Inclusion of CoTiO₃ to ameliorate the re/dehydrogenation properties of the Mg–Na–Al system

For the first time, the MgH₂–NaAlH₄ (ratio 4:1) destabilized system with CoTiO₃ addition has been explored. The CoTiO₃-doped MgH₂–NaAlH₄ sample begins to dehydrogenate at 130 ℃, which is declined by 40 ℃ compared to the undoped MgH₂–NaAlH₄. Moreover, the de/rehydrogenation kinetics characteristics of the CoTiO₃-doped MgH₂–NaAlH₄ were greatly ameliorated. With the inclusion of CoTiO₃, the MgH₂–NaAlH₄ composite absorbed 5.2 wt.% H₂, higher than undoped MgH₂–NaAlH₄. In the context of dehydrogenation, the CoTiO₃-doped MgH₂–NaAlH₄ sample desorbed 2.6 wt.% H₂, almost doubled compared to the amount of hydrogen desorbed from the undoped MgH₂–NaAlH₄ sample. The activation energy obtained by the Kissinger analysis for MgH₂ decomposition was significantly lower by 35.9 kJ/mol than the undoped MgH₂–NaAlH₄ sample. The reaction mechanism demonstrated that new phases of MgCo and AlTi₃ were generated in situ during the heating process and are likely to play a substantial catalytic function and be useful in ameliorating the de/rehydrogenation properties of the destabilized MgH₂–NaAlH₄ system with the inclusion of CoTiO₃.