Kinetics and Mechanism of the H2O2 Electroreduction on the Peroxidase-Promoted Electrodes

The regularities of the bioelectrocatalytic reduction of H₂O₂ in the presence of peroxidase (POD) or a POD–Nafion composite adsorbed on the surface of carbon black or isotropic pyrocarbon are considered. The effect of the surface coverage with the enzyme, the H₂O₂ concentration, and the H₂O₂ supply rate to the electrode on the system activity is studied. Specific activities of three electrode types (POD adsorbed on carbon black or pyrocarbon, and the composite deposited on pyrocarbon) are close to one another. A mechanism for the bioelectrocatalytic reduction of H₂O₂ in a wide potential range is proposed. At potentials near the steady-state value, the reaction rate is limited by the electrochemical kinetics. At high polarizations, the formation of a POD compound with H₂O₂ is the limiting stage.