Enhanced hydrogen storage performance of destabilized 4MgH2-Li3AlH6 system doped with Co2NiO nanopowder

In this paper, the hydrogen storage properties and reaction mechanism of the destabilize MgH2-Li3AlH6 (4:1) system doped with 10 wt.% of Co2NiO were investigated for the first time. Temperature-programmed-desorption results showed that the addition of 10 wt.% of Co2NiO to the 4MgH2-Li3AlH6 composite improved the onset desorption temperature to 125 °C and 230 °C for the first two dehydrogenation stages. The temperatures were reduced to about 65 °C and 30 °C compared to un-doped composite. The rehydrogenation and dehydrogenation kinetics of 4MgH2-Li3AlH6 composite doped with 10 wt.% Co2NiO were also enhanced significantly compared to un-doped composite. The activation energy for the hydrogen desorption decreased after 10 wt.% of Co2NiO was added, which was 124 kJ/mol compared to un-doped 4MgH2-Li3AlH6 composite which was 149 kJ/mol. X-ray diffraction analysis showed the new phase formation of Co1.29Ni1.71O4 and Al-Ni in the doped composite after the dehydrogenation and rehydrogenation processes. It was believed that these two compounds acted as a catalyst in the 4MgH2-Li3AlH6-10 wt.% Co2NiO composite which may promote the interaction of MgH2 and Li3AlH6. The reduction of particle's size due to the presence of Co2NiO may also accelerated the hydrogen sorption performance of the MgH2-Li3AlH6 composite system.