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 degrees 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 H-2 at 225 degrees 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.