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 pi electron network and the strain effect in the C-C bond at the boundary between sp(3)- and sp(2)-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 pi 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. (C) 2011 Elsevier Ltd. All rights reserved.