Diffusion-controlled oxygen reduction on multi-copper oxiclase-adsorbed carbon aerogel electrodes without mediator

Bioelectrocatalytic reduction of O(2) into water was archived at diffusion-controlled rate by using enzymes (laccase from Trametes sp. and bilirubin oxidase from Myrothecium verrucaria, which belong to the family of multi-copper oxidase) adsorbed on mesoporous carbon aerogel particle without a mediator. The current density was predominantly controlled by the diffusion of dissolved O(2) in rotating-disk electrode experiments, and reached a value as large as 10 mA cm(-2) at 1 atm O(2), 25 degrees C, and 8,000 rpm on the laccase-adsorbed electrode. The overpotential of the bioelectrocatalytic reduction of O(2) was 0.4-0.55 V smaller than that observed on a Pt disk electrode. Without any optimization, the laccase-adsorbed biocathode showed stable current intensity of the O(2) reduction in an air-saturated buffer at least for 10 days under continuous flow system.