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

Abstract

normalCuxnormalCo3−xnormalO4 ( x=0 and 1) powders were prepared by a sol-gel method which favors high oxide specific surface areas with a larger value for normalCo3normalO4 , ascribed to a larger powder mesopore volume. X-ray diffraction measurements reveal that CunormalCo2normalO4 particles are less crystalline than normalCo3normalO4 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 normalCo3normalO4 contains Co2+ and Co3+ species at the surface, tetrahedral Co2+ cations being predominant. In the case of CunormalCo2normalO4 , Cu+ , Cu2+ , and possibly Cu3+ cations are also detected, octahedral Cu2+ showing the highest concentration among the copper species. Composite film electrodes, based on mechanically mixed normalCo3normalO4 or CunormalCo2normalO4 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 CunormalCo2normalO4 composite electrode containing the larger amount of oxide particles. Cyclic voltammetry experiments suggest that the surface normalCo2+∕normalCo3+ ratio is decreased when the electrodes are immersed into the KOH electrolyte, which may be associated to the formation of a superficial CoOOH layer.

Optical and mechanical characterization of novel cobalt-based metal oxide thin films synthesized using sol–gel dip-coating method

“…The sol-gel process is a soft chemistry method whereby the precursors are often in a form of colloidal solution that ultimately 'transforms' into an extensive network of either discrete or continuously-linked molecules. In our case, it was selected due to its inherently simple and safe characteristics in which solid-state synthesis could be accomplished at relatively low temperatures [17,25].…”

“…Likewise, there have been numerous studies conducted to characterize the physicochemical, magnetic, conductivity, electrochemical and thermal properties of copper-cobalt oxides [1,[17][18][19][20] as well as nickel-cobalt oxides [7,21,22].…”

Tailoring the physicochemical and mechanical properties of optical copper–cobalt oxide thin films through annealing treatment

“…Copper cobalt oxides are a family of metal oxides which have found important applications in electro-catalytic reactions and as thermoelectric material [1][2][3][4][5][6][7][8][9][10][11][12][13]. To enable improved designs for optimal performance in these applications, their physicochemical, electrochemical, magnetic, conductivity as well as thermal properties have been intensely studied, in conjunction with their structural characteristics [6,8,[13][14][15][16].…”

“…To enable improved designs for optimal performance in these applications, their physicochemical, electrochemical, magnetic, conductivity as well as thermal properties have been intensely studied, in conjunction with their structural characteristics [6,8,[13][14][15][16]. From these previous studies, it can be construed that temperature change in the synthesis process or application has substantial influence on their physicochemical properties.…”

“…The temperature independent diamagnetism reported for this type of copper cobalt oxide is in agreement with formal charge assignments of Cu + (d 10 ) and Co 3+ (d 6 , low spin) as suggested by Shannon et al [17] as well as from analysis of the electronic band structure determined by density functional theory (DFT) calculations [12,13]. The spinel-type of copper cobalt oxides tends to form a low crystallized single phase of copper cobalt oxide with a partially inverted spinel structure and minor segregations of new cobalt and/or copper oxide phases, which depend on the Cu/Co ratio in the precursor salt as well as the calcination temperature [8,18]. The increase of calcination temperature is typically accompanied by an increase in the degree of crystallinity of phases in copper cobalt oxides [16].…”