Frequency Response Analysis of a Nonstationary System: Electrochemical Transition of Polyaniline

Abstract

In this work, impedance spectra of polyaniline film electrode recorded at some redox transition potentials have been corrected for nonstationarity by application of Stoynov's 4-D method. The procedure consisted from: a) conventional measurements of a series of impedance spectra under strictly same experimental conditions, which are accompanied by monitoring of real operating time intervals for measurement of each particular impedance spectrum of the series, b) determination of functional dependence(s) between iso-frequency impedance values and operating time, and c) calculations of instantaneous IS for the time instant of the beginning of the first IS measurement. Comparison between measured and instantaneous impedance spectra, and also between their individual impedance parameter values pointed toward significant differences in charge transfer and transport resistance values. The results suggest that erroneous (either underestimated or overestimated) charge transfer and transport resistance values will be obtained if measured impedance spectra were not corrected for nonstationarity.