Surface characterisation of IrO2/TiO2/CeO2 oxide electrodes and Faradaic impedance investigation of the oxygen evolution reaction from alkaline solution

Ti-supported electrodes of nominal composition Ti/Ir0.3Ti(0.7-x)CexO2 (0 less than or equal to x less than or equal to 0.7) were prepared by thermal decomposition of chloride precursor mixtures (T-cal = 450 degrees C; t(cal) = 1 h; O-2 flux = 5 L min(-1)). The effect of TiO2 substitution by CeO2 on the system surface parameters and oxygen evolution reaction was investigated by cyclic voltammetry and impedance measurements from 1.0 mol dm(-3) KOH. Independent of composition, the solid state redox couple Ir(III)/Ir(IV) dominates the surface properties of the anodes. Increasing the CeO2-content of the materials causes an increase in their active surface area, as supported by the anodic voltammetric charge, q(a), and double layer capacitance, C-dl, values. The small cathodic shift in E-p values observed as a consequence of CeO2 introduction into the material suggests an interaction among the components. R-Omega-values ranging between 1.3 and 2.9 Omega cm(2); independent of composition,are in;excellent agreement with the results of the Tafel investigation (similar to 2.0 Omega cm(2)), The R-ct-values reveal all CeO2-containing compositions have better overall activity than the reference cm composition (Ti/Ir0.3Ti0.7O2) Based on 1/R(ct)q(a) behaviour, however; best site activity was found for electrodes with low CeO2-content (10 and 20 mol%), (C) 1998 Elsevier Science Ltd. All rights reserved.