Hydrogenation Behaviors of MgHx-Graphene Composites by Reactive Mechanical Grinding

Abstract

In order to mitigate the disadvantage of the Mg hydrides, several studies have been conducted that have used MgHx intermixed with carbon. Graphene is a kind of carbon allotrope that is easily subject to a desorption reaction at low temperatures because such a reaction is exothermic. In this work, an MgHx-graphene mixture has been prepared by reactive mechanical grinding. The synthesized powder was characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and simultaneous thermogravimetric (TG) and differential scanning calorimetric (DSC) analyses. The hydrogenation behaviors were evaluated using a Sievert’s type automatic pressure-composition-temperature (PCT) apparatus without activation treatment. From the characteristics of the absorption kinetics and the curves observed, the role of graphene as a catalyst in hydrogen absorption was determined. According to the results of the PCI curve, the available hydrogen storage amounts for MgHx-5 wt% graphene composites had maximum values of 3.69, 5.09, and 5.72 wt% at 423, 523, and 623 K, respectively. Those values for MgHx-10 wt% graphene were 5.08, 5.45, and 5.83 wt% at 423, 523, and 673K, respectively.