High Performance Glucose/O₂Biofuel Cell: Effect of Utilizing Purified Laccase with Anthracene-Modified Multi-Walled Carbon Nanotubes

Abstract

Laccase, a blue multicopper oxidoreductase enzyme, is a robust enzyme that catalyzes the reduction of oxygen to water and has been shown previously to perform improved direct electron transfer in a biocathode when mixed with anthracene-modified multi-walled carbon nanotubes. Previous cathode construction used crude laccase enzyme isolated as a brown cell extract powder containing both active and inactive proteins. Purification of this enzyme, yielding a blue solution, resulted in greatly improved enzyme activity and removed insulating protein that competed for docking space in this cathodic system. Cyclic voltammetry of the purified biocathodes showed a background subtracted limiting current density of 1.84 (±0.05) mA/cm2 in a stationary air-saturated system. Galvanostatic and potentiostatic stability experiments show that the biocathode maintains up to 75% and 80% of the original voltage and current respectively over 24 hours of constant operation. Inclusion of the biocathode in a glucose/O2 biofuel cell using a mediated glucose oxidase (GOx) anode produced maximum current and power densities of 1.28 (±0.18) mA/cm2 and 281 (±50) μW/cm2 at 25°C and 1.80 (±0.06) mA/cm2 and 381 (±33) μW/cm2 at 37°C, respectively. Enzymatic efficiency of this glucose/O2 enzymatic fuel cell is among the highest reported for a glucose/O2 enzymatic fuel cell.