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

Abstract

( and 1) powders were prepared by a sol-gel method which favors high oxide specific surface areas with a larger value for , ascribed to a larger powder mesopore volume. X-ray diffraction measurements reveal that particles are less crystalline than with crystallite size 10 times smaller. The sol-gel method allows formation of spinel oxide particles that do not contain any resistive CuO phase. X-ray photoelectron spectroscopy analyses have shown that contains and species at the surface, tetrahedral cations being predominant. In the case of , , , and possibly cations are also detected, octahedral showing the highest concentration among the copper species. Composite film electrodes, based on mechanically mixed or particles, carbon black Vulcan XC-72R, and poly(vinylidene fluoride-co-hexafluoropropylene), were formed on a glassy carbon disk surface. The highest intrinsic electrocatalytic activity for the oxygen evolution reaction is obtained for the composite electrode containing the larger amount of oxide particles. Cyclic voltammetry experiments suggest that the surface ratio is decreased when the electrodes are immersed into the KOH electrolyte, which may be associated to the formation of a superficial CoOOH layer.