Synergistic catalytic effect of carbon-coated Ni/MnO bimetallic nanospheres on the hydrogen storage performance of magnesium hydride

Magnesium hydride (MgH 2 ) is regarded as a promising solid-state hydrogen storage material with high capacity and abundant resources, while its large-scale application is limited because of the inherent thermodynamic and kinetic issues. In this study, a nitrogen-doped carbon-coated Ni/MnO nanosphere catalyst (Ni/MnO@NC) was synthesized to enhance the hydrogen storage performance of MgH 2 by lowering the operating temperature and improving kinetic properties. Incorporation of 10 wt% Ni/MnO@NC lowered the onset dehydrogenation temperature of MgH 2 to 225.2 ℃ and reduced the dehydrogenation activation energy to 97.68 kJ/mol. At temperatures as low as 50 ℃, MgH 2 -Ni/MnO@NC composite achieved 2.92 wt% hydrogen absorption within 30 min. Moreover, the composite retains 97.4 % of its initial capacity after 30 cycles. Mechanistic analysis indicates that the superior hydrogen storage performance arises from synergistic catalysis among intermediate and derived phases, including the hydrogen pump effect of Mg 2 Ni/Mg 2 NiH 4 , enhancement of electron transfer by multivalent Mn, and suppression of MgH 2 particle aggregation and growth by nitrogen-doped carbon. These findings put forward a promising strategy to advance the practical application of MgH 2 in hydrogen storage systems.