Performance of a Glucose/O₂ Enzymatic Biofuel Cell Containing a Mediated Melanocarpus albomyces Laccase Cathode in a Physiological Buffer

We report on the performance of a prototype glucose/O₂ biofuel cell in a physiological buffer. The cell consists of cathode based on Melanocarpus albomyces laccase (with a reported T1 copper redox potential of + 0.26 V vs. Ag/AgCl) co-immobilised with an osmium redox polymer mediating film on glassy carbon (GC) separated by a Nafion 117 membrane from a GC anode in anolyte of glucose oxidase, N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) as a mediator, all immersed in pH 7.4 phosphate buffer solution containing 0.15 M NaCl and dissolved oxygen, thermostated at 37°C, mimicking physiological conditions. Two osmium redox polymers are employed for cathodic mediation: [Os(2,2′-bipyridine)₂(polyvinylimidazole) ₁₀Cl]^+/2+ (E°′ 0.22 V vs. Ag/AgCl) and [Os(4,4′-dichloro-2,2′-bipyridine)₂(polyvinylimidazole) ₁₀Cl]^+/2+ (E°′ 0.35 V vs. Ag/AgCl). Power outputs of 52 μWcm^-2 at 0.21 V and 17 μWcm^-2 at 0.34 V were obtained for assembled fuel cells containing the respective redox polymer-mediated laccase cathodes, illustrating the increased power obtained as a result of higher biocatalytic efficiency using a redox polymer with redox potential tailored for the enzyme.