First-principles calculations on O-atom diffusion on fluorinated graphene

Fluorination of graphene is one of the most effective methods to improve the corrosion protection of graphene coatings. In this paper, the diffusion and penetration behaviors of O atoms on fully fluorinated graphene (CF) and partially fluorinated graphene (C4F) were investigated using the NEB transition state search method. The effects of F atoms on the corrosion resistance of fluorinated graphene films were analyzed either. The results show that the adsorption of F atoms can effectively inhibit the diffusion of O atoms on graphene. On C4F, the F atoms are distributed in a para-top position, which greatly increases the surface diffusion energy barrier of O atoms. Moreover, it is difficult for the adsorbed O atoms to diffuse to different sp2 C rings through the obstruction of F atoms. The energy barrier of the horizontal diffusion of O atoms even reaches 2.69 eV in CF. And with the increase of F atoms, the stable structure of graphene is gradually destroyed, the barrier ability of C-atom layer for penetration behaviors of O atoms is greatly reduced. Furthermore, the interfacial adhesion work of pure graphene, CF and C4F films with Cu(111) surfaces were calculated, as well as the electronic structures of the composite interface using first-principles calculations. The interfacial adhesion work of the Cu/G, Cu/C4F and Cu/CF interfaces are 2.626J/m2、3.529J/m2and 3.559J/m2, respectively. The calculations show that the bonding of C4F and C4F with Cu substrate are more strong than pure graphene with Cu substrate, and the interfacial adhesion work increase with increasing of F atom adsorption concentration. The calculation of the density of states also conform stronger interaction between Cu and C atoms of the Cu/C4F interface than that of the Cu/CF interface. Bader charge analysis show increased charge transfer at both the Cu/C4F and Cu/CF interfaces comparing with the Cu/G interface, and Cu/C4F interface has more charge transfer, in which Cu-C bonds are formed.