The hydrogen storage performance of a 4MgH₂-LiAlH₄-TiH₂ composite system

The hydrogen storage performance of a 4MgH₂-LiAlH₄ composite system was greatly improved by adding TiH₂. The temperature-programmed release curve of the 4MgH₂-LiAlH₄-TiH₂ composite reflected that the onset temperature of dehydrogenation decreased remarkably to 54 °C from that of 4MgH₂-LiAlH₄ (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 4MgH₂-LiAlH₄, 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 4MgH₂-LiAlH₄. Isothermal hydrogenation curves and fitted lines from the Arrhenius equation demonstrated the enhancement of hydrogenation kinetics.