Enhanced hydrogen storage properties of 4MgH2Â +Â 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.