Ni_0.6Zn_0.4O Synthesised via a Solid-State Method for Promoting Hydrogen Sorption from MgH₂

Magnesium hydrides (MgH₂) have drawn a lot of interest as a promising hydrogen storage material option due to their good reversibility and high hydrogen storage capacity (7.60 wt.%). However, the high hydrogen desorption temperature (more than 400 °C) and slow sorption kinetics of MgH₂ are the main obstacles to its practical use. In this research, nickel zinc oxide (Ni_0.6Zn_0.4O) was synthesized via the solid-state method and doped into MgH₂ to overcome the drawbacks of MgH₂. The onset desorption temperature of the MgH₂-10 wt.% Ni_0.6Zn_0.4O sample was reduced to 285 °C, 133 °C, and 56 °C lower than that of pure MgH₂ and milled MgH₂, respectively. Furthermore, at 250 °C, the MgH₂-10 wt.% Ni_0.6Zn_0.4O sample could absorb 6.50 wt.% of H₂ and desorbed 2.20 wt.% of H₂ at 300 °C within 1 h. With the addition of 10 wt.% of Ni_0.6Zn_0.4O, the activation energy of MgH₂ dropped from 133 kJ/mol to 97 kJ/mol. The morphology of the samples also demonstrated that the particle size is smaller compared with undoped samples. It is believed that in situ forms of NiO, ZnO, and MgO had good catalytic effects on MgH₂, significantly reducing the activation energy and onset desorption temperature while improving the sorption kinetics of MgH₂.