Please refer to the photo attached. I am currently trying to determine my ion-exchange membrane (IEM)'s ionic conductivity with Potentiostatic electrochemical impedance spectroscopy (PEIS) with a 4-electrode configuration.
WE and CE are Pt wires, REs are Ag/AgCl electrodes placed close to the surface of IEM, and 0.5 M H2SO4 as the electrolyte.
I am using SP-300 Potentiostat (Biologic) with EC-Lab program to perform the PEIS:
Scan 1: 1MHz to 0.1Hz, with 10mV AC amplitude.
Scan 2: 3MHz to 0.1Hz, with 10mV AC amplitude.
Scan 3: 5MHz to 0.1Hz, with 10mV AC amplitude.
*3 scans were performed by using same IEM sample and electrolyte
May I know what caused the negative impedance value in high frequency region and what caused the spiral behaviour in the low frequency region?
Dear Hoang Thai Bao Ngo, is it possible to have a schematic description of your set-up as well as a picture (if possible) and the .mpr files of your measurements ? Also why do you expect a low-frequency Warburg behaviour in this case ? As I understand there is no electrochemical reaction at stake in your experiment as well as no electrode interface, you simply measure conudcitvity throughout the ion exchange membranes ? Thank you very much, Best regards, Nicolas
Nicolas Murer Dear Nicolas Murer, thank you for your suggestion. Please refer to the attached.
Honestly, this is my first time working with this measurement and I just learn by myself from literature. I applied 0 V vs. Ref but I'm not sure whether this should be "vs. Ref" or "vs. OCV". Does this setting highly affect my result?
After referring some literature, I tried to change my WE & CE from "Pt wire" to "Pt mesh" but my spectra (frequency range: 5MHz-0.1Hz) still starts from negative impedance value. May I know the reason for this behavior?
Thank you very much.
Best regards,
Bao Ngo.
Dear Hoang Thai Bao Ngo,
Your REs are new (and from the same quality) ?
Also, is it possible to perform (before EIS) a 4-electrodes CV[1-3] with this ('Cell setup.pptx') cell ?
1. CV, V-range: [-0.05, + 0.05] V.
2. CV, V-rate: 1 mV/s, or even less.
3. CV, N-cycles: 10, or more.
Dear Ioannis Samaras,
I ordered 2 REs at the same time and I have used them for 1-2 months.
Thank you for you suggestion, I will try it. May I know the purpose of that step?
Thank you very much.
Best regards,
Bao Ngo.
... the purpose is to check for some possible cell's electrolyte (and ... water) contaminants.
Dear Ioannis Samaras,
I have conducted the experiment as your suggestion.
My experimental procedure is as follows:
Please help me to check the results.
I suspect my REs (Ag/AgCl in sat. NaCl). I have another RE (SCE in sat. KCl) but not a pair of it so I cannot check that.
Thank you very much.
Best regards,
Bao Ngo.
Dear Hoang Thai Bao Ngo,
I encountered a similar situation with a cation-exchange membrane CEM while using the recommended configuration from the instrument's manual. Please find attached the configuration I used previously.
Regarding this instrument, it's important to note that there is an additional cable, the S3 (counter sense electrode CSE), which should be used as the second reference electrode. S1 (working sense electrode WSE) should be connected directly to the WE (cell electrode).
I hope that Mr. Nicolas Murer will provide further clarification on the right configuration.
Best regards,
Raouf
Dear Hammache Zine Ellabidine
Could you please describe in detail how you connect WE, CE, and REs with the cables, respectively?
Please see the attached. With my current configuration, I connect:
Is my connection correct? As your suggestion, should I switch S2 by S3 to connect with the second RE?
Best regards,
Bao Ngo
Hoang Thai Bao Ngo
You might try this connection mode mentionned in the manual of Biologic instruments,
P1 - WE
S1 (WSE) - (it's should be connected to the same working electrode than P1 (Cell electrode)).
S2- RE(1) in the WE side.
S3 (CSE)- RE(2) in the CE side.
P2- CE.
Best regards.
Dear Hoang Thai Bao Ngo
for the 4-electrode, 4-terminal connection:
P1 to WE
P2 to CE
S1 to WS
S2 on S3 to RE.
I hope this will work.
Best regards,
Nicolas
Dear Ioannis Samaras
Is there any special treatment for new electrodes?
Dear Hammache Zine Ellabidine ,
RE-'treatment' is the providers' authority, only.
However, I check by a Pot.-limited CV and the impedance of new (and RE) electrodes.
The impedance of a new-RE should be LOW (
Dear Hammache Zine Ellabidine and Nicolas Murer
Thank you for your suggestion. I will try to change my connection.
Best regards,
Bao Ngo
Hammache Zine Ellabidine Hoang Thai Bao Ngo in this article we give a procédure to check reference electrodes. https://www.biologic.net/topics/checking-and-validating-reference-electrodes/
I hope this helps,
Best regards,
Nicolas
Nicolas Murer Ioannis Samaras Thank you for this information.
I will check our REs using this method :-).
Best regards,
Raouf
at high frequencies, the impedance is negative because of the inductive phenomenon, whereas at low frequencies, the impedance response is parallel to the imaginary axis, due to the capacitive phenomenon. therefore, there is no difusional phenomenon (Warburg impedance).
Dear Naima Ghemmit-Doulache ,
the Zreal (part of the impedance) is negative; so, it is not an(y) inductive phenomenon; it is, simply, an exp. error, mainly, due to very high voltage (amplitude, 10 mV), for this case (heavy load, some mOhm).
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