Hydrogen cycling properties of xMg-Fe materials (x: 2, 3 and 15) produced by reactive ball milling

This work deals with the hydrogen cycling properties of xMg-Fe (x: 2, 3 and 15) elemental powder mixtures produced via low energy ball milling under hydrogen atmosphere at room temperature. The cycling process is carried out at constant temperature of 375 °C in a closed loop device. The evolution of both hydrogen storage capacity and absorption kinetic behavior are monitored during pressure cycling. Changes induced by cycling are characterized via scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and particle size distribution (PSD). All studied materials lost part of their hydrogen storage capacity during hydrogen cycling. This capacity reduction results from a combination of two effects: Mg evaporation and the formation of Mg2FeH6 which is stable at the experimental conditions. While the hydrogenation rates are not affected, the dehydrogenation kinetic properties of the materials are influenced by the cycling process.