Membrane‐Less Biofuel Cell Based on Cellobiose Dehydrogenase (Anode)/Laccase (Cathode) WiredviaSpecific 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 O2to H2O at a formal potential higher than +500 mVversusAg/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 β‐lactose as a fuel and air/O2as an oxidising agent. The power output, the maximum current density and the electromotor force (Eemf) were found to be affected by the pH value, resulting in a maximum power output of 1.9 μW cm–2reached at pH 4.3, a maximum current density of about 13 μA cm–2at pH 3.5, and the highestEemfapproaching 600 mV at pH 4.0.