Synthesis and decomposition of Mg2FeH6 prepared by reactive milling

The direct synthesis of Mg2FeH6 by mechanical alloying in hydrogen atmosphere (‘reactive milling’) has been investigated using different high-energy ball milling conditions. Using planetary and vibration mills, the influence of milling temperatures of up to 250 °C and of the energy input during milling on the hydride formation has been studied. XRD and high resolution scanning electron microscopy were utilised to follow the structural evolution during hydride formation upon ball milling. Yield rates of up to 90 wt.% for Mg2FeH6 were achieved after optimising the synthesis conditions and Fe concentration. The decomposition of the hydride on desorption was then studied in dependence on synthesis conditions and initial Fe content. Gravimetric analysis was performed to characterise kinetics of absorption and desorption. The role of minor additions of platinum group metals (PGMs) was investigated with regards to kinetics and reversibility.