On the Extraction of the Effective Capacitance from Constant Phase Element Parameters

Constant phase elements (CPE) are widely used in fitting of electrochemical impedance spectra instead of ideal capacitances. The present work begins with a discussion of two commonly used models for conversion of the CPE parameters to an effective capacitance, i.e. Hsu and Mansfeld's and Brug et al.'s; and then continues with presenting alternative geometric assumptions to derive some other formulae. Afterward, it provides a comparison between the results of the formulae together with comments on their applications. Through discussing the relation between the models, this work offers a better understanding of the mathematics of impedance exhibiting frequency dispersion.