Remarkably Improved Hydrogen Storage Performance of MgH 2 Catalyzed by Multivalence NbH x Nanoparticles

Magnesium hydride is widely investigated because of its high hydrogen storage capacity. However, the unfavorable thermodynamic and kinetic barriers hinder its practical application. To ease these problems, three kinds of NbH x nanoparticles were prepared by wet-chemical methods and then introduced into MgH 2 for catalytically enhancing its hydrogen storage properties in this work. The results show that all the NbH x nanoparticles are effective in promoting the de-/rehydrogenation kinetics of MgH 2, and the three NbH x doped MgH 2 composites can desorb 7.0 wt % H 2 within 9 min at 300 °C while ball milled MgH 2 only releases 0.2 wt % H 2 in 9 min and 4.1 wt % H 2 even in 200 min. Interestingly, the significant hydrogen absorption by NbH x doped MgH 2 under lower temperature ranging from 50 to 100 °C was observed; thus, MgH 2 / c -NbH x sample can uptake about 4.0 wt % H 2 at 100 °C. It is found that the more disordered the structure and smaller the size of the NbH x particles, the better is the catalytic effect on hydrogen storage performances of MgH 2 . Analyses of XRD, XPS, and TEM results indicate that the NbH x remains stable in the ball milling and following de-/rehydrogenation process and act as active catalytic species in improving hydrogen storage performance of MgH 2 . Moreover, a mechanism is proposed to understand how the nanosized NbH x acted as charge transfer between Mg 2+ and H –, which contributes to the significantly improved hydrogen storage performances of MgH 2 . It is believed that the use of Nb-based nanoparticles as catalysts would greatly promote the development of the practical applications of MgH 2 for hydrogen storage.