Introduction

Abstract

Among the various electrochemical techniques, electrochemical impedance spectroscopy (EIS) holds a special place. The classical electrochemical techniques present measurements of currents, electrical charges or electrode potentials as functions of time (which can also be related to the electrode potential). In contrast, EIS presents the signal as a function of frequency at a constant potential. This often poses some problems in understanding what is happening because electrochemists try to think in terms of time, not frequency. On the other hand, in optical spectroscopy, nobody thinks that light consists of the sinusoidal oscillations of electric and magnetic vectors of various frequencies, phases, and amplitudes. In spectroscopy, we used to think in terms of the frequency space (wave number, frequency, or some related functions as wavelength) and that what we observed was the Fourier transform of the optical signal.