Reducing the operating temperature of solid oxide fuel cells (SOFCs) to intermediate (650⁻850 °C) or even lower levels (400⁻650 °C) is an important practical requirement. However, the main obstacle to lowering the operating temperature is the poor oxygen reduction reaction (ORR) activity on the cathode side and, therefore, it is essential to explore cathode materials with good ORR activity in these temperature ranges. In this work, we investigated the possibility of using Sr₂Sc0.1Nb0.1Co1.5Fe0.3O6-2δ (SSNCF) as a suitable intermediate temperature cathode material. SSNCF thin films with different orientations were prepared using the pulsed laser deposition technique, and the relationship of the surface chemical states and ORR activity was discussed in terms of crystallographic orientation. The results showed that the SSNCF/YSZ grown along the [110] direction exhibited superior ORR activity compared to the SSNCF/SDC/YSZ thin film electrode grown along the [100] direction. This was explained by the variation in the Sr-surface enrichment and cobalt ion oxidation state using X-ray photoemission spectroscopy.
Keywords: ORR; SOFCs; mixed ionic electronic conductor; surface chemistry; thin films.