Ceramic-based anode materials for improved redox cycling of solid oxide fuel cells

  • Fu Q
  • Tietz F
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Abstract

In order to improve the reliability of anode-supported solid oxide fuel cells (SOFCs) in terms of tolerance to redox cycles, and to minimise fuel preprocessing for the direct use of readily available hydrocarbons in SOFCs, alternative ceramic-based anode substrate materials and functional anode materials were investigated, with the emphasis on perovskite oxides. Compared to (Sr/La)TiO3-δ and Nb2TiO7-δ, (Sr,Y)TiO3-δ ceramics (SYT, with a Y content of about 7 at.-%) reduced at high temperatures are promising redoxstable anode substrate materials due to their very small dimensional change upon redox cycling (0.14%). Correspondingly, the composite ceramic SYT/YSZ impregnated with -5 vol.-% Ni has a good chance of being applied as a redox-stable functional anode material due to its even smaller dimensional change upon redox cycling ( less than or equal 0.05%) and superior electrochemical performance for H2 oxidation (polarisation resistance [similar to] 0.2 Ωcm2 at 800°C). The small fraction of Ni homogeneously dispersed on the pore walls of the SYT/YSZ ceramic framework significantly enhances the electrocatalytic activity, and should not have a detrimental effect on the redox stability of the electrode. In addition, two mixed conductors with perovskite structure, (La0.8-Sr 0.2)0.94Al0.3Mn0.5O 3-δ and La0.4Sr0.6Ti0.4Mn 0.6O3-δ, were also investigated. They show promising electrochemical performance for the oxidation of H2. However, the high-level Mn substitution which seems necessary to achieve a significant electrical conductivity and catalytic activity has a detrimental effect on the chemical stability of these two materials. Consequently, they show relatively large and irreversible chemical expansion and are thus not considered to be qualified functional anode materials. © 2008 WILEY-VCH Verlag GmbH and Co. KGaA.

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Authors

  • Q.X. Fu

  • F. Tietz

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