'In situ' and 'ex situ' characterization of the surface properties of the RuO2(x)+Co3O4(1-x) system

Ti-supported RuO2+ Co3O4 electrodes, prepared at 470 degrees C, were characterized by SEM, XRD, open-circuit potential (E-oc) and CV measurements. Binary mixtures has much higher areas compared with the pure oxides being the oxide morphology of mixtures with higher than 50 mol% RuO2, contents very similar to Ti/RuO2. XRD measurements of oxides showed intermediate compositions to be amorphous while those having close to pure compositions ale crystalline. E-oc,, data support that the surface electrochemistry of mixtures is controlled by the Ru-III/Ru-IV redox couple. In situ CV characterization, consistent with SEM and XRD results, showed the systematic substitution of Co3O4 by RuO2 to result in a significant increase in the current. In acid medium an intense cathodic current, attributed to CoO cathodic dissolution, is observed with Co3O4. Introduction of RuO2, however, stabilize the coatings. (C) 2000 Elsevier Science Ltd. All rights reserved.