Glucose oxidase progressively lowers bilirubin oxidase bioelectrocatalytic cathode performance in single-compartment glucose/oxygen biological fuel cells

Enzymatic biological fuel cells (E-BFCs) were prepared using glucose oxidase (GOx) or FAD-dependent glucose dehydrogenase (FAD-GDH) as the anodic enzyme, coupled with direct electrocatalytic bilirubin oxidase (BOd) biocathodes obtained via incorporation of anthracene-modified multi-walled carbon nanotubes (Ac-MWCNTs). For GOx/BOd E-BFCs operating at pH 6.5 (200 mM glucose), open-circuit potentials, maximum current densities and maximum power densities of 0.47 ± 0.02 V, 332.7 ± 19.6 μA cm−2, and 46.5 ± 2.8 μW cm−2 were observed. For FAD-GDH/BOd E-BFCs operating in the same conditions, open-circuit potentials, maximum current densities and maximum power densities of 0.40 ± 0.01 V, 226.6 ± 8.0 μA cm−2, and 35.9 ± 1.3 μW cm−2 were observed. The effect of H2O2 (as produced by the enzymatic side-reaction of GOx) on BOd bioelectrocatalytic cathodes in E-BFCs was also investigated. Short-term testing (steady state) revealed that GOx did not produce significant quantities of H2O2 to affect BOd biocathodes. However, long-term testing (steady state, 24 hours) revealed that the quantity of H2O2 produced by GOx is large enough to have detrimental effects on the performance of the E-BFCs.