Hydrogen behavior in Mg+-implanted graphite

A graphite wafer has been implanted with Mg+ to produce a uniform Mg concentration. Subsequent H+ implantation covered the Mg+-implanted and -unimplanted regions. Ion-beam analysis shows a higher H retention in graphite embedded with Mg than in regions without Mg. A small amount of H diffuses out of the H+-implanted graphite during thermal annealing at temperatures up to 300 °C. However, significant H release from the region implanted with Mg+ and H+ ions occurs at 150 °C; further release is also observed at 300 °C. The results suggest that there are efficient H trapping centers and fast pathways for H diffusion in the Mg+-implanted graphite, which may prove highly desirable for reversible H storage.