In situ transmission electron microscopy study on microstructural changes in NbF5-doped MgH2 during dehydrogenation

Microstructural changes in NbF5-doped MgH2 during the dehydrogenation reaction (MgH2 → Mg + H2) have been investigated by in situ heating transmission electron microscopy. Nanocrystalline MgH2 shows fast hydrogen sorption kinetics, as well as a high density of defects induced by high-energy ball milling. Since the network-structured Nb layer covering Mg grains acts both as an impediment to grain growth of Mg and a gateway for hydrogen diffusion by forming metastable NbH1−x, the improved kinetics can be maintained during hydrogen cycling.