Microengineered cathode interface studies Page: 3 of 8
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Microengineered Cathode Interface Studies
T. Kueper (email@example.com; 630-252-4540)
R. Doshi (firstname.lastname@example.org; 630-252-4787)
M. Krumpelt (email@example.com; .630-252-8520)
Argonne National Laboratory
9700 South Cass Avenue
Argonne, Illinois 60439
The overpotential at the cathode/electrolyte interface has been recognized as an
important limitation on the performance of solid oxide fuel cells (SOFCs). This project is an
effort to gain a scientific understanding of which interface features and conditions contribute to
cathode polarization in SOFCs.
The Westinghouse tubular SOFC program has identified the cathode overpotential as an
important limitation on SOFC performance. The source of this overpotential has been debated
extensively in the literature, and a number of reactions have been proposed to be rate-limiting [1,2].
The site of the proposed limiting reaction will determine which characteristics of the
cathode/electrolyte interface need to be improved.
It is generally agreed that the total length of the air/electrode/electrolyte triple interface
should be maximized, but that the cathode reaction is not necessarily limited to this triple
interface. Mixed conductivity in either the electrode or electrolyte near the interface could allow
reactions to take place on the surface of the mixed conducting material. In these cases, the
degree of mixed conductivity or the surface properties of either material could determine the
reaction rate. Thus, in addition to the geometry of the triple interface, properties of the materials
that may be rate limiting include the electronic conductivity of the electrolyte, the ionic
conductivity of the cathode, and the catalytic properties of the surfaces.
Significant electronic conductivity in the zirconia electrolyte could arise in several ways.
Cations from the cathode are expected to diffuse into zirconia to some extent during normal fuel
cell fabrication, possibly increasing the electronic conductivity. Dopants can also be introduced
intentionally at the electrolyte surface. While such intentional doping has improved cathode
performance, it is unclear whether this improvement is due to electronic conductivity or to some
other effect, such as chemical stabilization of the interface [3,4].
Cathode materials vary widely in their ionic conductivity, and when mixed-conducting
materials are used the performance is usually superior. It is thus likely that the cathode reaction
takes place on the electrode surface. However, good performance is also seen when strontium-
doped lanthanum manganite (LSM), normally a poor ionic conductor, is used. An important factor
may be the changes created in the oxygen content of the cathode material when current is flowing;
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Kueper, T.; Doshi, R. & Krumpelt, M. Microengineered cathode interface studies, article, October 1, 1996; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc683824/m1/3/: accessed April 21, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.