Synergistic Effect of the Hydrogen Pump and Heterostructure Enables Superior Hydrogen Storage Performance of MgH₂

Abstract

Catalysis has been demonstrated to be effective in enhancing the kinetics of MgH 2 , which has been widely investigated as one of the most promising solid-state hydrogen storage materials. It is essential and challenging to design catalysts with high activity and to understand the corresponding interaction mechanisms between the catalysts and MgH 2 , especially for multiphase catalyst systems. In this study, an elaborated VS 2 / NiS 2 catalyst based on well-combined components and heterostructure is exploited to substantially improve the hydrogen storage performance of MgH 2 . Impressively, rapid dehydrogenation (3.4 wt % H 2 in 900 s at 498 K) and low-temperature hydrogenation (3.7 wt % H 2 in 7200 s at 348 K) properties are achieved in the MgH 2 −VS 2 /NiS 2 system. The activation energies for the hydrogen absorption/desorption are calculated to be 32.1/86.7 kJ mol −1 , which represents a considerable reduction of 60.9% and 43.6% compared to the as-milled MgH 2 , respectively. Detailed investigations reveal that the enhanced hydrogen absorption/desorption kinetics are mainly attributed to the synergistic effect induced by the in situ-formed Mg 2 Ni/VH 2 heterostructure and the "hydrogen pump" of Mg 2 Ni/Mg 2 NiH 4 . The Mg 2 Ni/VH 2 heterostructure elongate Mg−H bonds, while the "hydrogen pump" of Mg 2 Ni/Mg 2 NiH 4 facilitate H transfer. This work offers a fresh perspective for application of multicomponent catalysts in the field of metal hydrides.