Reversible Metal-Hydride Transformation in Mg-Ti-H Nanoparticles at Remarkably Low Temperatures

We study the kinetics of hydrogen sorption in Mg-Ti-H nanoparticles prepared by gas phase condensation of mixed Mg-Ti vapors under a H 2 -containing atmosphere. Four samples with different Ti contents from 14 to 63 at.% Ti are examined in the 100–150 °C range. The hydrogen absorption kinetics coupled with the formation of MgH 2 can be described by a nucleation and growth model. The activation energy is in the range (Formula presented.) kJ/mol and the rate constant (at 150 °C) increases from (Formula presented.) s −1 to (Formula presented.) s −1 with increasing Ti content. Hydrogen desorption is well modeled by a sequence of surface-limited and contracting-volume kinetics, except at the highest Ti content where nucleation and growth is observed. The activation energy of surface-limited kinetics is (Formula presented.) /mol. The rate constant (at 150 °C) increases from (Formula presented.) s −1 to (Formula presented.) s −1 with the Ti content. These results open an unexplored kinetic window for Mg-based reversible hydrogen storage close to ambient temperature.