Chemical Structure of Oxidized Multilayer Epitaxial Graphene: A Density Functional Theory Study

Density functional theory calculations are carried out to model the structure and interpret recent X-ray photoelectron spectroscopy measurements of graphene oxide films obtained by Hummers oxidation of multilayer graphene grown epitaxially on silicon carbide. The confrontations between theory and experiment are used to gain insight into the nature and fraction of the oxygen functional groups present in the oxide films. The study shows that this type of graphene oxide films includes small amounts of intercalated water molecules, ether groups, and doubly oxidized carbon species and that the oxidized graphene sheets encompass a disordered and homogeneous distribution of epoxide and hydroxyl species. The results of our spectral analysis are corroborated by a study of the energetic stability of water in this form of graphene oxide.