Electrochemical impedance spectroscopy (EIS) is a widely used multidisciplinary technique for characterizing the behavior of complex electrochemical systems. What sets EIS apart is its ability to isolate and distinguish the influence of various physical and chemical phenomena at a given applied potential—something which is not possible with «traditional» electrochemical techniques. EIS is employed in the study of a range of complex systems including batteries, catalysis, and corrosion processes. In recent years, EIS has also become more popular for investigating semiconductor interfaces and the diffusion of ions across membranes.

This seven-part series introduces EIS and covers basic theory, experimental setups, common equivalent circuits used for fitting data, and tips for improving the quality of the measured data and fitting. This Application Note (Part 1) focuses on the basic principles of EIS measurements.