Hydrogen storage properties of Mg-Li-Al composite system doped with Al2TiO5 catalyst for solid-state hydrogen storage

Abstract

A systematic investigation was performed on the 4MgH2 + LiAlH4 destabilized system with the inclusion of 5 wt% Al2TiO5 that was prepared by a ball milling process, and the hydrogen sorption performances were studied for the first time. A great advancement of the onset dehydrogenation temperature and de/rehydrogenation kinetics of 4MgH2 + LiAlH4 composite was achieved by doping Al2TiO5 to the composite. For the first and second desorption stages, the 4MgH2 + LiAlH4 + 5 wt% Al2TiO5 composite began to liberate hydrogen at 85 °C and 230 °C. In comparison, the undoped system commenced to liberate hydrogen at 120 °C and 270 °C, which were 35 °C and 10 °C lower, respectively when contrasted with the undoped composite. For the rehydrogenation kinetics, about 1.9 wt% hydrogen was absorbed within 5 min for the 5 wt% Al2TiO5-doped 4MgH2 + LiAlH4 system, whereas the neat sample only absorbed about 1.2 wt% hydrogen under similar conditions. As for the dehydrogenation kinetics, 4MgH2 + LiAlH4 + 5 wt% Al2TiO5 composite desorbed 1.7 wt% hydrogen within 10 min of desorption, while the 4MgH2 + LiAlH4 system released 0.8 wt% hydrogen in the same time frame. The apparent activation energy for the MgH2-relevant decomposition decreased from 121 kJ/mol (4MgH2 + LiAlH4 system) to 102 kJ/mol, after 5 wt% Al2TiO5 was introduced into the destabilized system. The decline in particle size also enhance the hydrogen storage behaviors. The synergistic effect of Al2TiO5 on the hydrogen storage behavior of 4MgH2 + LiAlH4 sample is attributed to the formation of new species of TiH2, AlTi2 and LiTi2O4 after ball milling and heating process, which acted as a real catalyser in the 4MgH2 + LiAlH4 + 5 wt% Al2TiO5 destabilized system.