Improvement of hydrogen sorption properties of MgH2 with various sizes and stoichiometric compositions of TiC

Nano TiC powders having various sizes (50 nm, 130 nm, 300 nm and 600 nm) were added to MgH2 by high-energy ball milling to improve the hydrogenation properties of MgH2. The amount of hydrogen desorption/absorption of MgH2 catalyzed with TiC was slightly decreased, but MgH2 with 1 mol% TiC showed considerable catalytic effects on both the dehydrogenation and hydrogenation kinetics of MgH2. MgH2 with 50 nm TiC had the best absorption/desorption kinetics of MgH2 and the highest cyclic performance, desorbing about 6.2 wt.% H2 within about 20 min and absorbing more than 90% of hydrogen capacity within 5 min at 300 °C. The size of TiC was the important factor in inducing the catalytic effect, but the change of TiC composition was not as important as the particle size. Because by changing of particle sizes of TiC led to significant progress of dehydrogenation, but there was neither improvement of hydrogenation properties nor reaction kinetics by variation of TiC composition. X-ray diffraction analysis confirmed that nano-sized TiC remained stable with MgH2 after five cyclic tests in accordance with the prediction of thermodynamic calculation.