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

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 TiO_x 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 TiO_x 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.