Solid oxide fuel cells (SOFCs) represent a promising technology for the sustainable production of electricity, whose electrochemical performance needs further improvement. Electrochemical impedance spectroscopy (EIS) allows the identification of the dynamic response of the different processes that contribute to the electrode resistance, but the interpretation of spectra is often a complex task. In this contribution, we adopt a physically-based model for the deconvolution of EIS spectra of composite anodes made of nickel and scandia-stabilized zirconia. The model takes into account the electrochemical reaction (Butler-Volmer-type kinetics) as well as the transport of gases (Stefan-Maxwell model) and charges across the electrode thickness. The microstructural parameters required by the model are obtained from the tomographic reconstruction of the samples. The model is fitted and validated in samples with different Ni volume fractions in a wide range of temperature and hydrogen contents as shown in the Figure. Model simulations indicate that the low-frequency feature of the spectra is mainly due to gas diffusion while the high-frequency arc is the contribution of the coupled ionic transport and electrochemical reaction. In addition, material-specific kinetic parameters are extracted and applied for the interpretation of EIS data obtained in nanostructured electrodes. The results of the study are used to identify the limiting factors of the anode and to guide the design of more efficient electrodes.

Physically-based interpretation of impedance spectra of solid oxide fuel cell anodes

Bertei A
Investigation
;
2015-01-01

Abstract

Solid oxide fuel cells (SOFCs) represent a promising technology for the sustainable production of electricity, whose electrochemical performance needs further improvement. Electrochemical impedance spectroscopy (EIS) allows the identification of the dynamic response of the different processes that contribute to the electrode resistance, but the interpretation of spectra is often a complex task. In this contribution, we adopt a physically-based model for the deconvolution of EIS spectra of composite anodes made of nickel and scandia-stabilized zirconia. The model takes into account the electrochemical reaction (Butler-Volmer-type kinetics) as well as the transport of gases (Stefan-Maxwell model) and charges across the electrode thickness. The microstructural parameters required by the model are obtained from the tomographic reconstruction of the samples. The model is fitted and validated in samples with different Ni volume fractions in a wide range of temperature and hydrogen contents as shown in the Figure. Model simulations indicate that the low-frequency feature of the spectra is mainly due to gas diffusion while the high-frequency arc is the contribution of the coupled ionic transport and electrochemical reaction. In addition, material-specific kinetic parameters are extracted and applied for the interpretation of EIS data obtained in nanostructured electrodes. The results of the study are used to identify the limiting factors of the anode and to guide the design of more efficient electrodes.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/885387
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