Additions of fluorine atoms to the surfaces of graphene Nanoflakes:A density functional theory study

Abstract

The electronic states and band gaps of carbon materials such as graphene, fullerene, and carbon nanotubes are strongly affected by radical addition. In the present study, the reactions of graphene nanoflakes with fluorine (F) atoms were investigated by density functional theory (DFT) in order to elucidate the nature of the bonding between the F atoms and the graphene nanoflakes. Graphene nanoflakes composed of 4–37 benzene rings were used as graphene models. The present calculations reveal that F atoms react with graphene surfaces and bind directly to carbon atoms to form strong C–F bonds. The binding sites are locally Cδ+-Fδ– polarized and have large dipole moments. The binding energy of F to graphene was calculated to be 30 kcal/mol, which is 1.5 times larger than that for the addition of hydrogen. Fluorine atoms also add to these surfaces without activation barriers, which is very different to hydrogen-addition reactions that have barriers of 5–6 kcal/mol. The electronic states of the fluorinated graphenes are discussed on the basis of the theoretical results.