Fabrication of porous graphene electrodes via CO₂ activation for the enhancement of capacitive deionization

Capacitive deionization (CDI) is a simple, cost-efficient and environmentally-friendly method for brackish water desalination. In order to improve the desalination performance, the inner structures of the porous electrodes should provide more space for ion storage and transportation. Therefore, we utilized an efficient method to synthesize porous graphene electrodes based on the technique of pressurized oxidation and CO₂ activation. The prepared electrodes were characterized electrochemically by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy, and the desalination performance between different samples was compared as well. These results showed that AGE-30 had the highest electrosorption capacity (6.26 mg/g) among all samples, and this was attributed to its high specific surface area (898 m²/g), high pore volume (1.223 cm³/g), high specific capacitance (56.21F/g), and smaller inner resistance. Thus, the CO₂ activation is confirmed to be a useful method for the enhancement of the graphene electrodes for CDI.