Cu[sub x]Co[sub 3−x]O[sub 4] Used as Bifunctional Electrocatalyst

Composite film electrodes containing mechanically mixed or particles, carbon-black Vulcan XC-72R, and poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) were formed on the glassy carbon disk surface of a rotating ring-disk electrode (RRDE) and studied for the oxygen reduction reaction (ORR) in -saturated solution. The highest current densities were observed with and they increased with the oxide content in the film, hence clearly demonstrating the excellent intrinsic electrocatalytic activity of for this reaction. The results also showed that is a better electrocatalyst than with higher current densities and a greater number of electrons exchanged per molecule. It was found that the copper–cobalt spinel oxide component favors a total of in the oxygen reduction process. At the -based composite electrode, direct reduction of into ions (rate constant ) and the peroxide pathway (formation of ions and their reduction into ions, rate constants and ) are proceeding in parallel, with a ratio that increases with the overpotential when the oxide content is greater than 23.5%. At the -based composite electrode, is very weak with a ratio that decreases rapidly with the overpotential.