Electrochemical Impedance Spectroscopy (EIS)
Electrochemical Impedance Spectroscopy (EIS) is an electrochemical techniques to measure the impedance of a system in dependence of the AC potentials frequency.
This is done by applying a sine-wave potential (AC potential) to the working electrode and read out the current, which should also be a sine wave. With the two sine waves (potential and current) the total impedance and phase shift for the corresponding frequency is calculated.
The data points are either displayed in a Bode plot or used to determine the real and imaginary part of the impedance and presented in a Nyquist plot.
By using equivalent circuit fitting the contribution of different effects to the impedance can be calculated. This allows to study changes of the interface in a very sensitive way. EIS is popular for coating research, label-free sensor research, or battery studies.