Biofuel cell anode: NAD+/glucose dehydrogenase-coimmobilized ketjenblack electrode

Abstract We have studied the coimmobilization of glucose dehydrogenase (GDH) and its cofactor, oxidized nicotinamide adenine dinucleotide (NAD + ), on a ketjenblack (KB) electrode as a step toward a biofuel cell anode that works without mediators. A KB electrode was first treated with a sulfuric acid/nitric acid/water mixture to lower the overvoltage for NADH oxidation, and was next chemically modified with NAD + and GDH. The improved GDH/NAD + /KB electrode is found to oxidize glucose around 0 V vs. Ag/AgCl. A biofuel cell constructed with a bilirubin oxidase-immobilized KB cathode showed a maximum power density of 52 μW/cm 2 at 0.3 V.