The Electro-Enzymatic Reduction of Dioxygen to Water Using Laccase and a Redox Mediator

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This project, supported as a Research Planning Grant in the Analytical and Surface Chemistry Program, is directed towards the development of a biofuel cell based on the enzymatic reduction of dioxygen to water. During the tenure of this 18- month standard grant, Professor G. Tayhas R. Palmore and her students at the University of California at Davis, will attempt to couple the redox enzyme laccase, which catalyzes the four electron reduction of dioxygen to water, to the carbon cathode of a fuel cell via use of chemical mediators, such as iron sulfate. The enzymatic facilitation of dioxygen reduction is accomplished near its formal potential, and should therefore result in a higher efficiency fuel cell than that possible using synthetic platinum metal catalysts. Professor Palmore has designed a prototype fuel cell which allows her to monitor the "turnover" of the enzyme and mediator using an in-line diode array spectrophotometer and the overall efficiency of the cell by measurement of the passage of charge across the cell using a coulometer. The success of this effort will culminate in a new family of low cost, high power, and environmentally safe fuel sources. A biological fuel cell is a device which converts chemical energy into electrical energy with minimal energy losses by the use of enzymatic catalysts. Typical fuel cells require the use of corrosive solvents and precious metals which can be costly to produce and/or dispose. In addition, the power output of a fuel cell is limited by the energy and rate at which electrons are shuttled through the various redox agents and across the anode and cathode compartments. With the use of a natural product, Professor Palmore has presented an elegant design for the generation of higher efficiency fuel cells that are " environmentally friendly".