Bioelectrocatalysis-based dihydrogen/dioxygen fuel cell operating at physiological pH

A biochemical fuel cell was constructed using H-2 as fuel to produce H2O in the reaction with O-2 at neutral pH and ambient temperature. The cell uses carbon felt as an electrode material for both the anode and the cathode and an anion exchange membrane as a separator. The anodic oxidation of H-2 was accelerated by methyl viologen-mediated electrocatalysis with bacterial cells Desulfovibrio vulgaris (Hildenborough) as catalysts, and the cathodic reduction of O-2 was accelerated by 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate)-mediated electrocatalysis with bilirubin oxidase as a catalyst. The bioelectrocatalytic systems allowed the cell to operate at 1.0 V with current 0.9 mA at an electrode of size 1.5x1.5x0.1 cm(3). The cell voltage attained 1.17 V at open circuit, which is close to the standard electromotive force 1.23 V. The cell voltage-current behavior is interpretable by linear sweep voltammetry using the same electrode system. On this basis, the electrochemistry behind the performance of the biochemical fuel cell is discussed.