Electrochemical Impedance Spectroscopy
Published Online: 12 OCT 2012
Copyright © 2003 by John Wiley & Sons, Inc. All rights reserved.
Characterization of Materials
How to Cite
Barsukov, Y. and Macdonald, J. R. 2012. Electrochemical Impedance Spectroscopy. Characterization of Materials. 1–17.
- Published Online: 12 OCT 2012
Electrochemical impedance spectroscopy allows access to the complete set of kinetic characteristics of electrochemical systems, such as rate constants, diffusion coefficients, and so on, in single variable-load experiment. It is restricted to characteristics that describe system behavior in linear range of electrical excitation, for example, when it can be approximated by linear differential equations. It can be contrasted with other methods where explicitly nonlinear properties are investigated, such as cyclic voltammetry (see Chapter Cyclic Voltammetry).
A common example of linear conditions is voltage excitation below 25 mV, where V(I) dependency can be approximated as linear. Some of the parameters remain constant over a wide range of conditions, and once found under linear conditions can also be applied to model much wider ranges. An example of such parameters would be ohmic resistance of electrolyte or thickness of passivating film on the electrode.
Although impedance spectroscopy is sharing the variable-load experimental method with many other linear excitation electrochemical techniques, its analysis method is distinct, where a time-domain signal and response are converted to the frequency domain and their relation is found in the form of complex impedance. Complex impedance values over a range of frequencies form an impedance spectrum. Further analysis strives to derive system parameters from the impedance spectrum, typically by developing a model function connecting the impedance spectrum with system parameters and optimizing parameters to obtain a best fit to the impedance spectrum.
This article covers the basics of the experimental implementation of this technique, as well as background and mathematical approaches for developing model functions for most common systems and analysis of the experimental data to obtain system parameters.