Multi-Walled Carbon Nanotube-Based Glucose/O₂ Biofuel Cell with Glucose Oxidase and Laccase as Biocatalysts

This study describes a multi-walled carbon nanotube-based glucose/O₂ biofuel cell with glucose oxidase and laccase as the anodic and cathodic biocatalysts, respectively. Upon being functionalized with L-α-phosphatidylcholine, one kind of lipid, multi-walled carbon nanotubes can serve as a support for glucose oxidase to form a three-dimensional, conducting and uniform bioanode that possesses a good bioelectrocatalytic activity toward the oxidation of glucose biofuel with solution-phased ferrocene monocarboxylic acid as the mediator to shuttle the electron transfer between glucose oxidase and multi-walled carbon nanotubes. In a similar way, the lipid-functionalized multiwalled carbon nanotubes can also be used to support the cathodic biocatalyst, i.e., laccase, and, more remarkably, to facilitate the direct electron transfer of laccase. As a result, the prepared biocathode is very active toward the reduction of oxygen without using any electron-transfer mediators. The biofuel cell has a 0.45 V open circuit potential and 34 μA/cm² short circuit current density in phosphate buffer (pH 6.0) separated with Nafion-117 membrane with anodic compartment containing 15 mM glucose and 2 mM ferrocene monocarboxylic acid and with cathodic compartment being saturated with O₂ at room temperature. A maximum power density of 3.2 μW/cm² is obtained with ca. 0.2 V potential output.