Facile construction of Mxene-supported niobium hydride nanoparticles toward reversible hydrogen storage in magnesium borohydride

The facile construction of nanoscale NbH_x supported by Ti₃C₂ (NbH_x@Ti₃C₂) was achieved using facile ball milling strategy to improve the hydrogen desorption kinetics and reversibility of magnesium borohydride (Mg(BH₄)₂). The doping of 30 wt% NbH_x@Ti₃C₂ catalyst reduced the onset dehydrogenation temperature of Mg(BH₄)₂ to 71.2 °C. Additionally, the Mg(BH₄)₂ + 30NbH_x@Ti₃C₂ composite achieved remarkable hydrogen release of over 9.2 wt% at a temperature as low as 230 °C, indicating unexpected dehydrogenation kinetics. Moreover, the reversibility of NbH_x@Ti₃C₂ doped Mg(BH₄)₂ was retained to more than 4.2 wt% after four cycles, which was increased by 68% compared to that of undoped Mg(BH₄)₂. The strong catalysis of NbH_x@Ti₃C₂ catalyst could be attributed to the synergistic effect of NbH_x and Ti₃C₂ in hydrogen spillover and diffusion. NbH_x acted as a “hydrogen pump” for effective hydrogen spillover, while Ti₃C₂ created numerous diffusion channels for hydrogen dissolution and provided the active catalytic site to facilitate the re/dehydrogenation of Mg(BH₄)₂.