Pyrolyzed graphene oxide/resorcinol-formaldehyde resin composites as high-performance supercapacitor electrodes

Abstract

A series of composites containing resorcinol-formaldehyde resin and graphene oxide was prepared by a sol–gel process. The composites were pyrolyzed in an inert atmosphere to form graphene sheet-containing activated carbon (AC) by using an excess amount of KOH as an activating agent. The chemical structure, physical properties, and morphology of the AC samples were characterized. Composites with the graphene sheet surrounded by thin layers of porous AC were obtained after pyrolysis. Pores with diameters ranging from one to hundreds of nanometres were observed from the AC samples and the pore size distribution and surface area were found to depend on the component ratio of the composites. The new AC samples were exploited as electrode materials for supercapacitors in both aqueous electrolyte and ionic liquid electrolyte. The electrochemical behavior was characterized by cyclic voltammetry, galvanostatic charge–discharge experiments, and electrochemical impedance spectroscopy. A high specific capacitance of up to 397 F g⁻¹ at a current density of 1 A g⁻¹ was achieved in KOH. In an ionic liquid electrolyte, the highest specific capacitance was calculated to be 287 F g⁻¹ at a current density of 0.5 A g⁻¹.