High-temperature hydrogen cycling properties of magnesium-based composites

High-temperature desorption kinetics and cyclic stability of MgH2-TM composites (TM=Fe, Co) were studied to investigate the feasibility of the composites as thermal energy storage materials. At 420 °C and 440 °C, the desorption kinetics of MgH2 can be significantly improved by adding 5 wt% of nanosize Fe or Co. At 420 °C, MgH2-Fe and MgH2-Co composites have excellent cyclic stability with a hydrogen storage capacity of 7.0 wt%. While cycling at 440 °C, the MgH2-Co shows a poor cyclic stability with a lower storage capacity of 5.0 wt%. The capacity loss is the result of formation of MgCo and Mg2CoH5 during the cycling process.