Graphitization of graphene oxide with ethanol during thermal reduction

Abstract

As an atypical reductant, ethanol has recently been considered for reducing the oxygen concentration and restoring the graphitic structure in multilayered graphene oxide (GO) during annealing [Su et al., ACS Nano2010, 4, 5285]. The reaction mechanism is, however, still not well understood, hindering progress in the use of GO. By combining density functional theory (DFT), ab initio molecular dynamics (MD) calculations, and in situ infrared absorption spectroscopy, the thermal evolution of both carbonyl and ether groups in multilayered GO is shown to vary dramatically upon individual intercalation of methanol, ethanol, and water molecules. In hydrated GO, bare etch holes are generated by thermal annealing, as evidenced by the evolution of carbon dioxide (CO 2) molecules. In contrast, the replacement of water by methanol or ethanol prevents defect enlargement during annealing. Furthermore, ethanol is found to repair the etch holes by facilitating the formation of new hexagonal carbon rings. Ab initio MD simulations map out the likely reaction pathways that are subsequently verified by DFT total energy calculations. The elucidation of the mechanism of etch hole healing in GO suggests new ways to tailor the structural and electronic properties of reduced GO (rGO) and graphene for a variety of applications requiring defect engineering. © 2012 American Chemical Society.