Sulfur poisoning behavior of La0.6Sr0.4Co0.2Fe0.8O3–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 SO2 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.

The oxide ion conductivity of LaNi0.6Fe0.4O3 was studied by oxygen isotope exchange measurement and SIMS at 673 ˜ 1073K in p(O2) = 0.4 ˜ 20 kPa.

The effect of low concentrations of SO 2 (0.01 ppm) in air on the degradation of a porous La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) electrode was investigated as a function of operating temperature. At 1073 K, most of the introduced SO 2 became trapped as SrSO 4 in the vicinity of the air inlet, and consequently the degradation of cathode performance was not observed. At 973 K and 923 K, the SO 2 reached directly the electrochemically active region. Thus, the formed SrSO 4 caused a gradual decrease in cathode performance. These results suggest that sulfur poisoning behavior at 0.01 ppm SO 2 is mainly governed by two processes, the chemical reactions in the vicinity of air inlet and the electrochemically enhanced reactions in the active region; the former is strongly enhanced by temperature, whereas the latter additionally by the applied overpotential. SEM-EDX analysis confirmed the sulfur distribution was correlated to the degradation in the electrode performance. The concentration of SrSO 4 found near the triple-phase boundaries corresponded to the case where both the polarization and the ohmic resistances increased. Typical values for the effective reaction length essentially correlated with the k* and D* values obtained using the transmission line model. Results are in order-ofmagnitude agreement with the features obtained using SEM-EDX.