Optimizing FeCoNiCrTi high-entropy alloy with hydrogen pumping effect to boost de/hydrogenation performance of magnesium hydride

The exploration of efficient, long-lived and cost-effective transition metal catalysts is highly desirable for the practical hydrogen storage of magnesium hydride (MgH₂) in sustainable energy devices. Herein, FeCoNiCrTi high-entropy alloy (HEA) nanosheets were prepared via a facile wet chemical ball milling strategy and they were introduced into MgH₂ to boost the hydrogen storage performance. The refined HEA exhibited superior catalytic activity on MgH₂. In contrast to additive-free MgH₂, the initial desorption temperature of the constructed MgH₂-HEA composite was reduced from 330.0 to 198.5 °C and a remarkable 51% reduction in the dehydrogenation activation energy was achieved. Besides, the MgH₂-HEA composite only required one-twentieth time of that consumed by pure MgH₂ to absorb 5.0 wt% of H₂ at 225 °C. The synergy between the “hydrogen pumping” effect of Mg₂Ni/Mg₂NiH₄ and Mg₂Co/Mg₂CoH₅ couples, as well as the good dispersion of Fe, Cr and Ti on the surface of MgH₂ contributed to the enhanced de/hydrogenation performance of the MgH₂-HEA composites. This study furnishes important steering for the design and fabrication of multiple transition metal catalysts and may push the commercial application of magnesium-based hydrides one step forward.