Bioelectrocatalytic reduction of dioxygen to water at neutral pH using bilirubin oxidase as an enzyme and 2,2′-azinobis (3-ethylbenzothiazolin-6-sulfonate) as an electron transfer mediator

Electrochemical reduction of dioxygen to water proceeds very effectively at 0.4 V versus Ag ∣ AgCl in pH 7.0 solution at an ambient temperature through the 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonate) (ABTS2−)-mediated and bilirubin oxidase (BOD) [EC 1.3.3.5]-catalyzed reaction of dioxygen. Electrochemistry of the ABTS2− oxidation and the indirect catalytic reduction of dioxygen with ABTS2− and BOD have been studied in detail to elucidate fully the bioelectrocatalytic behavior. The bioelectrocatalytic system using a carbon felt electrode has been examined and discussed in view of the cathode reaction in a biofuel cell.