Mechanistic understanding of monosaccharide-air flow battery electrochemistry

Recently, an inexpensive monosaccharide-air flow battery configuration has been demonstrated to utilize a strong base and a mediator redox dye to harness electrical power from the partial oxidation of glucose. Here the mechanistic understanding of glucose oxidation in this unique glucose–air power source is further explored by acid–base titration experiments, 13C NMR, and comparison of results from chemically different redox mediators (indigo carmine vs. methyl viologen) and sugars (fructose vs. glucose) via studies using electrochemical techniques. Titration results indicate that gluconic acid is the main product of the cell reaction, as supported by evidence in the 13C NMR spectra. Using indigo carmine as the mediator dye and fructose as the energy source, an abiotic cell configuration generates a power density of 1.66 mW cm−2, which is greater than that produced from glucose under similar conditions (ca. 1.28 mW cm−2). A faster transition from fructose into the ene-diol intermediate than from glucose likely contributed to this difference in power density.

► A mechanistic study on the highest power producing abiotic monosaccharide-air flow batteries to date.
► A user-friendly mediator dye, indigo carmine, and its performance in the abiotic cell was reported for the first time.
► Reducing sugars partial oxidation pathway, reaction mechanism, and products identified.
► Origins of better kinetics of fructose versus glucose explained.