Enhanced hydrogen storage properties of MgH 2 catalyzed with carbon-supported nanocrystalline TiO 2

Abstract Carbon-supported nanocrystalline TiO2 (TiO2@C) shows good catalytic activity in the hydrogen storage reaction of MgH2. Adding a small amount of carbon-supported nanocrystalline TiO2 remarkably reduces the dehydrogenation operating temperatures because the MgH2-10 wt% TiO2@C sample starts releasing H2 at 205 °C, which is 95 °C lower than that of pristine MgH2. At 300 °C, the 10 wt% TiO2@C-containing sample rapidly releases 6.5 wt% hydrogen within 7 min. More importantly, the dehydrogenated 10 wt% TiO2@C-containing sample takes up hydrogen even at room temperature and under a hydrogen pressure of 50 bar, and approximately 6.6 wt% hydrogen is absorbed within 10 min at 140 °C. Kinetic measurements reveal a 30% and 50% reduction in the apparent activation energy of the dehydrogenation and hydrogenation of MgH2, respectively, with the presence of 10 wt% TiO2@C additive. Density functional theory calculations present the extended bond lengths and the reduced bond strengths for Mg-H bonding when MgH2 adsorbs on the TiO2 clusters, which is responsible for the reduced de-/hydrogenation temperatures of the TiO2@C-containing MgH2.