In the EIS measurement for planar Cu foil electrode and 0.1 M NaClO4 electrolyte of pH 7, a nonideal CPE element is used to describe the double layer capacitance response instead of a pure capacity. For a simple equivalent circuit of the Randle circuit( Ru-Rct||CPE), Ru is the solution resistance, and Rct is the charge transfer resistance. there are two different equations to extract the double-layer capacitance from the CPE parameters (Q and n) as below cited from the reference in the add-file.
1. For the normal distribution, Cdl= Q1/n Rct(1/n-1)
2. For the surface distribution, Cdl= Q1/n (RuRct/(Ru+Rct))(1/n-1)
My questions are:
1. For the surface distribution, it's hard to understand why the double-layer capacitance can be influenced by electrolyte resistance.
2. How to assess which scenario is more likely to be more consistent with the system we are working with?
Hope to get some inspiration from the community.
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