Microscopic study on hydrogenation mechanism of MgH2Catalyzed by Nb2O5

Abstract

We propose the microstructural change model of magnesium hydride catalyzed by Nb2O5during hydrogenation. The ball-milled composites, MgH2and 1 mol% Nb2O5, were dehydrogenated and then rehydrogenated for varied time at room temperature under 0.1 MPa H2atmosphere. The crystallite size of Mg and MgH2was evaluated by powder X-ray diffraction (XRD) measurement and confirmed by transmission electron microscopy (TEM) observation. The crystallite size of generated MgH2was smaller than that of Mg and did not change significantly with increasing time of hydrogenation. It is suggested that the number density of MgH2crystallites increases during the hydrogenation process.