Redox-active graphene dispersant and its ability to improve the conductivity and pseudo-capacitance of carbon film

Strong van der Waals force and π-π interaction make graphene difficult to be uniformly distributed in basic matrix for fabricating graphene-based composites. Employing dispersant is a major solution, however, current existing dispersants such as commercially available surfactants and polymer stabilizers scarcely provide ideal effect. Besides, they are always "useless" in final composites but difficult to remove. Therefore, endowing dispersant with specific property that matching the application of the final composite is essential.

Herein, a redox-active graphene dispersant (RAGD) is developed based on the grafting of p-phenylenediamine (PDA) with epoxy groups and further reacting with ethylamine. Homogeneous aqueous graphene dispersion is prepared by tip-sonication, and uniform graphene-based films are prepared via vacuum filtration method.

Graphene can be homogenously dispersed in water with concentration up to 15 mg mL^-1 in the presence of RAGD, and it can stably exist at room temperature for over six months. The π-π interaction of RAGD with graphene is tunable due to the PDA conjugated center is redox-active, and RAGD can be partially eliminated from graphene under alkali treatment. The electrical conductivity of the graphene film increases by about 34% after treated by 1 mol L^-1 NH₃·H₂O. Additionally, the graphene-based film including RAGD also shows much higher specific charge capacitance than those made with commonly used surfactants.