An oxidizable anion-excluding polymer-overlayer for oxygen electrodes

Here we describe an anion excluding ion-permeable membrane, which we evaluate on an O₂-electroreducing cathode poised at a strongly oxidizing potential, near the reversible potential of the O₂/H₂O half cell. The bioelectrocatalyst of the O₂ cathode consists of the cross-linked electrostatic adduct of a polycationic redox hydrogel and bilirubin oxidase (BOD), a polyanion at neutral at pH 7.3. If an uncured Nafion dispersion is applied on this bioelectrocatalyst, the polyanionic Nafion displaces the BOD in the electrostatic adduct, de-wiring the BOD. We show here that insertion of a polycationic poly(acrylamide-co-vinylimidazole) (PAA-PVI) between the bioelectrocatalyst and the Nafion prevents the dewiring of BOD. The resulting bi-layer membrane effectively excludes the urate, thiocyanate and NADH anions.