Highly dispersed metal nanoparticles on TiO2 acted as nano redox reactor and its synergistic catalysis on the hydrogen storage properties of magnesium hydride

In this paper, we have synthesized highly dispersed Co metal nanoparticles with the particle size about 5–10 nm on TiO 2 (25–50 nm) for the first time through an extremely facile solvothermal method . It is supposed that the synthesized Co/TiO 2 composite can combine the catalytic advantage of both Co and TiO 2 , exhibiting the superior catalytic effect on the hydrogen de/absorption properties of MgH 2 . The experimental data confirmed the above supposition and demonstrated that Co/TiO 2 additive highly enhances the hydrogen de/absorption kinetics of MgH 2 as compared to separate Co or TiO 2 additive. Specifically, the MgH 2 Co/TiO 2 composite begins to desorb hydrogen at about 190 °C with a low apparent activation energy of 77 kJ/mol. Besides, the MgH 2 Co/TiO 2 composite has a desorption peak temperature of 235.2 °C, which is 53.2, 94.2 and 132.2 °C lower than that of MgH 2 TiO 2 (288.4 °C), MgH 2 Co (329.4 °C) and ball-milled MgH 2 (367.4 °C). Moreover, MgH 2 Co/TiO 2 composite also exhibits low temperature rehydrogenation properties, which can absorb 6.07, 5.56 and 4.24 wt% H 2 within 10 min at the temperature of 165, 130 and 100 °C, respectively. It is supposed that such excellent hydrogen desorption properties and low desorption energy barrier of MgH 2 Co/TiO 2 composite are mainly ascribed to the novel synergistic catalytic effects of Co and TiO 2 . Herein, we propose a novel catalytic mechanism and think that Co/TiO 2 acts as “nano redox reactor”, which can facilitate the dissociation and recombination process of hydrogen, thus reducing the reaction energy barrier and enhancing the de/rehydrogenation of MgH 2 .