Modeling Dynamic Electrochemical Impedance Spectroscopy Using a Linearization Technique

This article investigates the modeling of dynamic electrochemical impedance spectroscopy. Using a linearization technique, three mathematical models are defined – dynamic, stationary, and filtered. The results show a closeness of the dynamic model to the experimental practice and significant effects of nonstationarity in the low-frequency region. The latter causes a failure in the fitting of the impedance spectra with classic equivalent circuits.

Herein, the physical modeling of dynamic electrochemical impedance spectroscopy using the example of a redox couple in solution is investigated. While the study of electrochemical systems during operation is of great interest, one is always confronted with challenges due to nonlinearities when exciting the system with both a cyclic voltammetry (CV) and a multisine. A two-component model is proposed, which first solves for the CV and then calculates the effect of the multisine by means of linearization around the CV of all the variables. Three models are tested: a dynamic transfer function model, a stationary transfer function model, and a quadrature band-pass filter model. The obtained impedance spectra are fitted using the regression analysis with Padé approximants and equivalent circuits. The results show that the dynamic transfer function model is very close to the experimental practice of obtaining dynamic impedance spectra through quadrature filters, and that stationarity has a significant effect on the impedance spectra in the low-frequency range.

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