A solid oxide fuel cell (SOFC) is a solid-state energy conversion system that converts chemical energy into electrical energy and heat at elevated temperatures. Its bipolar cells are electrochemical devices with an anode, electrolyte, and cathode that can be arranged in a planar or
tubular design with separated gas chambers for fuel and oxidant. Single chamber setups have bipolar cells with reaction selective electrodes and no separation between anode and cathode compartments. A nickel/yttria-stabilized-zirconia (YSZ) cermet is the most investigated and currently most
widespread anode material for the use with hydrogen as fuel. In recent years, however, doped ceria cermet anodes with nickel or copper and ceria as the ceramic phase have been introduced together with ceria as electrolyte material for the use with hydrocarbon fuels. The state-of-the-art electrolyte
material is YSZ of high ionic and nearly no electronic conductivity at temperatures between 800–1000°C. In order to reduce SOFC system costs, a reduction of operation temperatures to 600–800°C is desirable and electrolytes with higher ionic conductivities than YSZ are aimed
for such as bismuth oxide, lanthanum gallate or mixed conducting ceria and the use of thin electrolytes. Proton conducting perovskites are researched as alternatives to conventional oxygen conducting electrolyte materials. At the cathode, the reduction of molecular oxygen takes place predominantly
on the surface. Today's state-of-the-art cathodes are LaxSr1–xMnO3–δ for SOFC operating at high temperature i.e. 800–1000°C, or mixed conducting LaxSr1–xCoyFe1–yO3–δ
for intermediate temperature operation, i.e. 600-800°C. Among the variety of alternative materials, SmxSr1–xCoO3–δ and BaxSr1–xCoxFe1–xO3–δ are perovskites
that show very good oxygen reduction properties. This paper reviews the materials that are used in solid oxide fuel cells and their properties as well as novel materials that are potentially applied in the near future. The possible designs of single bipolar cells are also reviewed.
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Document Type: Research Article
Publication date: December 1, 2004
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International Journal for Chemistry and Official Membership Journal of the Swiss Chemical Society (SCS) and its Divisions
CHIMIA, a scientific journal for chemistry in the broadest sense, is published 10 times a year and covers the interests of a wide and diverse readership. Contributions from all fields of chemistry and related areas are considered for publication in the form of Review Articles and Notes. A characteristic feature of CHIMIA are the thematic issues, each devoted to an area of great current significance.
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