A biomimetic redox flow battery based on flavin mononucleotide

TLDR

Redox flow batteries offer scalable, low‑cost energy storage, yet inexpensive organic electroactive electrolytes remain scarce; flavins, versatile biological redox molecules, present a promising but underexplored option. The study reports a flow battery powered by an aqueous electrolyte of sodium flavin mononucleotide. Nicotinamide is employed as a hydrotropic agent to increase the aqueous solubility of flavin mononucleotide. The FMN‑Na/ferrocyanide battery delivers over 99 % capacity retention across 100 cycles, likely because the oxidized and reduced FMN‑Na forms are resonance‑stabilized.

Abstract

Abstract The versatility in design of redox flow batteries makes them apt to efficiently store energy in large-scale applications at low cost. The discovery of inexpensive organic electroactive materials for use in aqueous flow battery electrolytes is highly attractive, but is thus far limited. Here we report on a flow battery using an aqueous electrolyte based on the sodium salt of flavin mononucleotide. Flavins are highly versatile electroactive molecules, which catalyse a multitude of redox reactions in biological systems. We use nicotinamide (vitamin B3) as a hydrotropic agent to enhance the water solubility of flavin mononucleotide. A redox flow battery using flavin mononucleotide negative and ferrocyanide positive electrolytes in strong base shows stable cycling performance, with over 99% capacity retention over the course of 100 cycles. We hypothesize that this is enabled due to the oxidized and reduced forms of FMN-Na being stabilized by resonance structures.