Tailoring Sr₂CoNbO_6−δ–Sm_0.2Ce_0.8O_1.9 Composite Cathode to Enhance Oxygen Reduction Reaction and CO₂ Tolerance for the Application in Intermediate Temperature Solid Oxide Fuel Cells

Intermediate temperature (IT) solid oxide fuel cell (SOFC) development is hindered by slow oxygen reduction reaction (ORR) and poor CO 2 tolerance at the cathode electrode. Here, we present a successful synthesis of a composite cathode material consisting of double perovskite structure Sr 2 CoNbO 6−δ (SCNO) and fluorite structure Sm 0.2 Ce 0.8 O 2−δ (SDC), using one-pot synthesis method. Integrating SDC to form a composite SCNO–SDC substantially augments the number of active sites, resulting in high ORR activity and lower polarization resistance. Forming a tight, coherent interface structure between SCNO and SDC particles is advantageous in reducing the thermal expansion coefficient and significantly improving the oxygen ion transport by creating a 3D pathway through the self-assembled growth of SDC particles. At 700 °C, the SOFC (full cell) utilizing SCNO–SDC composite cathode exhibits a peak power density (PPD) of 0.786 W cm –2, surpassing the PPD of 0.602 W cm –2 attained by the SCNO alone. Furthermore, upon exposure to CO 2, SCNO–SDC demonstrated remarkable performance recovery and tolerance. This study offers insights into the cathode material functioning of IT-SOFCs with enhanced electrochemical performance and long-term stability.