Electrochemical Impedance Spectroscopy
Electrochemical Impedance Spectroscopy (EIS) · Also known as: EIS, AC impedance, impedance measurement
Electrochemical Impedance Spectroscopy (EIS) is a powerful technique for characterizing electrochemical systems by applying a small AC voltage over a range of frequencies and measuring the resulting current response. Developed in the late 1960s, EIS reveals the frequency-dependent resistance and capacitance of interfaces, allowing researchers to separate charge transfer kinetics, diffusion, and ohmic losses. It is widely used in battery research, corrosion studies, fuel cells, and biosensors.
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When to use it
Use EIS to diagnose electrochemical systems in situ: batteries under charge/discharge, corrosion at different potentials, or biofouling on electrodes. It is ideal for separating overlapping electrochemical processes and for monitoring gradual changes (aging, degradation). Apply at steady state or quasi-equilibrium. Avoid under transient conditions or when nonlinear effects dominate.
Strengths & limitations
- Separates kinetic, transport, and ohmic contributions through frequency dependence
- Non-destructive; can monitor system changes in real time
- High sensitivity to interfacial phenomena and electrolyte properties
- Mechanistically interpretable through equivalent circuit models
- Complex data interpretation; requires fitting to equivalent circuits (non-unique solutions possible)
- High-frequency measurements are difficult (typically >1 MHz); inductance and parasitic capacitance interfere
- Assumes linear (small-signal) response; large AC amplitudes introduce errors
- Timeconsuming for full frequency sweep; fast measurements require automated systems
Frequently asked
What is a Nyquist plot and why is it useful?
A Nyquist plot shows Z'' (imaginary impedance) vs. Z' (real impedance). Semicircles represent time constants; their diameter reveals resistance, and their position on the real axis shows series resistance. This visual representation reveals processes and their timescales intuitively.
Why do I need an equivalent circuit model?
EIS measures overall impedance, not individual process properties. An equivalent circuit (e.g., Rs-Rct-Cdl) maps observed impedance to physical parameters (ohmic resistance, charge transfer resistance, double-layer capacitance). Fitting extracts these parameters.
How small must the AC signal amplitude be?
For linearity, AC amplitude should be 5-10 mV or less (especially near the equilibrium potential). Larger amplitudes introduce harmonic distortion and nonlinear effects, violating the linear impedance model.
Sources
- Barsoukov, E., & Macdonald, J. R. (2005). Impedance Spectroscopy: Theory, Experiment, and Applications (2nd ed.). John Wiley & Sons. ISBN: 978-0-471-64749-2
- Orazem, M. E., & Tribollet, B. (2008). Electrochemical Impedance Spectroscopy. John Wiley & Sons. ISBN: 978-0-470-04141-9
- Lasia, A. (2014). Electrochemical Impedance Spectroscopy and its Applications. Springer. ISBN: 978-1-4614-8932-0
How to cite this page
ScholarGate. (2026, June 3). Electrochemical Impedance Spectroscopy (EIS). ScholarGate. https://scholargate.app/en/applied-physics/electrochemical-impedance-spectroscopy
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