I fitted my impedance data at Randell circuit by Zview software but I don't know the whether the obtained impedance elements are accurate or should I change the fitting circuit?
Hi. Start by asking yourself if any extra element is justifiable based on what you know about your electrode. You can perfectly fit any experimental curve if you add enough elements, but it might not tell you anything about the real system. So, which quantities are you looking for? How is your electrode looking?
Impedance is quite a difficult technique, if you really know your electrode surface your can try to create your own models, but is not a easy task. Usually the Randles circuit fits very well a lot of different systems, to know if your data is well fitted you can just rely on the R^2 of your simulated spectrum. If your system is very well behaved you will probably do it in triplicate and observe a similar result for every component of your circuit.
Hi and thanks for your answers. I searched the articles to find best circuit for my system and found 3 circuits, but my eis data fits by all circuits and I don't which is my true circuit. Ofcourse the element data exteracting from the zview accompany with the high error percents, is it important?
Please remember what my late friend Prof. W. Lorenz said many years ago:
If you use enough fit parameters, you can fit an elephant.
This is a very good question, I also tried to figure out this issue in my research. I think the best model which fits your spectra must reflect the physical system under study. Every element in the model explains it physical impact in the actual electrochemical system (in your case). You can also get useful information about fitting approach for impedance spectra from the following article
"In situ electrochemical characterization of natural pyrite as a galvanic catalyst using single-particle microelectrode technique in ferric sulfate solution" by my honorable professor David G. Dixon
I hope this will provide enough guidance to understand the fitting approach.
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