Hydrogen sorption properties of a MgH2–10 wt.% graphite mixture

We present an analysis of the hydrogen absorption and desorption properties of a MgH2–10 wt.% graphite mixture prepared by reactive mechanical milling. The analysis is based on isothermal hydriding and dehydriding kinetic measurements and calorimetry experiments. The studied samples contained different hydrogen contents. From the characteristics of the sorption curves several features of the hydriding and dehydriding processes are identified. Additionally, the role of graphite in hydrogen sorption is analyzed.

Research highlights▶ H sorption kinetics of a MgH2-C mixture studied by volumetric and DSC experiments. ▶ H absorption and desorption with different hydrogen initial contents. ▶ H desorption controlled by nucleation and growth, and by the surface. ▶ H absorption proceeds without the formation of a uniform hydride layer. ▶ C does not change the rate controlling steps; it only increases the sorption rates.