Electrochemical Impedance Analysis in Proton Exchange Membrane Fuel Cells

Electrochemical impedance spectroscopy (EIS) has emerged as an indispensable diagnostic tool for proton exchange membrane fuel cells (PEMFCs), enabling in situ characterisation of the complex interplay between ion transport, charge transfer and mass‐transport phenomena. By applying a small alternating signal over a broad frequency range, EIS reveals distinct spectral features corresponding to ohmic resistances of the membrane, double‐layer capacitances at electrode interfaces and diffusion or kinetic limitations within catalyst layers and gas‐diffusion media. Interpretation of these spectra relies on physically informed equivalent circuit and transmission‐line models, which translate impedance responses into quantifiable parameters such as proton conductivity, oxygen diffusion coefficients and reaction rate constants. Recent advances have refined these models to account for non-ideal capacitive behaviour, inductive loops at low frequencies and spatial variations along flow channels. Such developments underpin enhanced device design and real-time performance monitoring, supporting global efforts to accelerate the deployment of PEMFCs in transport, stationary power and portable applications.

Research from Nature Portfolio

Recent studies have proposed a streamlined physical model for cathode catalyst layers operating in oxygen-free environments. By combining analytical solutions for single-pore impedance with De Levie’s formula and an explicit ionomer distribution, researchers distilled the complex catalyst layer response into just six physically meaningful parameters. This model reliably fits impedance spectra under varying humidity, quantifying double-layer capacitance and proton conductivity in contact with platinum electrocatalysts. A simple fitting script has been made available to facilitate rapid interpretation of operando data, thereby offering a robust framework for catalyst-layer optimisation.

Electrochemical Impedance Analysis in Proton Exchange Membrane Fuel Cells publication trend

The graph below shows the total number of articles in electrochemical impedance analysis in proton exchange membrane fuel cells across all publications each year (not limited to Nature Index journals).

Technical terms

Electrochemical impedance spectroscopy (EIS): A technique that applies an AC signal across a cell and measures the resulting impedance over a range of frequencies to probe resistive and capacitive processes.

Equivalent circuit model: An electrical network of resistors, capacitors and inductors used to represent electrochemical processes and fit EIS data.

Inductive loop: A feature in a Nyquist plot appearing at low frequencies, indicative of processes such as dynamic adsorption or reaction intermediates.

Distribution of relaxation times (DRT): A mathematical method that separates overlapping impedance contributions by mapping them into a continuous spectrum of characteristic time constants.

Transmission‐line model: A spatially distributed circuit representation that captures combined ionic conduction and mass transport within porous electrodes.

References

1. Polymer Electrolyte Fuel Cell Degradation Mechanisms and Their Diagnosis by Frequency Response Analysis Methods: A Review. Energies (2020).
2. Inductive Low‐Frequency Processes in PEMFC‐Impedance Spectra. Fuel Cells (2020).
3. Transmission Line Impedance Models Considering Oxygen Transport Limitations in Polymer Electrolyte Membrane Fuel Cells. Journal of The Electrochemical Society (2019).
4. A Comprehensive Physical Impedance Model of Polymer Electrolyte Fuel Cell Cathodes in Oxygen-free Atmosphere. Scientific Reports (2018).