The equivalent circuit models (ECMs) used to electrochemical impedance spectroscopy (EIS) or ac impedance testing are commonly employed for determining fuel cell properties and diffusion behaviors in an electrochemical system are proposed. By applying a theoretical approach, the criterion for deciding the appropriate parameters of the extended model is presented. Then, given the transformation rules, the extended model is transformed into electrical equivalent circuits (EECs) by introducing the constant phase element (CPE) as the electrical element. Corresponding with the physicochemical phenomena of the system investigated, the modeling methodology can provide a suitable EEC for modeling the EIS and then give physical a understanding of the diffusion behavior of the system. Afterward, the practical applications of two different electrochemical systems are given to demonstrate the reliability of the extended model in the analysis of the diffusion, particularly during the actual operation. The results indicate the availability and the accuracy of the proposed extended model for modeling and interpreting the diffusion behaviors of an electrochemical system.
INTERNATIONAL JOURNAL OF INNOVATIVE COMPUTING INFORMATION AND CONTROL