Boosting catalytic activities of carbon felt electrode towards redox reactions of vanadium ions by defect engineering

Vanadium redox flow batteries (VRFBs) are one of the most promising energy storage systems owing to their safety, efficiency, flexibility and scalability. However, the commercial viability of VRFBs is still hindered by the low electrochemical performance of the available carbon-based electrodes. Defect engineering is a powerful strategy to enhance the redox catalytic activity of carbon-based electrodes for VRFBs. In this paper, uniform carbon defects are introduced on the surfaces of carbon felt (CF) electrode by Ar plasma etching. Together with a higher specific surface area, the Ar plasma treated CF offers additional catalytic sites, allowing faster and more reversible oxidation/reduction reactions of vanadium ions. As a result, the VRFB using plasma treated electrode shows a power density of 1018.3 mW/cm 2 , an energy efficiency (EE) of 84.5%, and the EE remains stable over 1000 cycles.