Abstract
Electrochemical Impedance Spectroscopy (EIS) has been known as a powerful tool for analyzing electrode reaction mechanism. In this review the history of EIS, the definition of electrochemical impedance, the general concept of transfer function, and the measurement method of electrochemical impedance using a transfer function analyzer are first introduced. Then, analytical methods of impedance spectra using electrical equivalent circuits and the kinetic theory of electrochemical reactions are stated. Finally, the future scope of EIS is briefly given.