The impact of post-synthesis processing in reduced graphene oxide materials for supercapacitor electrodes has been analyzed. A comparative study of vacuum, freeze and critical point drying was carried out for hydrothermally reduced graphene oxide demonstrating that the optimization of the specific surface area and preservation of the porous network are critical to maximize its supercapacitance performance. As described below, using a supercritical fluid as the drying medium, unprecedented values of the specific surface area (364 m2 g−1) and supercapacitance (441 F g−1) for this class of materials have been achieved.
The physical properties of carbon materials can be altered by doping. For instance, the electronic properties of graphene can be modulated by controlling the substitutional doping of the carbon lattice with N. In addition, C–N bonding configurations with three ring types are recognized: pyridinic-N, pyrrolic-N, and graphitic-N. Controlling the type and relative density of various types of substitutional N is an important objective that requires an extremely high level of precision when the atomic lattice is constructed. This control can be accomplished only via bottom-up methods, such as chemical vapor deposition (CVD). The number of reports on N-doped graphene (NDG) grown via CVD has increased over the past decade, but a reliable wafer-scale production strategy that can realize the desired atomic-precision growth of NDG is still lacking. To identify the most promising strategies and analyze the consistency of the results published in the literature, we review the CVD growth and characterization of two-dimensional NDG and two of the most popular applications of NDG films: field-effect transistors and energy storage devices.