Graphene nanosheets reduced by a multi-step process as high-performance electrode material for capacitive deionisation Original Research Article

We employed a novel three-step reduction of graphite oxide (GO) to obtain graphene nanosheets with high specific surface area and good dispersion in aqueous solution. Iron powder, as a mild and environmentally friendly reducing agent, was used at first in partial-reduction of GO and then, sulphonic functional groups (image) were introduced on the surface of partially reduced GO. The negatively charged image units can effectively prevent the graphitic sheets from aggregating and enhance specific surface area of graphene nanosheets after further reduction by hydrazine. The resulting graphene nanosheets exhibited a high specific surface area of 464 m2/g with mean pore size of 3.3 nm and specific capacitance of 149.8 F/g. Electrodes based on this kind of graphene nanosheets achieved a NaCl removal efficiency of 83.4% and specific electrosorptive capacity of 8.6 mg/g with outstanding regeneration capability, demonstrating great potential in application of graphene-based materials in capacitive deionization process for water desalination.