The hydrogen storage performance of a 4MgH2LiAlH4TiH2 composite system

•The onset temperature of hydrogen release was decreased to 54 °C in 4MgH2LiAlH4TiH2 composite.•Additive TiH2 reduced the de/re-hydrogenation activation energies.•TiH2 was not involved in the reactions, but served as catalyst for composite's dehydrogenation.

The hydrogen storage performance of a 4MgH2LiAlH4 composite system was greatly improved by adding TiH2. The temperature-programmed release curve of the 4MgH2LiAlH4TiH2 composite reflected that the onset temperature of dehydrogenation decreased remarkably to 54 °C from that of 4MgH2LiAlH4 (100 °C). X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses indicated that TiH2 was not involved in the decomposition of either LiAlH4 or MgH2 or their interactions. In the ternary composite, TiH2 can be regarded as an effective catalyst for LiAlH4, Li3AlH6 and MgH2, of which the activation energies of dehydrogenation were reduced by 23.3 kJ/mol, 29.1 kJ/mol and 45.5 kJ/mol from those of 4MgH2LiAlH4, respectively. The rehydrogenation of those products at 350 °C cannot be fully integrated into their original phases, and the reversible capacity was ascribed only to the formation of MgH2. The activation energy of rehydrogenation of MgH2 was greatly decreased to 108.9 kJ/mol from 158.8 kJ/mol of 4MgH2LiAlH4. Isothermal hydrogenation curves and fitted lines from the Arrhenius equation demonstrated the enhancement of hydrogenation kinetics.