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 sp~3- and sp~2-bonded regions. Some unpaired hydro-genation configurations can show magnetic ground states, but these were found to be unstable. The least strained paired configurations strongly favored the delocalized % 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.
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