Effect of Non-Uniform Electrode Microstructure in Gas Diffusion Impedance

In this study, the impedance response of gas diffusion phenomena in anodes with non-uniform microstructure is simulated by solving the dusty-gas model in frequency domain. The microstructural parameters of the supporting and functional layers are evaluated from their tomographic reconstruction, as published in the literature. Simulations show that the gas diffusion dynamics is affected by the non-uniform microstructure, thus producing an additional feature in the Nyquist plot at high frequency. Such an additional feature may be erroneously attributed to other phenomena (e.g., charge transfer processes) when phenomenolo-gical equivalent circuits are superimposed to fit the data. The study shows that the gas diffusion fingerprint can substantially differ from the expected finite-length Warburg response in electrodes with non-uniform microstructure. The paper highlights the potential misinterpretations that can arise when interpreting impedance spectra with phenomenological models, especially when the coupling between microstructural characteristics and electrode dynamics is not properly taken into account.