Enhancing hydrogen storage properties of MgH2 using FeCoNiCrMn high entropy alloy catalysts

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.