Analysis of the strong propensity for the delocalized diamagnetic π electronic structure of hydrogenated graphenes

The conformation and electronic structure of hydrogen-treated graphenes are investigated using the density-functional theory (DFT) method. We show that the overall energetics of the hydrogen chemisorption configuration can be analyzed with two energy components: the electronic pairing effect in the hyper-conjugated π electron network and the strain effect in the C-C bond at the boundary between sp3- and sp2-bonded regions. Some unpaired hydrogenation configurations can show magnetic ground states, but these were found to be unstable. The least strained paired configurations strongly favored the delocalized π electronic states. This suggests that appropriate annealing following a hydrogen plasma treatment of graphene can lead to a semiconducting state with a stable finite bandgap.