Evolution of reduced Ti containing phase(s) in MgH2/TiO2 system and its effect on the hydrogen storage behavior of MgH2

Abstract The present study aims to consolidate information regarding the catalytic reaction mechanism of MgH 2 /TiO 2 hydrogen storage system. Reduction of titania, resulting to evolution of a monoxide rock salt nanocrystalline phase was identified by in-situ X-ray diffraction (XRD) study of a 3 mol% TiO 2 additive mixed MgH 2 . Existence of homogeneously distributed Ti in a crystalline rock salt matrix was confirmed by combined analysis of X – ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and elemental chemical mapping techniques. Moreover, titanium in Ti 3+ and Ti 2+ valance states was confirmed by X - ray photoelectron spectroscopy (XPS). Differential scanning calorimetry (DSC) study proves that the reduced Ti oxide phases promote the low temperature dehydrogenation of MgH 2 . The present observations reiterate that the MgO rock salt layer existing in oxide additives loaded MgH 2 is not necessarily a barrier layer that blocks the diffusion of hydrogen.