A flexible graphene–carbon fiber composite electrode with high surface area-normalized capacitance

Abstract

We report a composite electrode material consisting of reduced graphene oxide (RGO) and carbon fibers (CFs) prepared by liquid-phase impregnation of cellulose paper in an RGO suspension, followed by freeze drying and activation. The composite electrode exhibited an excellent electrocapacitive performance in aqueous electrolytes. The electron-conductive carbon fibers derived from the carbonization of cellulose paper and the RGO nanosheets supported on the carbon fibers are favorable for charge storage and transport. Measured using a three-electrode system, the composite electrode delivered an area-normalized capacitance of 30 μF cm⁻² at a current density of 1 A g⁻¹ in a 6 M KOH electrolyte. A flexible solid-state electrochemical capacitor cell fabricated using the composite as both electrodes and polyvinyl alcohol–H₂SO₄ gel as the electrolyte delivered an areal capacitance of 49 mF cm⁻² at 2 mV s⁻¹. The effective surface area, the carbon nanostructure and the pores in such a composite all contribute to the high surface area-normalized capacitance.