Superior synergistic effect derived from MnTiO3 nanodiscs for the reversible hydrogen storage properties of MgH2

Abstract

Herein, nanodisc-like MnTiO3 was successfully prepared via a hydrothermal method, and for the first time, the MnTiO3 nanodiscs were doped into magnesium hydride (MgH2) for the study. In the first dehydrogenation cycle, MgH2-8 wt% MnTiO3 showed a low onset hydrogen release temperature of 202 °C, while MnTiO3 was transformed into Mg6MnO8 and TiOx by reaction with MgH2, which played a real catalyst in the subsequent reaction. The composite system could instantly absorb 4.79 wt% H2 in 100 s at 150 °C and rapidly release about 5.71 wt% H2 in 500 s at 300 °C. The Kissinger plot revealed that the dehydrogenation activation energy dropped to 72.06 kJ/mol, which was significantly lower than that of as-milled MgH2. Moreover, after 50 isothermal cycles, the composite system still has an excellent capacity retention rate of 94.4 %. Compositional and structural analysis indicated that the in situ formation of TiOx and Mg6MnO8 during dehydrogenation provided a multivalent multielement catalytic surrounding that accelerated the H atoms adsorption and dissociation, yielding a better kinetic property of MgH2.