Electrochemical Activation of Graphene at Low Temperature: The Synthesis of Three-Dimensional Nanoarchitectures for High Performance Supercapacitors and Capacitive Deionization

An electrochemical technique is developed to activate graphene oxide (GO) at relatively low temperature and assemble it into porous electrodes. The activation process is carried out in molten KOH by switching the polarity between 2 symmetrical GO electrodes. The electrochemically activated graphene (ECAG) showed a specific surface area as high as 2170 m² g^–1 and nanometer-sized pore created at a temperature as low as 450 °C. The ECAG electrode shows a significant enhancement in the electrochemical activity and thus improved electrochemical performance when being used as electrodes in supercapacitors and capacitive deionization (CDI) cells. A specific capacitance of 275 F g^–1 is obtained in 6 M KOH electrolyte, and 189 F g^–1 in 1 M NaCl electrolyte, which maintains 95% after 5000 cycles. The desalination capacity of the electrodes was evaluated by a batch mode electrosorption experiment. The ECAG electrode was able to remove 14.25 mg of salts per gram of the active materials and satisfy a high adsorption rate of 2.01 mg g^–1 min^–1. The low energy consumption of the CDI system is demonstrated by its high charge efficiency, which is estimated to be 0.83.