Interdigitated Array Electrode as an Alternative to the Rotated Ring−Disk Electrode for Determination of the Reaction Products of Dioxygen Reduction

Abstract

Electrochemical reduction of dioxygen in aqueous media can proceed to water, hydrogen peroxide, or a mixture of the two. The production of hydrogen peroxide, classically established with the rotated ring-disk electrode, can also be quantitatively assessed at interdigitated array (IDA) electrodes, where dioxygen is reduced at the set of microband generator electrodes and any H(2)O(2) produced is detected by its oxidation (back to O(2)) at the interdigitated set of microband collector electrodes. The sensitivity of the IDA for H(2)O(2) detection is higher owing to its more complete collection, and to the ensuing regeneration of O(2), which leads to an amplification of the generator currents. The production of H(2)O(2) is thus reflected both in the ratio of collector and generator electrode currents [the collection efficiency, coll(τ)] and in the ratio of the generator current with the collector potential on to that with it off [amplification factor, ampl(τ)]. The necessary theory for interpretation of the fraction ε of H(2)O(2) produced per dioxygen reduced is presented, based on conformal mapping techniques. Explicit equations are derived for ε at long times that are independent of the IDA dimensions and that can be used with any two-product electrochemical reaction analogous to the dioxygen reduction. Experimental data are presented for dioxygen reduction in acidic and basic media to illustrate application of the theory.