Excellent catalysis of TiO2 nanosheets with high-surface-energy {001} facets on hydrogen storage properties of MgH2

摘要： Transition metal compound is one of the highly efficient catalysts in improving the reaction kinetics of hydrogen storage materials. Among all the transition metal, titanium and its compounds show great catalytic effect on magnesium hydride. In this paper, TiO2 nanosheets with exposed {001} facets were synthesized and doped into MgH2 for the first time. The TiO2 nanosheets (NS) doped MgH2 shows superior kinetic performance and lowest desorption temperature. The onset temperature of MgH2 + 5 wt% TiO2 NS to release hydrogen is 180.5 °C and the corresponding peak temperature is 220.4 °C, which are greatly lower than those of pure MgH2 and also distinctly lower than those of MgH2 + 5 wt% TiO2 nanoparticles (NP). For isothermal dehydrogenation analysis, the MgH2 + 5 wt% TiO2 NS can release 6.0 wt% hydrogen within 3.2 min at 260 °C and desorb 5.8 wt % hydrogen within 6 min at 240 °C. It is worth noting that the MgH2 + 5 wt% TiO2 NS can even release 1.2 wt% hydrogen at a temperature as low as 180 °C within 300 min. The hydrogenation kinetics of MgH2 + 5 wt% TiO2 NS is also greatly improved, which could absorb hydrogen within only a few seconds at the mild temperature. It can uptake 3.3 wt% hydrogen at 50 °C and 5.4 wt% at 100 °C within 10 s. It is demonstrated that the tremendous enhancement in reaction kinetics of MgH2 can be ascribed to the nanometer size and highly active {001} facets of anatase TiO2. The higher average surface energy can significantly reduce the hydrogen desorption activation energy of MgH2 to 67.6 kJ/mol, thus easily improves the hydrogen desorption properties.