Fibrous V/Nb bimetallic oxides with remarkable catalytic effect on hydrogen storage properties of MgH2

MgH₂ is recognized as one of the most promising solid hydrogen storage materials; however, its practical application is confined by sluggish kinetics and stable thermodynamics. In this study, fibrous VNbO₅ was synthesized via electrospinning and subsequently introduced into MgH₂ through ball milling technology to enhance hydrogen storage properties. The addition of 7 wt% VNbO₅ give rise to the obvious decline in the initial dehydrogenation temperature of MgH₂, from 322.2 °C to 200.2 °C. At 300 °C, the modified composite exhibited rapid dehydrogenation, releasing approximately 6.43 wt% hydrogen within 8.1 min. Moreover, the fully dehydrogenated sample demonstrated the ability to absorb hydrogen at room temperature and absorbed 6 wt% H₂ at 200 °C within 16 s. The desorption activation energy of the MgH₂-7 wt% VNbO₅ composite was determined to be 75.32 ± 1.44 kJ/mol, representing an approximate 48.1% reduction compared to the 145.25 ± 2.14 kJ/mol of pure MgH₂. Furthermore, the system possessed remarkable cyclic stability, retaining 95.5% of hydrogen storage amount after 20 cycles. During the reaction process, VNbO₅ decomposed into low-valence state active catalytic species, including Nb₂O₅, NbO, Nb, VO₂, and V. The in-situ generation of this multi-element, multi-valence chemical environment synergistically enhanced hydrogen storage performance of MgH₂.