Structural and H2 sorption properties of MgH2–10 wt%ZrCrM (M = Cu, Ni) nano-composites

Magnesium and its hydride MgH2 are widely regarded as promising candidates for hydrogen storage materials due to its benefits of high gravimetric and volumetric capacity, excellent reversibility, abundance in the earth and a low cost. Much attention has been paid to improve its absorption/desorption kinetics, trying to make it useful for practical applications. To make composite of MgH2 with other hydrogen storage compounds is an effective method to improve the hydrogen storage properties. In this study nano-composite of MgH2 with ZrCrCu alloy was prepared using high energy ball-milling for 5 h under Ar atmosphere. Microstructure and morphology of the composites were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM). XRD patterns show that no alloy formation between MgH2 and elements of the alloys takes place during milling. Different morphology of the powders as-milled and after cycling was observed by SEM. Pressure–composition isotherms of these composites have been obtained in the pressure range 0.1–10 bar at 275 and 300 °C. The absorption/desorption kinetics data have been analyzed using pressure 0.1–5.0 bar at 275 and 300 °C to understand the mechanism of the hydriding/dehydriding reaction processes. A comparison of these results has been attempted with our previous published results of MgH2–10 wt%ZrCrNi in order to find the better composite for storage applications. It is observed by DSC curves that the onset temperature of hydrogen desorption is decreased for MgH2–10%ZrCrNi in comparison to MgH2 which further decreased for MgH2–10%ZrCrCu. However, little loss in hydrogen absorption/desorption capacity is also observed for ZrCrCu composite in comparison to that of ZrCrNi composite.