Targetting redox polymers as mediators for laccase oxygen reduction in a membrane-less biofuel cell

Electrodes modified with co-immobilized redox enzymes and redox polymers can be used to form membrane-less biofuel cells. In this communication, we report on our initial studies of a membrane-less biofuel cell concept using an osmium-based redox polymer for laccase-mediated reduction of oxygen coupled to glucose oxidase-mediated oxidation of glucose. We then present a thermodynamic examination of mediators of laccase oxygen reduction, and stemming from this, target two redox polymers of potential use, an osmium-based redox polymer (E⁰′+0.40 V vs. Ag/AgCl) and a ruthenium-based redox polymer (E⁰′+0.63 V vs. Ag/AgCl). The former shows promise for use in membrane-less biofuel cell cathodes, whilst the latter's redox potential is too high to be an effective mediator of oxygen reduction by the Trametes versicolor laccase used in this study.