Hello,
I am running EIS to determine the impedance spectra of my sensor. The sensor consists of gold electrodes deposited on a porous paper membrane. And the electrodes are modifying with a thiol molecule.
I am then taking an EIS measurement in a phosphate buffered solution (attached), and would like to fit this data to an equivalent circuit. I have tried a simple RS circuit, I have tried a Randle's circuit, but the data does not fit very well.
I did some digging and found a paper (linked) with a circuit that fits my data well; however, I'm not sure I can use it to describe the processes that are occurring in MY system. Any advice on how to better fit my data?
Thanks,
Hunter
http://www.sciencedirect.com/science/article/pii/S1567539409002059
Dear Stevenson,
You may try fitting your data with CPE (constant phase element) in place of C. It may result in better fit of your data.
For better fitting you may also try ZPLOT and ZSimpWin software. ZPLOT allows you to draw your own model/circuit and then you can fit your data, whereas in ZSimpWin, you have a set of equivalent circuits to which you can try fitting your data with.
Also, you can fit your data with many equivalent circuits and to find the most suitable circuit for your system, a better understanding of your system interface is required. Similar works in literature will help you in deciding the circuits components matching/mimicking your system for the equivalent circuit.
These links may be useful to you;
https://www.gamry.com/application-notes/EIS/basics-of-electrochemical-impedance-spectroscopy/
https://www.gamry.com/application-notes/EIS/equivalent-circuit-modeling-using-the-gamry-eis300-electrochemical-impedance-spectroscopy-software/
http://www.consultrsr.net/resources/eis/cpe1.htm
http://www.consultrsr.net/resources/eis/cpecalc.htm
Dear Hunter Stevenson,
the EIS data for your "sensor" are measured[1] using with two or more electrical contacts ?
Also, note, please, the parametric value of the VDC(= ?) polarization[2].
1. Good EIS data are critical and beyond advices "on how to better fit my data". An advice: remeasure the high frequency part of EIS.
2. Also, start at the VDC (=OCV value, for i=0) polarization. Add 2 more VDC parametric values, as overvoltages (about +-100mV).
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