Hydriding behavior of Mg-50 wt% ZrCrFe composite Prepared by high energy ball milling

Magnesium hydride has a high theoretically storage capacity, which amounts to 7.6 wt%. It is therefore a promising candidate for hydrogen storage applications. However, its major drawback is its high desorption temperature of well over 300 °C, which is related to the high stability of the Mg–H bonds and expressed in the high enthalpy of hydride formation (77 kJ/mol). The preparation of Mg composites with other hydrogen storage compounds is an effective method to improve the hydrogen storage properties of Mg. Thus we prepared Mg-50 wt% ZrCrFe alloy composite by high energy ball milling under argon atmosphere. X-ray diffraction (XRD) studies on the composite before and after hydriding cycles suggest no intermetalic phase is formed between Mg and the elements of the alloy. The morphological studies carried on by Scanning Electron Microscope (SEM) technique suggest that the alloy particles are homogeneously distributed throughout the Mg surface. A particle reduction after hydrogenation is also visible. Hydriding/dehydriding properties of the composites are investigated by PCT measurements using a dynamic system. The maximum hydrogen capacity for this composite is found to be 4.5 wt%. The reaction kinetics have also been recorded in a temperature range from RT to 300 °C and the thermodynamic parameters calculated from Van’t Hoff plot. From the results it is found that the alloy reacts with hydrogen also when cooled to room temperature while at higher temperature it works as catalyst.

► Present paper describes the hydrogenation behaviour of Mg – 50 wt% ZrCrFe composite. ► The total effective capacity of this composite was found to be 4.5 wt %, which is higher than any previous similar works reported in the literature. ► At high temperature ZrCrFe phase was found to act as catalyst enhancing Mg hydrogen adsorption/desorption properties. ► When cooled to room temperature ZrCrFe is converted to the hydriding phase, thus contributing to the total hydrogen capacity of the composite.