Suppressing H2O2 formation in the oxygen reduction reaction using Co-doped copper oxide electrodes

Abstract

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 Co-doped CuO_x (Cu[Co]O_x/Au) catalyst was found to exhibit high activity and selectivity for the complete reduction of oxygen to water. Cu-rich doped-Cu_0.8Co_0.2O_x/Au electrodes exhibited nearly 97.5% selectivity for water compared to either CuO_x/Au (80%) or CoO_x/Au (70%). Cu_0.8Co_0.2O_x/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 CuO_x resulted in the formation of under-coordinated Co centers within CuO_x 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 doped electrode also demonstrated a superior hydrogen peroxide reduction ability.