In-Situ TEM Observation for Dehydrogenation Mechanism in MgH2 with Catalyst

We carried out in-situ observation on the catalytic effect of Nb(2)O(5) in MgH(2) by using a high voltage transmission electron microscope (HVEM). We synthesized two kinds of samples, which were prepared by ball milling and by hand mixing. In milled sample, Nb(2)O(5) was not confirmed from high resolution images, however, NbO was identified. As the temperature increased, the decomposition of MgH(2) proceeded, while Mg formed and grew. It suggested that NbO had the catalytic effect to promote the dehydrogenation of MgH(2). In mixed sample, which was prepared to clearly observe the boundary between the catalyst and Mg phase, it was revealed that the dehydrogenation started from the boundary of MgH(2) and Nb(2)O(5). This result suggested that the dehydrogenation could proceed with hydrogen diffusion from MgH(2) through Mg phase to the boundary.