Functionalized graphene as electrode material for capacitive deionization

Sulphonation of graphene sheets (GS) and their enhanced performance as electrode materials for capacitive deionization were discussed in this research. By altering the hydrophilicity of graphene through controlled introduction of sulphonic groups, the water contact angle of GS is much reduced, indicating a better wettability. Meanwhile, the sulphonated GS showed better dispersion and higher specific surface area, probably due to the negatively charged -SO^- 3 acting as a repellent on the surface to prevent serious aggregation. As a result, a salt removal efficiency of 83.4% and specific electrosorptive capacity of 8.6 mg/g, indicating an increase of 109% comparing with the unmodified graphene.