The hydrogen absorption/desorption kinetic properties of MgH₂ can be effectively enhanced by doping specific catalysts. In this work, MOFs-derived NiCu@C nanoparticles (~15 nm) with regular core-shell structure were successfully prepared and introduced into MgH₂ (denoted as MgHNiCu@C). The onset and peak temperatures of hydrogen desorption of MgH₂–11 wt.% NiCu@C are 175.0 ℃ and 282.2 ℃, respectively. The apparent activation energy of dehydrogenated reaction is 77.2 ± 4.5 kJ/mol for MgH₂–11 wt.% NiCu@C, which is lower than half of that of the as-milled MgH₂. Moreover, MgH₂–11 wt.% NiCu@C displays great cyclic stability. The strengthening "hydrogen pumping" effect of reversible solid solutions Mg₂Ni(Cu)/Mg₂Ni(Cu)H₄ is proposed to explain the remarkable improvement in hydrogen absorption/desorption kinetic properties of MgH₂. This work offers a novel perspective for the design of bimetallic nanoparticles and beyond for application in hydrogen storage and other energy related fields.

Among the factors which restrict the large-scale utilization of magnesium-based hydride as a hydrogen storage medium, the high operating temperature, slow kinetics, and air stability in particular are key obstacles. In this work, a novel method, namely hydriding combustion synthesis plus short-term mechanical milling followed by air exposure, was proposed to synthesize air stable and autocatalytic magnesium nickel hydride (Mg₂NiH₄), which shows excellent hydrogen absorption/desorption kinetics, capacity retention and oxidation resistance. The short-term-milled Mg₂NiH₄ can desorb 2.97 wt.% hydrogen within 500 s at 230 °C. Even after exposure under air atmosphere for 67 days, it can still desorb 2.88 wt.% hydrogen within 500 s at 230 °C. The experimental and theoretical results both indicated that the surface of as-milled Mg₂NiH₄ was easy to be oxidized under air atmosphere. However, the in-situ formed Ni during air exposure of Mg₂NiH₄ improved the hydrogen desorption kinetics, and the formed surface passivation layer maintained the hydrogen storage capacity and avoided further poisoning, which we called autocatalytic and self-protective effect. Such a novel dual effect modified the reaction activity and oxidation resistance of the air-exposed Mg₂NiH₄. Our findings provide useful insights into the design and preparation of air stable metal-based hydride for large-scale utilization and long-term storage.