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

The facile construction of nanoscale NbH x supported by Ti 3 C 2 (NbH x @Ti 3 C 2 ) was achieved using facile ball milling strategy to improve the hydrogen desorption kinetics and reversibility of magnesium borohydride (Mg(BH 4 ) 2 ). The doping of 30 wt% NbH x @Ti 3 C 2 catalyst reduced the onset dehydrogenation temperature of Mg(BH 4 ) 2 to 71.2 °C. Additionally, the Mg(BH 4 ) 2  + 30NbH x @Ti 3 C 2 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 @Ti 3 C 2 doped Mg(BH 4 ) 2 was retained to more than 4.2 wt% after four cycles, which was increased by 68% compared to that of undoped Mg(BH 4 ) 2 . The strong catalysis of NbH x @Ti 3 C 2 catalyst could be attributed to the synergistic effect of NbH x and Ti 3 C 2 in hydrogen spillover and diffusion. NbH x acted as a “hydrogen pump” for effective hydrogen spillover, while Ti 3 C 2 created numerous diffusion channels for hydrogen dissolution and provided the active catalytic site to facilitate the re/dehydrogenation of Mg(BH 4 ) 2 . Graphical abstract