A simple route to prepare free-standing graphene thin film for high-performance flexible electrode materials

Abstract

A free-standing graphene thin film is prepared by a simple electrochemical method applying positive and negative pulse electric signal, followed by air drying and being peeled off from the electrodes. During the process, formation and reduction of graphene oxide film have been simultaneously achieved. The free-standing graphene thin film obtained is characterized by X-ray diffraction, X-ray photoelectron and electrochemistry. The results show that the electrical conductivity and reduction of free-standing graphene film are influenced by pulse characteristic duty ratio and time of reaction. Their capacitive behavior is investigated by cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy using the two-electrode symmetric capacitor test. The free-standing flexible graphene film prepared under duty ratio 60% for 3 h exhibits a specific capacitance of 157 F g⁻¹ and good cycling stability. In addition, energy density and power density can reach to 3.36 W h kg⁻¹ and 20.5 kW kg⁻¹, respectively, at a discharge of 100 A g⁻¹. This approach opens up the possibility of fabrication of high-performance flexible electrode materials.