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Show 193 THE UNIVERSITY OF UTAH Biocatalysts are incorporated into traditional fuel cells to in order to harness energy from specific biochemical reactions. Incorporating biocatalysts into fuel cells increases the sustainability of this energy conversion device by removing the need for precious metals or expensive chemical fuels. Im-provements in the manner of incorporating biological catalysts onto the surface of electrodes leads to greater efficiency of fuel cells and greater power outputs. Laccase enzyme from Trametes versicolor is a copper-containing oxidoreductase enzyme responsible for the remediation of electrons in a metabolic pathway by catalyzing the reduction of molecular oxy-gen to water. We have employed it in this study, because it has a high turnover rate, is stable, and has been shown to do direct electron transfer. Hydroxylated multi-walled carbon nanotubes were synthetically modified with anthracene groups to improve the orientation of the laccase enzyme for catalytic direct electron transfer in the fabrica-tion of a biocathode. Initial characterization of this material with the laccase enzyme yielded back-ground subtracted current densities up to 140 μA/cm2. Initial use of this cathode in a biofuel cell with glucose-oxidase anode that uses a dimethylferrocene redox polymer as a mediator produced an open circuit potential of 0.819(±0.022) V, a maximum power density of 56.8(±1.8) μW/cm2 and a maximum current density of 205.7(±7.8) μA/cm2 (Figure 1). Further optimization of the cathodic system by purification of the laccase enzyme has resulted in greatly improved biocathodes capable of producing background subtracted current densities above 1.00 mA/cm2 on average in a stationary air-saturated system. Inclusion of this enzyme in a bio-fuel cell with the glucose oxidase dimethylferrocene anode produced an open circuit potential of 0.850(±0.050) V, a maximum power density of 260(±50) μW/cm2 and a maximum current density of 1.60(±0.60) mA/cm2 (Figure 2). Anthracene Modified Multi-walled Ca rbon Na notubes as Direct Electron Transfer Scaffolds for Enzyma tic Oxygen Reduction Michael Minson, Matthew T. Meredith, Shelley D. Minteer Department of Chemistry University of Utah Sustainability Michael Minson Matthew T. Meredith Figure 1: Characteristic cyclic voltam-mograms of laccase cathodes utiliz-ing crude laccase (red) and purified laccase (black) ran at 10 mV/s in 50 mM pH 4.0 citrate buffer. Figure 2: Representative polarization and power curves of a compartmentalized enzymatic biofuel cell consisting of the DET biocathode (in 150 mM citrate, pH 4.0) and a mediated glucose oxidase bioanode (100 mM phosphate, 200 mM NaCl, pH 8.4, 100mM glucose). Shelley D. Minteer |