Abstract: Herein, we report the successful preparation of the FeCoNiCrMn high entropy alloy (HEA) loaded MgH₂ and HEA's effect on the hydrogen storage properties of Mg/MgH₂. The HEA shows high catalytic activity toward hydrogen dissociation and recombination reaction, and successfully suppressed activation energy of dehydrogenation reaction from 151.9 to 90.2 kJ mol^-1. Moreover, part of Co and Ni can react with Mg, and produce Mg₂Co/Mg₂CoH₅ and Mg₂Ni/Mg₂NiH₄ during the hydrogen storage processes, further enhancing dehydrogenation reaction through the “hydrogen pumping” mechanism. As a result, the MgH₂-5 wt% HEA composite can release 5.6 wt% of H₂ at 280 °C within 10 min, and absorb 5.5 wt% H₂ within 0.5 min at 150 °C. The loaded HEA shows robustness against particle aggregation, leading to stable reversible hydrogen storage processes at least 50 times. These findings show the synergistic effects of HEA on Mg-based hydrogen storage materials, providing an additional degree of freedom for catalyst design.

Key words: Hydrogen storage, Magnesium hydride, High entropy alloy, Catalytic effects