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

Abstract

Fluorination of graphene is one of the most effective methods to improve the corrosion protection of graphene coatings. In this work, the diffusion and penetration behaviors of O atoms on fully fluorinated graphene (CF) and partially fluorinated graphene (C₄F) are investigated by using the method of searching for NEB transition state . The effects of F atoms on the corrosion resistance of fluorinated graphene films are also analyzed <i>r</i>. 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 ability of C-atom layer to bar the penetration behaviors of O atoms decreases greatly. Furthermore, the interfacial adhesion work of pure graphene, CF and C₄F films with Cu(111) surfaces are calculated, as well as the electronic structures of the composite interface are investigated by using first-principles calculations. The interfacial adhesion work of the Cu/G, Cu/C₄F and Cu/CF interfaces are 2.626 J/m², 3.529 J/m² and 3.559 J/m², respectively. The calculations show that the bonding of C₄F and C₄F with Cu substrate are stronger than pure graphene with Cu substrate, and the interfacial adhesion work increases with the augment of F atom adsorption concentration. The calculation of the density of states also conforms that the interaction between Cu and C atoms of the Cu/C₄F interface is stronger than that at the Cu/CF interface. Bader charge analysis shows that the charge transfer at the Cu/C₄F interface and the Cu/CF interface increase comparing with that at the Cu/G interface, and Cu/C₄F interface has more charge transfer, in which Cu—C bonds are formed.