Analysis of Electrochemical Impedance Spectroscopy Data for Sputtered Iridium Oxide Electrodes

The measurement model program from Watson and Orazem was used to analyze electrochemical impedance spectroscopy (EIS) data for sputtered iridium oxide film (SIROF) micro-electrodes at potentials ranging from -0.4 to 0.6 V (Ag/AgCl). The frequency range used for the analysis was that determined to be consistent with the Kramers-Kronig relations. In addition, frequencies at which the ohmic impedance influenced the data were truncated. An interpretation model was developed that considered the impedance of the bare surface and the contribution of a porous component, based on the de Levie model of porous electrodes. The proposed model fit all 36 EIS spectra well. The effective capacitance of the SIROF system ranged from 17,000 μF/cm² at -0.4 V to a maximum of 30,000 μF/cm² at 0.2 and 0.4 V.