Effects of SnO2 on hydrogen desorption of MgH2

The hydrogen desorption properties of Magnesium Hydride (MgH2) ball milled with cassiterite (SnO2) have been investigated by X-ray powder diffraction and thermal analysis. Milling of pure MgH2 leads to a reduction of the desorption temperature (up to 60 K) and of the activation energy, but also to a reduction of the quantity of desorbed hydrogen, referred to the total MgH2 present, from 7.8 down to 4.4 wt%. SnO2 addition preserves the beneficial effects of grinding on the desorption kinetics and limits the decrease of desorbed hydrogen. Best tradeoff – activation energy lowered from 175 to 148 kJ/mol and desorbed hydrogen, referred to the total MgH2 present, lowered from 7.8 to 6.8 wt% – was obtained by co-milling MgH2 with 20 wt% SnO2.

► SnO2 addition during milling of MgH2 stabilizes the β-MgH2 phase.
► SnO2 acts as a lubricant during the milling of MgH2, limiting the hydrogen loss.
► H2 desorption temperature and activation energy are markedly decreased.