Sonovoltammetry of oxygen at Cu-Ni alloy electrodes: Activation of alloy electrodes and sono-ring-disk voltammetry

The electrochemical reduction of dioxygen at cupronickel (Cu-30Ni) alloy electrodes is studied in alkaline 1.0 M KOH aqueous solution in the presence of intense ultrasound and compared to the case of the reduction of oxygen at platinum. In the presence of ultrasound an overall four-electron reduction process is detected at a freshly polished Cu-30Ni alloy electrode but the response is shown to diminish after scanning the potential positive. In contrast to the case of pure copper or pure nickel electrodes, prolonged treatment with ultrasound is shown to recover the original response. Sono-ring-disk voltammetry is used for the detection of products generated electrochemically- at the alloy disk electrode in the presence of ultrasound. Under an atmosphere of argon the oxidation of the surface of the Cu-30Ni alloy electrode is shown to be associated with a leaching process such as the loss of cuprite, Cu(OH)₄^2-. In the presence of oxygen the formation of hydrogen peroxide anions, HO^-₂, is demonstrated to remain only a minor reaction pathway (<15%) at Cu-30Ni alloy- and platinum electrodes for the case of the very high rates of mass transport induced by ultrasound. Atomic force microscopy images of electrode surfaces have been obtained to corroborate electrochemical results.