Optimisation of composite cathodes for intermediate temperature SOFC applications

The electrochemical properties of the interfaces between porous composites of La0.6Sr0.4Co0.2Fe0.8O3−δ/Ce0.9Gd0.1O2−δ cathodes and Ce0.9Gd0.1O2−δ electrolytes have been investigated at intermediate temperatures (500–700°C) using AC impedance spectroscopy. Results indicate that the electrochemical pr...

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Bibliographic Details
Published in:Solid state ionics 1999-11, Vol.126 (1-2), p.163-174
Main Authors: Dusastre, V., Kilner, J.A.
Format: Article
Language:English
Subjects:
Ambipolar transport
Applied sciences
Effective medium percolation theory
Energy
Energy. Thermal use of fuels
Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc
Exact sciences and technology
Fuel cells
Intermediate temperature solid oxide fuel cells
Mixed conducting oxide composite cathodes
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Summary:The electrochemical properties of the interfaces between porous composites of La0.6Sr0.4Co0.2Fe0.8O3−δ/Ce0.9Gd0.1O2−δ cathodes and Ce0.9Gd0.1O2−δ electrolytes have been investigated at intermediate temperatures (500–700°C) using AC impedance spectroscopy. Results indicate that the electrochemical properties of these composites are quite sensitive to the composition and the microstructure of the electrode. The optimum Ce0 9Gd0.1O2−δ addition (36% by volume) to La0.6Sr0.4Co0.2Fe0.8O3−δ resulted in four times lower area specific resistivity, which classify this composite as a promising material for solid oxide fuel cells based on Ce0 9Gd0.1O2−δ electrolytes. The observed high performance of the composite electrodes at this composition is consistent with the effective medium percolation theory which predicts the ambipolar transport behaviour of composite mixed ionic-electronic conductors as a function of the volume fraction of each of the randomly-distributed constituent phases. Quantitatively, a slight discrepancy between measurements and theory was observed. This is believed to be due to the fact that the overall performance of a porous electrode is not only determined by the mixed conducting transport properties in the solid phase of the electrode, but also by the inherent catalytic property of the triple phase boundary, and by the gas transport to, or away, from the triple phase boundary.
ISSN:0167-2738
1872-7689
DOI:10.1016/S0167-2738(99)00108-3