Identification of performance limiting electrode using asymmetric cell configuration in vanadium redox flow batteries

► Performance of a VRFB is investigated using asymmetric electrode configuration. ► Three different electrodes (i.e., raw, acid- and heat-treated) are investigated. ► Electrode functionalization is found to have different effects on (+) and (−) half-cells. ► Negative half-cell reactions are found to limit the overall performance of a VRFB. ► Poor performance of (−) half-cell is due to the undesired hydrogen evolution.