Dear Tu Qing,

The high frequency tail is due to the capacitive behaviour of the electrolyte.

Please find below some introductory tutorials for EIS, maybe you will find them useful ?

https://www.biologic.net/documents/introduction-to-eis-electrochemical-impedance-spectroscopy-with-ec-lab-impedance/

https://www.biologic.net/documents/characterization-of-a-corroding-metal-impedance/

https://www.biologic.net/documents/study-of-the-insertion-reaction-by-impedance-impedance/

Best regards,

Nicolas

EIS data can be analyzed by ZsimpWin Software.

https://www.ameteksi.com/products/software/zsimpwin

Dear Tu Qing ,

First welcome to the field (EIS).

It depends (1, 2, ...) semi-circles, inductiveloops, lines, depressed graphs, time constants overlapping, distortion, distribution of time constants (Constant Phase Element, CPE) or PLM (Power Law Model as in the case of passive materials with thin oxide films).

1) The tail on the left should be investigated to know if it is the response of the perturbation of your system or it is just an artefact of measurent (usually due to the refereence electrode and a capacitor in parallel to the reference is added carfully) at high frequencies.

https://www.sciencedirect.com/science/article/abs/pii/S0013468611000090?via%3Dihub

2) It could be also due to the geometry-induced current and potential distribution

https://www.sciencedirect.com/science/article/abs/pii/S0013468616318989

3) Sometimes an ohmic drop is obtained (the complexe electrolyte resistance if I can say so).

https://www.sciencedirect.com/science/article/abs/pii/S0013468619314574

https://www.sciencedirect.com/science/article/abs/pii/S0013468622003498

4) To analyze your impedance diagrams I recommend you these two papers:

https://www.nature.com/articles/s43586-021-00039-w

Article Impedance Analysis of Electrochemical Systems

Hope it helps.

As far as my experience with Iviumstat , we need to plot Z' vs Z" than we click manually to get the amount. Thereafter it is substracted