Direct electron transfer catalyzed by bilirubin oxidase for air breathing gas-diffusion electrodes

A gas-diffusion electrode based on hydrophobized carbon black composite for enhanced enzymatic oxygen reduction is presented for the possible application as a biocathode in enzymatic fuel cells. Immobilized bilirubin oxidase (BOD) from Myrothecium verrucaria reduces oxygen in a 4-electron mechanism, as shown by Tafel kinetics and shows evidence of direct electron transfer. Under air-breathing conditions the galvanostatic polarization results in an open circuit potential of + 0.65 V (vs. Ag/AgCl, pH 7) and in + 0.5 Vat an applied current density of 0.35 mA cm(-2) which is 3 times higher compared to aqueous oxygen supply. (C) 2011 Elsevier BM. All rights reserved.