Hydrogen storage in magnesium – metal mixtures: reversibility, kinetic aspects and phase analysis

The sorption capacity and kinetics of mechanically activated binary mixtures of Mg with nine different metals (Al, Cu, Fe, Mn, Mo, Sn, Ti, Zn, Zr) have been studied to determine whether these metals act as catalyzing/destabilizing agents in formation/decomposition of Mg hydrides. Identification of crystalline phases before and after the absorption/desorption processes assists our understanding of the different behaviors displayed by the studied compounds. Cu, Al and Zn take active part in Mg hydrogenation/dehydrogenation, but only the addition of Cu is actually effective in MgH2 destabilization, leading to a substantial decrease of the desorption temperature of this phase (down to 270 °C), and to an improved desorption kinetics. With the other metals, the hydrogen release usually occurs at a significant rate only above 320 °C and the kinetics of the absorption/desorption processes are slower than in the Mg/MgH2 system.