Enhanced hydrogen storage properties of 4MgH2 + LiAlH4 composite system by doping with Fe2O3 nanopowder

In this paper, the hydrogen storage properties and reaction mechanism of the 4MgH2 + LiAlH4 composite system with the addition of Fe2O3 nanopowder were investigated. Temperature-programmed-desorption results show that the addition of 5 wt.% Fe2O3 to the 4MgH2 + LiAlH4 composite system improves the onset desorption temperature to 95 °C and 270 °C for the first two dehydrogenation stage, which is lower 40 °C and 10 °C than the undoped composite. The dehydrogenation and rehydrogenation kinetics of 5 wt.% Fe2O3-doped 4MgH2 + LiAlH4 composite were also improved significantly as compared to the undoped composite. Differential scanning calorimetry measurements indicate that the enthalpy change in the 4MgH2–LiAlH4 composite system was unaffected by the addition of Fe2O3 nanopowder. The Kissinger analysis demonstrated that the apparent activation energy of the 4MgH2 + LiAlH4 composite (125.6 kJ/mol) was reduced to 117.1 kJ/mol after doping with 5 wt.% Fe2O3. Meanwhile, the X-ray diffraction analysis shows the formation of a new phase of Li2Fe3O4 in the doped composite after the dehydrogenation and rehydrogenation process. It is believed that Li2Fe3O4 acts as an actual catalyst in the 4MgH2 + LiAlH4 + 5 wt.% Fe2O3 composite which may promote the interaction of MgH2 and LiAlH4 and thus accelerate the hydrogen sorption performance of the MgH2 + LiAlH4 composite system.