Electrochemical performance of nanostructured La0.6Sr0.4CoO3−δ and Sm0.5Sr0.5CoO3−δ cathodes for IT-SOFCs

The electrochemical performance of nanostructured cathodes for IT-SOFCs based on perovskite-type mixed ionic/electronic conductors (MIECs) is investigated. Different compounds (La0.6Sr0.4CoO3−δ and Sm0.5Sr0.5CoO3−δ) and synthesis methods (freeze-drying and citrate complexation) were evaluated. These materials exhibited excellent performance (area-specific resistance values in the range of 0.05–0.20 Ω cm2 for an operating temperature of 700 °C), which improved with decreasing grain size. This performance can be attributed to the high specific surface area of these nanostructured cathodes, thus dramatically increasing the number of active sites for the oxygen reduction reaction. Under these conditions, the electrochemical properties are mainly controlled by oxide ion diffusion through the MIEC cathode, which becomes faster with decreasing grain size.

► Nanostructured cobaltites are proposed as high-performance IT-SOFC cathodes. ► Nanostructured cathodes exhibit ASR values in the range of 50–200 mΩ cm2 at 700 °C. ► The performance of nanostructured cathodes enhances with decreasing grain size. ► Ionic diffusivity of nanostructured cobaltites enhances with decreasing grain size. ► The cubic phase is retained at room temperature in nanostructured La0.6Sr0.4CoO3−δ.