Extrapolation to zero frequency with first time constant of ferri-ferrocyanide/Pt interface using Foster equivalent circuit and factorized modelling

Abstract

An estimation of low frequency parameters at the interface of a ferri-ferrocyanide solution on a Pt rotating disk electrode is presented. The determination of the total resistance and effective (low frequency) capacity is based on a Foster's model extrapolation using electrochemical impedance spectroscopy measurements. The feasibility of the proposed approach has been demonstrated at equilibrium conditions and under two polarization points. Results show a good agreement with the identified and experimental values particularly in the extra-low frequency domain. Results also demonstrate that using factorized expression (poles and zeros) of the impedance allow the stability of the identified parameters and the calculation of the first time-constant of the system. Consequently, Foster's models as equivalent to Voight-type equivalent circuit can be used for the zero frequency extrapolation and predict the response of the interface in time domain that it is certainly useful for practical electrochemical systems.