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 ℃, presenting a 117 ℃ 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 ℃, and the product after hydrogen release could absorb 6.0 wt% H₂ in 12 min at 200 ℃, 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.

Designing catalysts with high catalytic activity and stability is the key to achieve the commercial application of MgH₂. Herein, the sulfur doped Ti₃C₂ (S-Ti₃C₂) was successfully prepared by heat treatment of Ti₃C₂ MXene under Ar/H₂S atmosphere to facilitate the hydrogen release and uptake from MgH₂. The S-Ti₃C₂ exhibited pleasant catalytic effect on the hydriding/dehydriding kinetics and cyclic stability of MgH₂. The addition of 5 wt% S-Ti₃C₂ into MgH₂ resulted in a reduction of 114 ℃ in the starting dehydriding temperature compared to pure MgH₂. MgH₂ + 5 wt% S-Ti₃C₂ sample could quickly release 6.6 wt% hydrogen in 17 min at 220 ℃, and 6.8 wt% H₂ was absorbed in 25 min at 200 ℃. Cyclic testing revealed that MgH₂ + 5 wt% S-Ti₃C₂ system achieved a reversible hydrogen capacity of 6.5 wt%. Characterization analysis demonstrated that Ti-species (Ti⁰, Ti²⁺, Ti–S, and Ti³⁺) as active species significantly lowered the dehydrogenation temperature and promoted the re-/dehydrogenation kinetics of MgH₂, and sulfur doping can effectively improve the stability of Ti⁰ and Ti³⁺, contributing to the improvement of cyclic stability of MgH₂. This study provides strategy for the construction of catalysts for hydrogen storage materials.

Magnesium hydride (MgH₂) is considered as an ideal hydrogen storage material with excellent hydrogen capacity, but the slow kinetics impedes its application. Herein, an efficient additive of V₂C MXene-anchored PrF₃ nanoparticles (PrF₃/V₂C) was synthesized, which presents excellent catalytic effect in improving the reversibility and stability of hydrogen storage in MgH₂. The initial dehydrogenation temperature of the 5 wt.% PrF₃/V₂C-containing MgH₂ (182 °C) is 105 °C lower than that of pure MgH₂, and 6.5 wt.% hydrogen is rapidly released from 5 wt.% PrF₃/V₂C-added MgH₂ sample in 6 min at 240 °C. In addition, 5 wt.% PrF₃/V₂C-containing MgH₂ sample possesses outstanding reversible hydrogen storage capability of 6.5 wt.% after 10 cycles of dehydrogenation and hydrogenation. Microstructure analysis shows that the introduction of Pr improves the stability of V-species (V⁰ and V²⁺) and O-species (lattice oxygen (O_L) and vacancy oxygen (O_V)) formed during ball milling, promotes the interaction between V-species and O-species, and enhances their reversibility, which contributes to the significant improvement in re/dehydrogenation reversibility and cycling stability of MgH₂. This study provides effective ideas and strategies for the purpose of designing and fabricating high-efficient catalysts for solid-state hydrogen storage materials.

The defect-free structure of Mo-based materials is a “double-edged sword”, which endows the material with excellent stability, but limits its chemical versatility and application in electrochemical hydrogen evolution reaction (HER). Carbon doping engineering is an attractive strategy to effectively improve the performance of Mo-based catalyst and maintain their stability. Herein, we report a cross-linked porous carbon-doped MoO₂ (C–MoO₂)-based catalyst Ru/C–MoO₂ for electrochemical HER, which is prepared by the convenient redox solid-phase reaction (SPR) of porous RuO₂/Mo₂C composite precursor. Theoretical studies reveal that due to the presence of carbon atoms, the electronic structure of C–MoO₂ has been properly adjusted, and the loaded small Ru nanoparticles provide a fast water dissociation rate and moderate H adsorption strength. In electrochemical studies under a pH-universal environment, Ru/C–MoO₂ electrocatalyst exhibits a low overpotential at a current density of 10 mA cm⁻² and has a low Tafel slope. Meanwhile, Ru/C-MoO₂ has excellent stability for more than 100 h at an initial current density of 100 mA cm⁻².