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

Catalysis has been demonstrated to be effective in enhancing the kinetics of MgH2, 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 MgH2, especially for multiphase catalyst systems. In this study, an elaborated VS2/NiS2 catalyst based on well-combined components and heterostructure is exploited to substantially improve the hydrogen storage performance of MgH2. Impressively, rapid dehydrogenation (3.4 wt % H2 in 900 s at 498 K) and low-temperature hydrogenation (3.7 wt % H2 in 7200 s at 348 K) properties are achieved in the MgH2–VS2/NiS2 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 MgH2, respectively. Detailed investigations reveal that the enhanced hydrogen absorption/desorption kinetics are mainly attributed to the synergistic effect induced by the in situ-formed Mg2Ni/VH2 heterostructure and the "hydrogen pump" of Mg2Ni/Mg2NiH4. The Mg2Ni/VH2 heterostructure elongate Mg–H bonds, while the "hydrogen pump" of Mg2Ni/Mg2NiH4 facilitate H transfer. This work offers a fresh perspective for application of multicomponent catalysts in the field of metal hydrides.