PHYSICOCHEMICAL AND ELECTROCHEMICAL PROPERTIES OF CUCO2O4 ELECTRODES PREPARED BY THERMAL-DECOMPOSITION FOR OXYGEN EVOLUTION

Copper cobalt oxide with the spinel structure was investigated as an anode material for alkaline water electrolysis. This catalyst was prepared by thermal decomposition of nitrate precursors on titanium and nickel supports. Scanning electron microscopy analysis and electrochemical surface area measurements indicate that the electrodes are highly porous. Such preparation variables as the concentration of the mixed nitrates in isopropanol, the temperature of nitrate decomposition, the time of annealing, the catalyst loading, the nature of the substrate, the air flow during the thermal decomposition, and the cooling rate of the electrode have been investigated in detail to determine their influence on the morphology, the composition, the mechanical stability, and the electrocatalytic activity for oxygen evolution of the oxide films. It is shown that the performances can be ascribed to the variation in the roughness factor of the oxide layers. At 400-degrees-C, a resistive phase, presumably CuO, is formed and dispersed on the surface of Cu0.9Co2.1O4. This has a deleterious effect on the electrocatalytic activity. Copper cobalt oxide is oxidized and reduced prior to the oxygen evolution through a reaction which can involve the formation of the Co(IV)/Co(III) redox couple on the surface of cobaltite. The material prepared on nickel at 275-degrees-C for 1 h at a catalyst loading of 3.3 Mg CM-2 shows fairly low overvoltages for oxygen evolution.