Impedance Study of the Oxygen Evolution on the IrO2/TiO2/CeO2 System in Acidic Medium

The oxygen evolution reaction has been studied for various Ti supported Ir0,3Ti(0,7-x)CexO2 anodes by impedance measurements (EIS) at potentials between 0,4 and 1,6 V/rhe, in 1,0 mol dm-3 HclO4. The electrical parameters of the oxide electrode solution interface were obtained by fitting the experimental impedance data to theequivalent circuits, depending on the potential. The ohmic resistance values, situated between0,6 and 1,3, obtained from EIS are consistent with that obtained from the Tafel plots. The impedance spectrum in the cyclic voltammetry region (0,4-1,4 V) is an almost vertical line at the low frequency region, indicating the interfacial impedance is purely capactive. The (R1Q1) combination is related to the film processes observed in the high frequency domain of the impedance spectra, independent of the potential and composition. The Qdl describes the double layer capacitance, Cdl, of the oxide-solution interface, which is seen to increase significantly with CeO2 introduction, as a result of the electrode electrochemical active surface area increase. The introduction of CeO2 in the IrO2/TiO2 binary system results in a decrease of the Rct values with respect to the oxygen evolution reaction, which is probably related to the active surface area increase of CeO2-containing anodes.