Catalysis derived from three-dimensionally ordered macroporous Nb2O5 towards the hydrogen storage performance of magnesium hydride

A three-dimensionally ordered macroporous (3DOM) Nb2O5 was successfully prepared via the colloidal crystal template method, which demonstrates a significant effect in enhancing the hydrogen storage performances of MgH2. 3DOM Nb2O5 presents an overall macroporous structure with a highly ordered overall arrangement and connected layers. As limiting domains influence of 3DOM structure, Nb2O5 nanoparticles ranging in size from 5 to 15 nm are encapsulated with the amorphous carbon layer. The MgH2-5 wt% 3DOM Nb2O5 MM 30 h composite can absorb 6.35 wt% H2 in 500 s at 175 °C and desorb 6.95 wt% H2 in 300 s at 300 °C. The unique Nb2O5 3DOM structure can provide more active sites and a larger contact area for the hydrogen ab/desorption of MgH2. The in situ formed NbHx can promote the dissociation and complexation of molecular hydrogen on its surface and induce the hydrogen boundary/interface diffusion along the Mg/MgH2 interface, thus facilitating the hydrogen ab/desorption reaction of MgH2. In addition, the binding energy transfer of Nb2O5 can be observed by XPS and the electron shift at the MgH2/Nb2O5 interface is further confirmed by the theoretical calculations, which can weaken the Mg-H bond and induce MgH2 to become unstable. This finding will provide ideas for the design and preparation of catalysts with special morphologies for Mg-based hydrogen storage materials.