Demonstrating the Use of a Fungal Synthesized Quinone in a Redox Flow Battery

Aqueous organic redox flow batteries (AORFBs) have gained increased interest as a promising solution to store energy from sustainable energy sources. Inspired by naturally occurring bio-quinones, we here propose a new electrolyte based on the fungal compound phoenicin. Phoenicin was produced using the filamentous fungus Penicillium atrosanguineum at a concentration of 1.24 g L⁻¹ liquid medium and extracted using ethyl acetate to a purity exceeding 95 %. The fungus may provide a benefit of high scalability of the biosynthesis-based production of the electroactive substance. Here, we demonstrate the performance of biologically produced phoenicin as a negative electrolyte in an RFB against ferro/ferricyanide, as a proof of concept, giving an initial capacity of 11.75 Ah L⁻¹ and a capacity decay of 2.85 % day⁻¹. For a deeper investigation of the battery setup, in situ attenuated total reflection infrared (ATR-IR) spectra of the phoenicin electrolyte were recorded. Symmetric cell cycling was performed to study the stability of this bio-based active material.