Catalytic effects of V- and O-species derived from PrF₃/V₂C for efficient hydrogen storage in MgH₂

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.