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Summary In this study, Ce/Cr redox flow battery system (RFB), which had redox pair in different oxidation states, was performed in aqueous acidic medium for the first time in the literature. At Ce/Cr RFB system, optimization of acid (H2SO4), and active ion (Cr(III) and Ce(III) ions) concentration were executed by using differential pulse voltammetry and electrochemical impedance spectroscopy methods. The mass transfer type for positive electrolyte was determined by using of cyclic voltammetric method. Both chemical stability and changes on surface morphology of pencil graphite electrode were analyzed with scanning electron microscope. Cyclic charge/discharge test was performed for this novel electrolyte composition. Cell potential and the highest discharge capacity values were also determined as 1.52 V and 21.2 mAh L−1, respectively, at 0.8 mA cm−2 charge current density and 0.2 mA cm−2 discharge current density. Obtained data in this work can open a new perspective for the using of the alternative redox couples for the redox flow batteries.