Mixed oxide electrodes with nominal composition Ti/[Ru(0.3)Ti(0,6)Ce(0.1-x)]O-2[Nb2O5]((x)), (0 less than or equal to x less than or equal to 0.1) were prepared through a process of thermal decomposition (450 degreesC) of chloride precursor mixture solutions. Composition effects on the surface properties were investigated and the oxide electrodes were characterized in acid solution: ex. situ by XRD and in situ by open circuit potential measurements (E-oc), cyclic voltammetry (CV), the double-layer capacitance (CV and electrochemical impedance spectroscopy techniques) and roughness factor (CV). Except the E-oc, all parameters varied with the electrode composition. It was shown that the presence of CeO2 increases the electrochemical active area, but it makes the coating less stable when submitted to continuous potential cycles because of cathodic dissolution of this oxide. By adding Nb2O5 this instability can be lowered. The maximum activity (voltammetric charge) was observed with the [RU(0.3)Ti(0.6)Ce(0.07)]O-2[Nb2O5]((0.03)) composition. (C) 2003 Elsevier Science Ltd. All rights reserved.