Improved hydrogen storage properties of Mg-Li-Al-H composite system by milling with Fe2O3 powder

A sample of Fe₂O₃-doped 4MgH₂-Li₃AlH₆ composite was prepared by the ball milling technique, and the hydrogen storage properties were investigated for the first time. Results showed that the addition of Fe₂O₃ powder reduced the decomposition temperature and improved de/hydrogenation kinetics compared with undoped 4MgH₂-Li₃AlH₆. The onset decomposition temperature for the Fe₂O₃-doped 4MgH₂-Li₃AlH₆ composite decreased by 75 °C compared with that of the undoped composite. For the sorption kinetics, a hydrogen absorption capacity of 2.4 wt% was reached after 60 min in the 10 wt% Fe₂O₃-doped 4MgH₂-Li₃AlH₆ composite, whereas the neat composite absorbed 2.3 wt% hydrogen under the same conditions. For desorption kinetics, the Fe₂O₃-doped 4MgH₂-Li₃AlH₆ sample released 2.5 wt% hydrogen under 10 min of dehydrogenation, but the neat 4MgH₂-Li₃AlH₆ composite only desorbed 2.0 wt% hydrogen within the same period. The apparent activation energy calculated by Kissinger analysis for hydrogen desorption decreased to 112.9 kJ/mol after Fe₂O₃ was added compared with the undoped composite, which was 145.4 kJ/mol. The X-ray diffraction analysis shows the formation new phase of Li₂Fe₃O₄ in the doped sample after ball milling processes that could act as the real catalyst in the Fe₂O₃-doped 4MgH₂-Li₃AlH₆ composite.