A Phase-Transition Catalyst Bidirectionally Enhances the Hydrogen Absorption/Desorption Kinetics of Mg/MgH₂

Magnesium-based H₂ storage material (MgH₂) exhibits exceptional prospects for application in the field of solid-state H₂ storage. However, its widespread utilization is hindered by slow H₂ absorption and desorption kinetics. To address this issue, this study proposes a catalytic strategy that leverages phase transitions in transition metal carbides to bidirectionally augment the kinetic properties of Mg/MgH₂, thereby improving its H₂ absorption and desorption capabilities. A phase transition catalyst, designated Mo₂C-N-CNTs, has been purposefully synthesized through a combination of ion exchange and high-temperature sintering. The Mg@Mo₂C-N-CNT composite shows a decrease in the hydrogenation activation energy (E_a) to 19.62 kJ/mol, with the corresponding dehydrogenation E_a value reduced to as low as 75.99 kJ/mol. A newly identified synergistic mechanism, facilitated by the “electronic conduit” effect, effectively catalyzes the dehydrogenation and hydrogenation of Mg/MgH₂ when Mo₂C phase transition catalysts are integrated with N-doped CNTs.