Studies of Ni-Mg catalyst for stable high efficiency hydrogen storage

•The Ni-Mg catalyst was rationally synthesized by wet chemical method.•Ni-Mg has a hydrogen storage capacity of 7.5 wt%, with rapid absorption/desorption kinetics.•MgNi phase formed during hydrogenation is conducive to subsequent dehydrogenation. Ni-Mg catalyst are applied for the hydrogen absorption/desorption. It exhibits a hydrogen storage capacity of 7.5 wt%, with rapid absorption/ desorption kinetic and stable reversible absorption/desorption cycling performance. Combining advanced characterization techniques and theoretical analysis shows that Ni facilitates hydrogenation process, and the new MgNi phase formed during the hydrogenation is conducive to subsequent dehydrogenation. This well explains the mechanism of the excellent H2 adsorption and desorption performance of the Ni-Mg catalyst. [Display omitted] Doping engineering is an effective strategy to improve the hydrogen storage capacity of magnesium-based materials. Here, we report a magnesium composite containing trace amounts of nickel catalyst (Ni-Mg), in which Ni and Mg layers form a new structural phase. The test shows that Ni-Mg composite has a hydrogen storage capacity of 7.5 wt%, with rapid absorption/desorption kinetics and stable reversible absorption/desorption performance on cycling. Ni-Mg exhibits a superior hydrogen storage performance as compared to the MgNi alloys and Mg-based materials previously reported in the literature. We conclude that a new MgNi phase and MgNi2 intermetallic compound are formed during the H2 adsorption process. Based on the theoretical calculations, we show that Ni facilitates hydrogenation by accelerating the dissociation of H2 molecules into the H atoms, while the MgNi phase formed during the hydrogenation is conducive to the subsequent dehydrogenation, promoting H atoms diffusion between the subsurface and the surface. This work provides a guidance for the development of the efficient hydrogen storage materials.