INTERDIGITATED ARRAY ELECTRODE AS AN ALTERNATIVE TO THE ROTATED RING-DISK ELECTRODE FOR DETERMINATION OF THE REACTION-PRODUCTS OF DIOXYGEN REDUCTION

Electrochemical reduction of dioxygen in aqueous media can proceed to water, hydrogen peroxide, or a mixture of the two, The production of h ydrogen peroxide, classically established with the rotated ring-disk e lectrode, can also be quantitatively assessed at interdigitated array (IDA) electrodes, where dioxygen is reduced at the set of microband ge nerator electrodes and any H2O2 produced is detected by its oxidation (back to 02) at the interdigitated set of microband collector electrod es, The sensitivity of the IDA for H2O2 detection is higher owing to i ts more complete collection, and to the ensuing regeneration of O-2, w hich leads to an amplification of the generator currents, The producti on of H2O2 is thus reflected both in the ratio of collector and genera tor electrode currents [the collection efficiency, coll(tau)] and in t he ratio of the generator current with the collector potential on to t hat with it off [amplification factor, ampl(tau)]. The necessary theor y for interpretation of the fraction epsilon of H2O2 produced per diox ygen reduced is presented, based on conformal mapping techniques. Expl icit equations are derived for epsilon at long times that are independ ent of the IDA dimensions and that can be used with any two-product el ectrochemical reaction analogous to the dioxygen reduction. Experiment al data are presented for dioxygen reduction in acidic and basic media to illustrate application of the theory.