In-Situ TEM Observation for Dehydrogenation Mechanism in MgH_2 with Catalyst

摘要

We carried out in-situ observation on the catalytic effect of Nb_2O_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_2O_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_2O_5. This result suggested that the dehydrogenation could proceed with hydrogen diffusion from MgH_2 through Mg phase to the boundary.