Effective catalytic effects of Mo2C MXene on the hydrogen storage in magnesium hydride

Abstract

Magnesium hydride (MgH₂) has received widespread attention because of its high hydrogen capacity and low cost, but the sluggish kinetics limited its practical application. Herein, the two-dimensional Mo₂C MXene was constructed to motivate the efficient hydrogen storage in MgH₂ for the first time. After doping 10 wt% Mo₂C MXene, the starting dehydriding temperature was lowered to 225 °C, presenting a 117 °C reduction compared with that of as-received MgH₂. The 10 wt% Mo₂C-containing MgH₂ sample could rapidly release 6.7 wt% H₂ in 13 min at 300 °C, and the product after hydrogen release could absorb 6.0 wt% H₂ in 12 min at 200 °C, showing superior hydriding and dehydriding kinetics. Moreover, the activation energy (E_a) of MgH₂–10 wt% Mo₂C (107.58 ± 1.57 kJ/mol) was obviously lower than that of pure MgH₂ (130.45 ± 1.97 kJ/mol), and the reduced activation energy explained the reduced dehydrogenation temperature and enhanced kinetics. Microstructure characterization revealed that Mo-species (Mo⁰ and Mo²⁺) formed during ball milling served as active species accelerated the hydriding/dehydriding reactions, and the uniformly distributed active species and the interaction between Mo and O jointly promoted the hydrogen storage properties of MgH₂.