Electrochemical enhancement of carbon paper by indium modification for the positive side of vanadium redox flow battery

In this study, indium modified carbon paper electrode is investigated as the positive electrode for all-vanadium redox flow battery (VRFB). The electrochemical performanceis studied using cyclic voltammetry, electrochemical impedance spectroscopy and stability test toward V (IV)/V (V) redox reaction. The results show that the modified carbon paper exhibits excellent electrocatalytic activity and stability after repetitive 100-cycle test in an electrolyte containing 0.5 M VOSO₄, while degradation is observed in pristine carbon paper. Such improvement is due to the indium particles deposited on the carbon fibers acting as stable active sites promoting the vanadium redox reactions and reducing charge transfer resistance as indicated by impedance measurement. Full cell performance is assessed via polarization curve analysis at different states of charge. A simple cell set-up (without flow field) employing the modified electrode exhibited limiting current of 125 mA cm², which is 73% higher than the cell employing pristine carbon paper (72 mA cm²) at SOC of 96%. Overall, the results demonstrate that indium deposition on carbon paper promotes the electrochemical performance and provides an opportunity for further investigation in the exploration of metal modification of carbon materials for VRFB.