A density functional theory study on the carbon defect in a graphene nano-flake surface promoting hydrogenation

The functionalization of graphene surfaces by covalent bonds has attracted much attention. Hydrogenated graphene exhibits ferromagnetism, and the degree of hydrogenation on the graphene surface allows for tuning the band gap. In this study, to elucidate the effect of defects in graphene hydrogenation, we investigated defective graphene wherein one carbon atom was removed from the central region of graphene nano-flake, by density functional theory. Hydrogenation of a graphene nano-flake by electrophilic addition in the gas phase is an exothermic reaction only when defects exist. The activation energy of defective graphene nano-flake hydrogenation is approximately 25 kcal mol[?]1 lower than that of the normal graphene one due to the involvement of the defect in surface distortion and transition state stabilization. The results obtained suggest that the hydrogenation of a graphene surface can be controlled by carbon defect.