Mediated Biocatalytic Cathode for Direct Methanol Membrane-Electrode Assemblies

A membrane-electrode assembly (MEA) incorporating a biocatalytic cathode with a conventional, platinum-based anode is demonstrated in operation with hydrogen and methanol fuels. The biocatalytic cathode comprised the enzyme laccase and a redox mediator immobilized within a polymer hydrogel on a carbon-fiber paper support. The cell demonstrated an open circuit potential (OCP) of 1.1 V and a maximum current density of 6 mA/cm2 when supplied with hydrogen and an air-saturated citrate buffer solution at pH 4 and 40DGC. With 10 M methanol fuel, the OCP was 0.8 V and maximum current density was 4 mA/cm2. The tolerance of the laccase cathode to the presence of methanol was demonstrated by polarization of the MEA in the presence of methanol feed concentrations up to 10 M. A 6% increase in current density at 0.2 V cell potential was found for 10 M methanol as compared to 1 M methanol.