KINETICS AND MECHANISM OF OXYGEN EVOLUTION ON IRO2-BASED ELECTRODES CONTAINING TI AND CE ACIDIC SOLUTIONS

A systematic investigation of the mechanistic features, the electrocatalytic activity, and the stability of thermally prepared ternary oxides of general formula Ir0.3Ti(0.7-x)CexO2 (0 less than or equal to x less than or equal to 0.7) has been carried out using O-2 evolution from 1.0 mol dm(-3) aqueous HClO4 as a model reaction. The surface state of the electrodes was monitored in situ by recording voltammetric curves before and after each experiment. Stability was tested by cycling the electrodes between 0.4 and 1.4V (the). For all compositions the anodic-to-cathodic charge ratio, q(a)/q(c), was close to one. Variation of the negative potential limit did not reveal the occurrence of the cathodic dissolution phenomena previously observed with a similar RuO2-based system. Tafel slopes were independent of the CeO2 content, with a value around 30 mV. The reaction order with respect to H+ was zero at constant overpotential and ionic strength. Some inhibition of the oxygen evolution reaction is observed as Ti is replaced by Ce.