Crystal defect analysis and surface characteristics of produced by hydriding combustion synthesis

The mechanism of the high activity of Mg 2 NiH 4 produced by the process of hydriding combustion synthesis (HCS) was discussed for the first time based mainly on the crystal defects and surface characteristics examined by means of high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). A large number of crystal defects (lattice distortions, dislocations, stacking faults and microtwins) observed in the as-dehydrogenated product of Mg 2 NiH 4 and an outmost layer of Mg ( OH ) 2 , instead of MgO determined on the surface of the as-synthesized Mg 2 NiH 4 , as well as a large amount of fresh surfaces in Mg 2 Ni particles that was generated in the dehydriding process of the as-synthesized Mg 2 NiH 4 prior to the first hydrogenation were revealed and considered as the intrinsic reasons contributing to the high activity of Mg 2 NiH 4 produced by the process of HCS. These results are helpful to control and improve the hydrogen storage properties of the HCS product further.