I want to measure impedance between two bare gold electrodes in a PDMS micro-channel. The results (please see the figure) were scanned one after another with a time interval of few seconds. However, no matter what solution I use (PBS or KCl or other solution), the scanned impedance always decrease as shown in the figure. Does anyone know what is the reason? How I can get very stable results?
Hi Pengfei,
Next time, please provide an image in format like png or jpg. The TIF file is so very large and takes long time to download.
To your question:
Almost all electrochemical systems show a transient behavior from the time you close cell switch and put it under potential control. So,in order to reduce the transient behavior, you must perform the EIS AFTER this effect has passed. So, close the cell switch and go to the potential where you want to do your EIS. Wait for 5 min or so. Now do the EIS, You should now expect to see the same curve if you repeat the EIS multiple times.
Observe that in you system 5min waiting might not be enough. I would suggest making an EIS each 30second for 20min with the first one starting directly after the closing of the cell switch. By doing so, you can study how the EIS values evolve by time. You will see that after a certain time, the spectra will not change any more. That time would be you optimized waiting time.
Good luck!
Gustav
Hi Gustav,
Thanks so much for your reply. I will try what you suggest. But do you know what is the reason that transient behavior happens in electrochemical cells?
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