The Relation of Microstructure, Materials Properties and Impedance of SOFC Electrodes: A Case Study of Ni/GDC Anodes

Andreas Nenning, Cornelia Bischof, Jürgen Fleig, Martin Bram and Alexander K. Opitz
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Andreas Nenning: Institute of Chemical Technologies and Analytics, Research Group for Electrochemical Energy Conversion, TU Wien, 1010 Vienna, Austria
Cornelia Bischof: Christian Doppler Laboratory for Interfaces in Metal-supported Electrochemical Energy Converters, 1010 Vienna, Austria
Jürgen Fleig: Institute of Chemical Technologies and Analytics, Research Group for Electrochemical Energy Conversion, TU Wien, 1010 Vienna, Austria
Martin Bram: Christian Doppler Laboratory for Interfaces in Metal-supported Electrochemical Energy Converters, 1010 Vienna, Austria
Alexander K. Opitz: Institute of Chemical Technologies and Analytics, Research Group for Electrochemical Energy Conversion, TU Wien, 1010 Vienna, Austria

Energies, 2020, vol. 13, issue 4, 1-30

Abstract: Detailed insight into electrochemical reaction mechanisms and rate limiting steps is crucial for targeted optimization of solid oxide fuel cell (SOFC) electrodes, especially for new materials and processing techniques, such as Ni/Gd-doped ceria (GDC) cermet anodes in metal-supported cells. Here, we present a comprehensive model that describes the impedance of porous cermet electrodes according to a transmission line circuit. We exemplify the validity of the model on electrolyte-supported symmetrical model cells with two equal Ni/Ce 0.9 Gd 0.1 O 1.95-δ anodes. These anodes exhibit a remarkably low polarization resistance of less than 0.1 ?cm 2 at 750 °C and OCV, and metal-supported cells with equally prepared anodes achieve excellent power density of >2 W/cm 2 at 700 °C. With the transmission line impedance model, it is possible to separate and quantify the individual contributions to the polarization resistance, such as oxygen ion transport across the YSZ-GDC interface, ionic conductivity within the porous anode, oxygen exchange at the GDC surface and gas phase diffusion. Furthermore, we show that the fitted parameters consistently scale with variation of electrode geometry, temperature and atmosphere. Since the fitted parameters are representative for materials properties, we can also relate our results to model studies on the ion conductivity, oxygen stoichiometry and surface catalytic properties of Gd-doped ceria and obtain very good quantitative agreement. With this detailed insight into reaction mechanisms, we can explain the excellent performance of the anode as a combination of materials properties of GDC and the unusual microstructure that is a consequence of the reductive sintering procedure, which is required for anodes in metal-supported cells.

Keywords: impedance spectroscopy; porous electrodes; Adler-Lane-Steele model; transmission line (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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