Roughened Graphite Felt Electrode with Enhanced Electrochemical Activity for Vanadium Redox Flow Batteries

A simple and effective method to roughen graphite felt (GF) by using manganese oxide as an etching agent has been developed for vanadium redox flow battery (VRFB) application. The specific surface area of roughened GF (R-GF) prepared at the optimized conditions reaches 8.49 m(2).g(-1), 7 times larger than that of the pristine one (P-GF), and more oxygen-containing functional groups are formed on the roughened surface. The experimental results show that the R-GF has higher peak current, smaller peak potential separation and lower charge transfer resistance than those of P-GF and GF treated with air oxidation (O-GF). The VRFB with R-GF electrodes exhibits a strongly enhanced electrochemical performance in terms of energy efficiency and utilization ratio of electrolyte at different current density. The large specific surface area with abundant oxygen-containing functional groups of R-GF has been shown to be extremely beneficial for improving the kinetics of the VRFB.