STRUCTURAL EVOLUTION OF A Mg-C COMPOSITE OVER 1000 H2 STORAGE CYCLES

With its high capacity (7.6 wt%), magnesium is a promising material for high temperature hydrogen storage applications [1]. To date, few studies have systematically tracked the morphological evolution of a material over a large number of hydrogen (de)sorption cycles. A Mg-C composite was prepared and exposed to 1000 hydrogen (de)sorption cycles. The experiment was interrupted at several points during cycling to retrieve a small aliquot of powder in order to characterize the crystallographic and morphological changes that were taking place in the material. The material demonstrated good capacity retention until about 700 cycles had been completed, at which point the kinetics of hydrogen (de)sorption began to slow. This could be explained by grain growth and particle densification observed in the material on extended cycling.