Electrochemical impedance spectroscopy

Electrochemical impedance spectroscopy (EIS) is a powerful tool to investigate properties of materials and electrode reactions. This Primer provides a guide to the use of EIS and a comparison with other electrochemical techniques. The analysis of impedance data for reduction of ferricyanide in a KCl supporting electrolyte is used to demonstrate the error structure for impedance measurements, the use of measurement and process models, and the sensitivity of impedance to the evolution of electrode properties. This Primer provides guidelines for experimental design, discusses the relevance of accuracy contour plots to wiring and instrumentation selection, and emphasizes the importance of the Kramers–Kronig relations to data validation and analysis. Applications of EIS to battery performance, metal and alloy corrosion, and electrochemical biosensors are highlighted. Electrochemical impedance measurements depend on both the mechanism under investigation and extrinsic parameters, such as the electrode geometry. Experimental complications are discussed, including the influence of non-stationary behaviour at low frequencies and the need for reference electrodes. Finally, emerging trends in experimental and interpretation approaches are also described. This Primer on electrochemical impedance spectroscopy (EIS) provides an experimental design guide to measure impedance and how these data are analysed. The range of applications that require EIS, from measuring battery performance to electrochemical biosensors, is highlighted. Limitations of the method along with emerging trends in experimental optimizations and data interpretation are also described.