Dear Kenya Kandwal , you may start by reading this introduction to EIS: https://www.biologic.net/topics/what-is-eis/.
Also you can read the various references given in the article.
To broadly summarize, EIS allows you to model the electrochemical reaction occurring at the electrode interface under study. Depending on your device (battery, fuel cell, supercaps, catalysts...), the reaction kinetics will be controlled by different factors and will have different impedance expressions. Best regards, Nicolas.
I suggest https://www.gamry.com/application-notes/EIS/basics-of-electrochemical-impedance-spectroscopy/, and chapter 2 of this paper: https://www.mdpi.com/1422-0067/23/24/15922.
I offer you a emerging perspective. I will speak only to dielectric responses (i.e. those modeled using R, C, and the power law term n. Using classical Impedance Spectroscopy, the surface is held at a constant voltage while a small AC potential is applied. The current response is then measured as a function of stepping the AC signal over a broad range of frequency. The data is often reported in terms of the calculated impedance. Data is most often reported in a linear Nyquist plot Z' vs Z" or a Bode Plot log Z', Z", |Z| and Phase angle (Tan theta) verses log frequency. Many models are reported in the literature, however I argue that the instrument only measures current flow through different features of the dielectric film (positive phase angles). If there is only one path, then only a single response (feature) is observed (one semi-circle in the Nyquist plot or one peak in the tangent plot in the Bode plot). the resulting current is indicative of the current path. If there are multiple plots then the current will choose the path based on the complex impedance of the that path, which will change as a function of applied frequency. In terms of the modeling circuit, the behavior is most appropriately modeled as a parallel combination of series RCn legs. Parallel legs because each path is independent of another. Modeled in this way R is related to the ionic current to a particular feature, C is related to inverse thickness of the dielectric and n indicate the population distribution of many micro/nano features contributing to an overall response. The latter n term is a direct result of the fact that EIS is a macro technique (large ascribe area) that is extremely sensitive to micro/nano features. EIS is rather unique in this regard as compared to high magnification spectrographic technique that pick out only the micro/nano features themselves. This perspective, although true as verified by independent measurements or observations, is often clouded by lingering understandings of the technique based only on perspectives of earlier proponent of the technique. The latter is the reason for much confusion and disagreements between interpretation is the literature. In summary, when only positive phase angles are observed, the dielectric response is in terms of relative current flow (as a function of frequency) different features of the film that have dissimilar impedance responses. Thank you for your question. See references: G.A. McRae, M. A. Maguire. Electrochemical Impedance of Anodic Films on Zr-2.5Nb. Journal of The Electrochemical Society 149: B123-B129
G.A. McRae, M.A. Maguire, C.A. Jeffrey, D.A. Guzonas, C.A. Brown. A Comparison of Fractal Dimensions Determined from Atomic Force Microscopy and Impedance Spectroscopy of Anodic Oxides on Zr-2.5Nb. Applied Surface Science 19: 94-105 (2002).
Maguire, M.A. Using EIS/PEDRA to Describe Barrier Oxide Films on Irradiated Zirconium Alloys. MRS Online Proceedings Library 1645, 106 (2014). https://doi.org/10.1557/opl.2014.61
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