On the possibility of hydrogen intercalation of graphite-like carbon materials - Electrochemical and molecular orbital studies

Graphite-like carbon materials were investigated to learn whether they form hydrogen-graphite intercalation compounds (H-GICs), which would be useful as hydrogen storage materials in rechargeable batteries. The ability of graphite-like materials to absorb hydrogen was examined with cyclic voltammetry (CV) and constant-current charge and discharge tests in 6 mol dm^-3 KOH. It was concluded that H-GICs did not form under our experimental conditions. In order to understand the difference between hydrogen and lithium ions in ability to form the intercalation compounds with graphite-like carbon materials, molecular orbital analyses were carried out. The results demonstrate that lithium-graphite intercalation compounds (Li-GICs) are stable because of the presence of lithium 2p-orbitals, whereas such stable graphite intercalation compounds do not form with hydrogen ions because no three-dimensional p-orbitals are available.