Nb-V induced cation vacancy for regulating the de/rehydrogenation kinetics of MgH2

Magnesium hydride (MgH 2 ) for hydrogen storage suffers from high thermodynamic stability and slow kinetics. Vacancy engineering has emerged as an effective strategy to improve its performance. Herein, vanadium-deficient VSe 2 nanoflowers assembled from nanosheets were fabricated via Nb doping, which introduced cation vacancies acting as efficient catalysts for MgH 2 . MgH 2 +10 wt% Nb-doped VSe 2 exhibits greatly enhanced kinetics compared with pure MgH 2 and undoped VSe 2 -added MgH 2 . At 275 °C, it releases ∼6.11 wt% H 2 within 300 s and retains 5.66 wt% after 60 cycles. The improved performance stems from three synergistic effects: electron-rich interfaces boosting H 2 dissociation, multivalent V 4+ /Nb 5+ accelerating electron transfer, and active phases (V, MgSe) providing more active sites and diffusion pathways. This study offers a valuable defect-engineering route for high-performance hydrogen storage catalysts.