Conductivity dependence of the polarization impedance spectra of platinum black electrodes in contact with aqueous NaCl electrolyte solutions

The polarization resistance and capacitance of platinum black electrodes in contact with aqueous NaCl solutions was investigated. A series of measurements were made at 25±0.1 °C in the 10 Hz to 10 MHz range using a HP 4192A Impedance Analyzer. The measurement cell has flat parallel platinum electrodes 15 mm in diameter, with a continuously variable spacing from 0.5 to 9 mm. They were platinized prior to each measurement. The electrolyte solution conductivities were in the 0.004–0.6 S m−1 range. The data were analyzed using an equivalent circuit consisting in a constant phase element in series with a parallel connection of a resistance and another constant phase element. The characteristic parameters of the model are presented as a function of the electrolyte solution conductivity.