(226e) Fluorenone Based Anolyte for an Aqueous Organic Redox-Flow Battery

Here we present the first aqueous organic redox-flow battery based on a fluorenone anolyte. The use of polar carboxylic acid functional groups on the core fluorenone molecule enables good solubility under alkaline conditions. Three isomers of carboxyl functionalized fluorenone were screened, with the most promising, 9-fluorenone-2- carboxylic acid, achieving a maximum solubility of 0.8M in 1M KOH with a redox potential of -690 mV vs SHE. When paired with a ferro/ferricyanide redox couple, an open cell potential of 1.18 V was achieved. However, during charge/discharge cycling significant capacity loss was observed within the first few cycles. In addition, flow-battery tests showed low limiting current densities and peak power densities. Subsequent analysis revealed that the redox reversibility of the fluorenone molecules is strongly dependent on pH and potential, which can lead to undesired irreversible redox reactions.