In Situ Formation of Mg2Ni on Magnesium Surface via Hydrogen Activation for Improving Hydrogen Sorption Performance

Abstract

To improve the hydrogen sorption rate and lower the dehydrogenation temperature, the Mg2Ni was formed in situ on the Mg surface by the hydrogen activation from Mg–NiO and Mg–NiCl2 composites. Among these two, Mg–5NiO absorbs 6.19 wt % H2 in 40 min at 320 °C, considerably higher than Mg–5NiCl2 (5.52 wt % H2) or pure milled Mg (4.09 wt % H2). When compared with MgH2, the decomposition peak temperature and apparent activation energy of MgH2–5NiO are reduced by, respectively, 24.6 °C and 49.7 kJ/mol H2 while, respectively, 40.5 °C and 24 kJ/mol H2 for MgH2–5NiCl2. Micro-structural analysis indicates that the in situ formed Mg2Ni on the Mg surface is of critical importance for improving hydrogen storage performance of the material. The in situ formed Mg2Ni facilitates the dissociation of H2 molecules during the hydrogenation process and benefits the cleavage of the Mg–H bond during dehydrogenation for H2 formation. The strategy of in situ formation from precursors can inspire the design of solid material for hydrogen storage.