Electroreduction of oxygen on Fe3O4 electrodes. Part 2.—Rotating ring–disc electrode studies and mechanism
Abstract
A complete kinetic study of oxygen electroreduction on Fe3O4 electrodes is presented and the results are analysed with a general kinetic scheme that includes intermediate peroxide reduction (k3), heterogeneous disproportionation (k4), adsorption (k6) and desorption (k5). The kinetic analysis takes into account the chemistry of FeII at the oxide surface. The reduction of oxygen follows an electrochemical–chemical–electrochemical (ECE) mechanism with the chemical oxidation of surface FeII by O2 and the electrochemical reduction of the FeIII site. The kinetic similarities of the cathodic reduction of oxygen on other FeII systems, such as passive iron and iron-macrocycle-modified electrodes, are discussed.