I‘m currently trying to find a fit for my data but I‘m struggling with finding the correct equivalent circuit. I‘m working with a two-electrode-system and my electrolyte is my analyte.
I can’t use the randels circuit and I wondered, why it describes just the electrolyte, the double layer and one electrode.
In my understanding, the circuit (in the case of a two-electrode-system) should consist of the resistor and capacitor from my working electrode, the resistor from my electrolyte and again a capacitor and resistor for my counter electrode.
I‘m quite new to the topic, so if someone has an answer or idea it would be very helpful!
Dear Shanice Comminey , generally, in a three-electrode configuration, with one working electrode, one reference electrode and one counter electrode, there is only one interface under study, that of the working electrode. In your case, in a two-electrode configuration, you are absolutely right, you must consider two interfaces. Are you using an electrochemical cell ? Do you have the possibility to have a third electrode ? Best regards, Nicolas
Nicolas Murer thank you for your answer. Yes, I‘m using an electrochemical cell and sadly no, I can‘t change the experimental setup.
We usually consider only one electrode (working electrode, WE) because it is referred to as the reference electrode, RE. Thus, all interfacial processes occurring are taking place at the WE. Therefore, the equivalent circuit we propose considers all the current pathways contributing to the WE vs. RE impedance.
In the case of a two-electrode cell, you must consider the equivalent circuit that describes the current pathways that contribute to the impedance between your anode and cathode.
Suppose in your system, the charge transfer is absent. In that case, your equivalent circuit representing the interconnection of anode and cathode immersed in an electrolyte should be a resistance in serial connection with a double-layer capacitance (probably CPE). In your proposal, two resistors and two capacitors are equivalents to only one resistor and one capacitance. This is in agreement with Kirchoff's laws.
If there is a charge transfer in your system, you must include an additional resistor describing the global charge transferred between the anode and the cathode.
Best regards!
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