, Ti30, Ti35) forming BCC structures were designed using the method of CALPHAD. The microstructure characteristics and the hydrogen storage performances, especially the kinetics of hydrogen desorption, were systematically investigated. The results show that after absorbing ~3.7 wt.% hydrogen at 300 K with 100 bar hydrogen pressure, the studied alloys exhibit similar hydrogen release behaviors at different temperatures. Taking the V₃₀Nb₁₀Ti₂₅Cr₃₅ alloy as an example, it was able to release 1.96 wt.%, 2.21 wt.%, and 2.48 wt.% of hydrogen at 353, 373, and 423 K, respectively. The higher the temperature, the faster the hydrogen desorption kinetics and the more hydrogen released. The hydrogen desorption kinetics of the alloys were successfully fitted with the Ginstling–Brounshtein model, and the main rate-controlling step was diffusion. In addition, the diffusion activation energy of hydrogen desorption decreases with the substitution of Cr content. The present study is expected to provide valuable information for the better development of high-entropy-based hydrogen storage alloys.