| Summary: | A thorough investigation on hydrogen desorption of MgH2 and its reversibility with the focus on effects of a catalyst (TiCl3, TiO2, ZrCl4, and ZrO2) were reported. The experiments were carried out using a Sievert’s type apparatus. The reaction kinetics and the phase transformation behaviours were examined using a differential scanning calorimeter (DSC) and an X-ray diffractometer (XRD). It was found that the catalysts play an important role in facilitating smaller MgH2 crystallite size formation during ball-milling and accelerating hydride formation during the subsequent hydrogen absorption cycles resulting in the hydrogen desorption and reversibility enhancement of MgH2. Doping with ZrCl4 resulted in the smallest MgH2 crystallite size. That, in turn, resulted in the lowest hydrogen desorption temperature and the highest amount of released hydrogen in the first desorption. However, TiO2 was identified as the best catalyst because doping with TiO2 provided the highest amount of reversible hydrogen (~10% capacity drop from initial cycle).
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