Sulfur poisoning behavior of La0.6Sr0.4Co 0.2Fe0.8O3-δ (LSCF6428) cathode was investigated at T = 1073 K (800°C) under 0.1 ppm of SO2-air mixture gas; the amount of supplied SO2 was controlled by changing the flow rate. Two stages of the performance degradation were found: a rapid degradation at the early stage and a subsequent monotonic degradation. The elemental distributions of SrSO4 showed a strong correlation between the electrochemically active sites and SrSO4 reaction sites in the vicinity of the LSCF6428/10GDC interfaces. Considerations were made to attribute the first and the second stages of performance degradation to the SO 2 adsorption and the SrSO4 formation, respectively. The SO2 adsorption mechanism was discussed in terms of the high concentration of oxide ion vacancies in the electrochemically active region under the cathodic polarization condition.
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