I am trying to do peak analysis on anodic biofilms in microbial fuel cells. To achieve this I am running CVs at different scan rates and then potentiostatic EIS. Because I noticed EIS behaviour varies with potential I am conducting EIS at different potentials set within the CV's potential window. The reasons for doing EIS are: to check uncompensated resistance is very small and to estimate capacitive currents.
Some sources state that a 'true capacitance' can be extracted from a Constant Phase Element by using this formula: C = (Q0*R)(1/n)/R. Is it then valid to use it for subtracting the capacitive contribution to current during a cyclic voltammetry according to Ic=C*(dV/dt)? I understand most models trying to explain the CPE are based on the distribution of some quantity over the surface of the electrode which in turn is the result of surface in homogeneities. Can someone tell me if this is a good approach, if the 'true capacitance' does not vary with scan rate and any other aspects I need to be consider?
For a theoretical approach have a look at
LSV/CV modelling of electrochemical reactions with interfacial CPE behaviour, using the generalised Mittag–Leffler function
C. Montella, J. Electroanal. Chem. 667 (2012) 68-47.
Hope this helps,
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