Fully reversible hydrogen absorption and desorption reactions with Sc(Al1−xMgx), x=0.0, 0.15, 0.20

The hydrogen storage properties of Sc(Al_1−xMg_x), x=0.0, 0.15, 0.20, have been studied by X-ray powder diffraction, thermal desorption spectroscopy, pressure-composition-isotherms and scanning electron microscopy techniques. Hydrogen is absorbed from the gas phase at 70 kPa and 400 °C under the formation of ScH₂ and aluminium with magnesium in solid solution. The reaction is fully reversible in vacuum at 500 °C and shows the hydrogenation-disproportionation-desorption-recombination (HDDR) behaviour. The activation energy of desorption was determined by the Kissinger method to 185 kJ/mol. The material is stable up to at least six absorption-desorption cycles and there is no change in particle size during cycling.