Graphene coated carbon felt as a high-performance electrode for all vanadium redox flow batteries

Abstract

Graphene deposited on the surface of a carbon felt (CF) using a solution coating method has been developed as a high-performance positive electrode for an all vanadium redox flow battery (VRB). A key to obtain excellent electrochemical activity towards the VO2+/VO2+ redox couple is to wrap the CF using the graphene with high specific surface area and superb conductivity. It is found that the dipping times of CF into the graphene/Nafion solution significantly affect its electrochemical activity. The cyclic voltammetry (CV) results indicate that with 5 dipping times, the graphene coated CF (G/CF) exhibits the highest peak current and lowest peak potential difference towards the VO2+/VO2+ redox couple. More importantly, the VRB assembled with our novel G/CF cathodic electrode shows a decreased polarization during charge/discharge process compared with the control VRB with the pristine CF. Consequently, both the voltage efficiency and energy efficiency of the VRB with G/CF electrode have increased compared to the one with pristine CF. Our work provides a simple solution coating process to fabricate graphene modified CF electrode for VRB with high performance and this simple method is believed to be promising in other electrocatalysts applications.