Membrane-Less Biofuel Cell Based on Cellobiose Dehydrogenase (Anode)/Laccase (Cathode) Wired via Specific Os-Redox Polymers

A membrane-free biofuel cell (BFC) is reported based on enzymes wired to graphite electrodes by means of Os-complex modified redox polymers. For the anode cellobiose dehydrogenase (CDH) is used as a biocatalyst whereas for the cathode a laccase was applied. This laccase is a high-potential laccase and hence able to reduce O-2 to H2O at a formal potential higher than +500 mV versus Ag/AgCl. In order to establish efficient electrochemical contact between the enzymes and graphite electrodes electrodeposition polymers containing Os-complex with specifically designed monomer compositions and formal potentials of the coordinatively bound Os-complex were synthesised and used to wire the enzymes to the electrodes. The newly designed CDH/Os-redox polymer anode was characterised at different pH values and optimised with respect to the nature of the polymer and the enzyme-to-polymer ratio. The resulting BFC was evaluated running on beta-lactose as a fuel and air/O-2 as an oxidising agent. The power output, the maximum current density and the electromotor force (E-emf) were found to be affected by the pH value, resulting in a maximum power output of 1.9 mu W cm(-2) reached at pH 4.3, a maximum current density of about 13 mu A cm(-2) at pH 3.5, and the highest E-emf approaching 600 mV at pH 4.0.