293 - Electrocatalysis of a cathodic oxygen reduction by laccase

The effect of laccase adsorbed on carbon-black electrodes on the electrochemical reduction of molecular O 2 has been studied. It is shown that laccase introduced into O 2 -saturated solution (acetate-phosphate buffer, pH = 5.5) shifts the potential towards the positive side and accelerates the O 2 electroreduction in the 1.2-0.6 V range. With the use of carbon-black adsorbed laccase, the potential reaches 1.2 V, which is close to the oxygen equilibrium potential. The dependence of the stationary potential on the pH and on the oxygen pressure indicates that the parameters ∂ U /∂pH and d U /d log p o2 correspond to the coefficients in the Nersnst equation for the O 2 -H 2 O couple. A scheme for the oxygen reduction with immobilized laccase is proposed on the basis of experimentally measured kinetic parameters.