The effects of minor elements in La0.6Sr0.4Co0.2Fe0.8O3-δ cathodes on oxygen reduction reaction

• The effects of minor elements in SOFC cathodes are carefully investigated.
• Al and Si have negative effects on the surface exchange coefficient, ktr.
• The maximum ktr value was observed at around 100–1000 ppm for Ca and Ba.
• The enhancement of ktr was discussed in relation with surface Sr state.

It is known that the minor elements affect the performance of solid oxide fuel cell (SOFC). In this study, we focus on the influence of minor elements on the SOFC cathode properties. The Ca, Ba, Al, and Si, which originate from raw materials and production processes for SOFC cathodes, are investigated as minor elements that may have effect on the properties of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathode. To examine the effects of minor elements on the cathode properties, Ca, Ba, Al, and Si with a controlled concentration are added to the LSCF reference sample. Conductivity relaxation measurements are conducted to determine the chemical diffusion coefficient (Dchem) and surface exchange coefficient (ktr), which governs the overpotential characteristics of the LSCF cathode. The results show that Al and Si have negative effects on both Dchem and ktr while Ca and Ba do not alter Dchem and show weakly positive effects on ktr. The effects of Ca and Ba for the cathode properties are discussed on the basis of XPS measurements.