| AVS 60th International Symposium and Exhibition | |
| Graphene and Other 2D Materials Focus Topic | Thursday Sessions |
| Session GR+AS+BI+PS+SS-ThA |
| Session: | Plasma Processing, Surface Chemistry, Functionalization, and Sensor Applications of 2D Materials |
| Presenter: | S.L. Weeks, Colorado School of Mines |
| Authors: | S.L. Weeks, Colorado School of Mines B. Narayanan, Colorado School of Mines B.N. Jariwala, Colorado School of Mines B. Macco, Eindhoven University of Technology, Netherlands J.W. Weber, Eindhoven University of Technology, Netherlands M.C.M. van de Sanden, Eindhoven University of Technology; DIFFER, Netherlands C.V. Ciobanu, Colorado School of Mines S. Agarwal, Colorado School of Mines |
| Correspondent: | Click to Email |
Reduction of graphene oxide (GO) has recently generated intense research interest due to the possibility of using this method to inexpensively produce large quantities of graphene. Current reductive processes rely on thermal or chemical removal of oxygen functional groups from the surface. While reduction has been demonstrated, a certain fraction of residual oxygen remains after processing with current techniques. Furthermore, the use of high process temperatures in the reduction of GO leads to the generation of defects through the loss of carbon atoms from the basal plane of graphene. The ultimate improvement in the electronic, optical, or mechanical properties of graphene that can be achieved through reduction of GO is limited by defect formation and the residual oxygen remaining after reduction through present reported methods. Here, we report the facile removal of oxygen functional groups from the surface of GO through reduction in a carbon monoxide atmosphere. Common oxygen-containing functional groups on the basal plane of GO (epoxides, hydroxyls, and ketone pairs) are removed from the surface due to the reducing action of CO. First, we have used molecular dynamics simulations and density functional theory calculations to elucidate the mechanisms of removal of these surface species by CO, and show that this reduction process proceeds without degradation of the underlying graphene sheet; CO2 and H2O are the only surface reaction products. We also show that the corresponding activation energy barriers for these reactions are easily surmounted at low temperatures. Second, the removal of oxygen-containing functional groups from GO by CO is confirmed experimentally using in situ attenuated total reflection Fourier transform infrared spectroscopy, indicating the reduction of the GO surface with CO is consistent with our atomistic-level calculations. Third, through controlled generation of defects into an otherwise pristine graphene sheet, we show that exposure to CO results in near-complete healing of the sheet as demonstrated with ex situ Raman spectroscopy. Thus, our results indicate CO induced reduction of GO not only proceeds without damaging the underlying sheet, but also heals defects that are produced in the production of GO via exfoliation of oxidized graphite.