Enhanced hydrogen storage properties of magnesium by the synergic catalytic effect of TiH_1.971 and TiH_1.5 nanoparticles at room temperature

In order to improve the hydrogen sorption kinetics of Mg at room temperature, the Mg-9.2wt%TiH_1.971-3.7wt%TiH_1.5 nanocomposite is successfully prepared by hydrogen plasma-metal reaction (HPMR) method and hydrogenation/dehydrogenation at 673 K. The Mg nanoparticles are hexagonal in shape with the size in the range of 50-190 nm. The spherical Ti hydrides nanoparticles of about 13 nm are uniformly dispersed on the surface of Mg nanoparticles. During hydrogenation/dehydrogenation cycle, the Ti hydrides nanoparticles restrain the growth of Mg nanoparticles. The Mg-TiH _1.971-TiH_1.5 nanocomposite quickly absorbs 4.3 wt% H ₂ in 10 min at room temperature and reaches a saturation value of 5.0 wt% in 60 min. The apparent activation energies for hydrogen absorption and desorption are 12.5 and 46.2 kJ mol^-1, respectively. The improved kinetics and reduced activation energy are explained in terms of the nanostructure of Mg and the synergic catalytic effect of TiH_1.971- TiH_1.5 nanoparticles.