Density functional theory study of graphite oxide for different oxidation levels

Abstract

Graphite oxide constitutes a hexagonal carbon network with oxygen atoms in carbon-oxide ether ring formations and hydroxyl molecules. We have studied graphite oxide with a first-principles density functional theory calculation for different oxidation levels. The oxygen atoms form 1,2-ether groups (epoxides) on the carbon grid, with on the adjacent carbon atoms, but at the opposite side of the carbon plane, the hydroxyl molecules. Graphite oxide cannot have 1,3-ether oxygens because of the higher formation energy. The transverse wrinkling of the carbon grid is about $0.5\text{ }\text{\AA{}}$, mostly due to the deformation around the hydroxyl bonds, yet the in-plane lattice axes retain the hexagonal features of graphene. A stable graphite oxide structure requires hydroxyl molecules to relax the tension on the carbon grid from the 1,2-ether oxygens. At a low degree of oxidation, graphite oxide is a semiconductor, but when the oxidation is saturated, it turns into an insulator.