Development of AB₂-type TiZrCrMnFeCoV intermetallic high-entropy alloy for reversible room-temperature hydrogen storage

Intermetallic high-entropy alloys (HEAs) with C14 Laves phase structure have shown promise as hydrogen storage materials due to their ability to maintain the advantages of the AB₂-type hydrogen storage alloys while offering the potential for the improvement of hydrogen storage properties through the use of multi-principal elements. However, some intermetallic HEAs are limited in their ability to scale-up production using the low-cost induction melting method and reversible hydrogen storage at room temperature due to their extremely low equilibrium desorption pressure. In this work, intermetallic HEAs with reversible room-temperature hydrogen storage are designed using an empirical model based on calculation of the electronic and geometrical factors. An orthogonal experiment was conducted to optimize the composition and the optimal (Ti_1.3Zr_0.7)_1.1Cr_1.1Mn_1.8Fe_0.3Co_0.4V_0.4 HEA with a single C14 Laves phase was found to exhibit the best overall hydrogen performance. It can reversibly store 1.84 wt% hydrogen with a relatively low plateau hysteresis factor (0.71) and slope factor (0.89) at a temperature of 15 °C. The dehydrogenation enthalpy and entropy of the optimal HEA were determined to be 35.0 kJ mol⁻¹ and 115.3 J mol⁻¹ K⁻¹, respectively. To reduce the cost of HEAs, FeV80 was employed to replace the V. It was found that the optimal HEA could be successfully scaled-up for production, and our findings demonstrate the potential of intermetallic HEAs for efficient hydrogen storage.