The critical role of bulk density of graphene oxide in tuning its defect concentration through microwave-driven annealing

Controlling the concentration of defects in reduced graphene oxide （rGO） to tailor its electrical and physicochemical properties has remained a significant challenge. We report that extent of microwave （MW）-driven annealing of rGO is influenced significantly by its bulk density, which allows us to vary its defect density and crystallite size over wide ranges by controlling this parameter. Extent of anneal- ing was investigated by multiple techniques including Raman and X-ray photoelectron spectroscopies, and electrical conductivity measurements. Improved corrosion resistance of rGOs upon annealing was ex- amined by cyclic voltammetry in H_2SO_4 electrolyte and temperature-programmed oxidation of rGO. Our results indicate that a low bulk density of rGO facilitates defect annealing, yielding high-quality carbon with 99.3 wt% purity, oxidative resistance as high as graphite powder, and an electrical conductivity of 36,000 S m-1 in the compressed powder form. These results demonstrate a prospective synthesis route for tailor-made nanocarbons from rGO through MW-driven annealing.