Hello,
I have an electrochemical cell consisiting of two chambers. These two chambers are separated by a membrane.
Now, I want to observe the flow of current across this membrane for different voltages. To do this I am using a Pt wire electrode as the working/working sense electrode and a calibrated Ag/AgCl wire electrode as the reference electrode.
The reference electrode is in the other chamber with respect to the working/working sense electrode. I am using a Gamry potentiostat.
Now, if I apply voltage then would I get the current flow across the membrane ?
Or do I need to also use a counter electrode ?
You will have to use a counter electrode (CE).
As the name says the reference electrode enables to measure the correct working electrode potential in reference to a known electrode potential. To achieve this the current passing through the reference electrode has to be several magnitudes lower than the one passing through the working electrode (WE). High currents passing through the reference electrode would change the reference electrode potential. Also the reference electrode (RE) should be placed as near as possible to your working electrode to minimizre errors in measuring the potential by the ohmic resistance of the electrolyte (iR drop). Therefore, the electrode setup should be WE/RE - membrane - CE.
In such a way, the presence of membrane will simply increase the resistance between WE/RE and CE (on top of solution restance) and potentiostat will increase the voltage applied between WE and CE to ensure it delivers the voltage you want between RE and WE. The current you will measure will correspond to a redox reaction on WE (if any). If the resistance imposed by the membrane is too high, the potentiostat may even reach a limit of the output voltage.
I think you'd better work out conductivity of your membrane in a given solution. For this you need to arrange apt conductivity cell with it.
Hello Dr. Punckt,
Thanks for your explanation. I am thinking of placing the WE and RE on one chamber and the CE and another RE on the second chamber. The distance between the RE and CE , as well as, RE and WE is 5 mm approximately. My CE/WE are 1 mm dia Pt wires. The RE are basically Ag wires having a coating of AgCl. The solution in the chamber is a 1 mM Ferro/Ferri redox couple in 1X PBS buffer.
The total solution , taking into account both of the chambers , is approximately 3 ml, i.e. , 1.5 ml for each chamber.
The membrane is situated in the junction of the two chambers. It is AAO (200 nm pore diameter) , coated with gold and having some organic molecules attached to the gold coating.
Now, I want to see the current flow across the membrane when a particular voltage is applied.
I have a GAMRY potentiostat and for that the 4 electrode set up has a Working Sense electrode lead. Hence, should I connect one of the RE to the Working Sense lead ?
Kindly answer.
http://www.gamry.com/application-notes/electrodes-cells/two-three-and-four-electrode-experiments/
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