A quinhydrone biofuel cell based on an enzyme-induced pH gradient

International audience; We report on an alternative concept of biofuelcell functioning based on the unconventional use of enzymes to create apH difference generating a potential difference between electrodes soaked in quinhydrone solutions. The electrode and quinhydrone solution were confined in a dialysis bag placed into a compartment containing either glucose oxidase and catalase for the biocathode or urease for the bioanode. In presence of 0.4 mol L−1 glucose and urea, the enzyme reactions generate apH difference of 3.55, both compartments being separated by an agar-agar wall. The resulting biofuelcell exhibits an open-circuit voltage and maximum power of 208 mV and 30.6 μW, respectively, without immobilization and electrical connection of the involved enzymes. In addition, this biofuelcell was able to provide continuously10 μA during 23 h, producing 0.133 J and 0.828 C. A similar biofuelcell configuration based only on dialysis bags was also developed. A graphite disk electrode elaborated by mechanical compression of graphite particles and quinhydrone, was placed in a dialysis bag itself confined into another dialysis bag containing enzyme solution. The resulting power and open-circuit voltage at saturating substrate conditions are 7.6 μW and 157 mV, respectively.