Suppressing H2O2 formation in oxygen reduction reaction using Co-Cu composite electrodes

Transition metal oxides form the basis of promising oxygen reduction electrocatalysts due to their low cost, high activity, and abundance on the planet. A new class of Cu[Co]Ox/Au catalyst was found to exhibit high activity and selectivity for the complete reduction of oxygen to water. The Cu-rich composite Cu0.8Co0.2Ox/Au electrodes exhibited nearly 97.5 % selectivity for water compared to either CuOx/Au (80 %) or CoOx/Au (70 %). Cu0.8Co0.2Ox/Au exhibited higher activity, stability, and better selectivity over a wide potential range when compared to well-known ORR catalysts such as Pt. In situ Raman spectroscopy revealed that the introduction of Co into CuOx resulted in the formation of under-coordinated Co centers within CuOx frameworks. These under-coordinated Co centers act as active sites for the scission of O-O bonds resulting in preferential formation of 4e reduction products. The composite electrode also demonstrated a superior hydrogen peroxide reduction ability.