Effects of oxygen partial pressure on the performance stability of impregnated La0.6Sr0.4Co0.2Fe0.8O3 − δ–Sm0.2Ce0.8O2 cathodes of solid oxide fuel cells

• Performance degradation was related with surface chemistry for LSCF–SDC cathodes.
• Performance degradation was mainly caused by low frequency mass transfer process.
• Sr segregation on the surface was suppressed by lowering oxygen partial pressure.

The stability and surface composition of La0.6Sr0.4Co0.2Fe0.8O3 − δ (LSCF)–Sm0.2Ce0.8O2 (SDC) cathodes prepared by impregnation are investigated at 750 °C under open circuit and different oxygen partial pressures. The performance degradation during the test at Po2 = 0.21 atm is closely related to the low frequency mass transfer process. Little change of the electrochemical performance of cathodes is observed after 24 h test at Po2 = 0.001 atm. XPS patterns show that the decrease in oxygen partial pressure leads to the suppression of Sr enrichment on the surface of cathodes and retards the performance degradation.

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