An Electrochemical Route to Quantitative Oxidation of Graphene Frameworks with Controllable C/O Ratios and Added Pseudocapacitances

We report an electrochemical oxidation route to tunable C/O ratios in the graphene framework, creating enhanced pseudocapacitance with increasing oxygen content. Controlled surface functionalities on graphene enable a high specific capacitance and negligible electric conductivity loss. A specific capacitance of up to 279 F g^?1 was achieved for the functionalized graphene at a discharge current of 1 A g^?1 in 1 M H₂SO₄ electrolyte; this capacitance remained as high as 152 F g^?1 at 100 A g^?1. These values are much higher than those of non‐oxidized graphene. These excellent performances of the functionalized graphene signify the importance of precise control of the surface chemistry of graphene‐based materials.