On the Reversibility of Sustainable Symmetric Aqueous Organic Redox Flow Batteries

Herein, the effect of electrode anodization on the enhancement of the reversibility and the electrochemical activity of the redox‐active molecule alizarin in both positive and negative electrodes is reported. Alizarin is a bifunctional plant‐based anthraquinone redox species that exhibits irreversibility at positive potential (versus Ag/AgCl). The results show that the anodization of carbon paper increases surface area and introduces functional groups, which in turn promotes reversibility at the positive potential. To demonstrate the applicability of our technique, the modified electrodes are used in a symmetric aqueous organic redox flow battery, showing a significant improvement in capacity retention and Coulombic efficiency compared to pristine carbon electrodes.