Engineering graphene by oxidation: A first-principles study

Graphene epoxide, with oxygen atoms lining up on pristine graphene sheets, is investigated theoretically here using first-principles calculations. Two distinct phases - metastable clamped and stable unzipped structures - are observed consistent with experimental observations. In the clamped structure, oxygen atoms form a regular lattice on the graphene sheet. In the unzipped phase, an epoxy group breaks the lower sp² bond and modifies the mechanical and electronic properties of graphene remarkably. The foldable epoxy ring structure reduces its Young's modulus by 42.4%, while leaving the tensile strength almost unchanged. The perturbation of epoxidation on the band structures depends on the density and symmetry of oxidation. These results pave the way for oxidation-based engineering of graphene-related materials.