Mechanism of hydrogen peroxide oxidation reaction at a glassy carbon electrode in alkaline solution

The voltammetric behavior of hydrogen peroxide at a glassy carbon electrode in alkaline solution was studied. An anodic prewave, preceding the well-kn own transport controlled oxidation reaction of hydrogen peroxide, was obser ved. The voltammetric current in this wave is independent of the rotation s peed of the glassy carbon disc electrode, even in what looks like a limitin g current plateau, denoted by a pseudo limiting current. This current is de pendent strongly on pH and temperature, does not vary linearly with hydroge n peroxide concentration and the reaction orders, with respect to hydrogen peroxide and hydroxyl ions (pH), are dependent on the hydrogen peroxide con centration. A mechanism that call explain these experimental results has be en proposed. It consists of two submechanisms, occurring simultaneously at the electrode surface, which are in competition with each other. Their rela tive predominance is controlled by the hydrogen peroxide concentration, whi ch can explain the varying reaction orders with respect to hydroxyl ions an d hydrogen peroxide. The current equation resulting from the proposed mecha nism shows the possibility of using the studied electrode reaction for the amperometric determination of hydrogen peroxide up to high concentrations. (C) 2000 Elsevier Science S.A. All rights reserved.