Enhancing Electrochemical Performance of Spinel Co 0.6 Ca 0.4 Fe ₂ O ₄ Cathodes in Solid Oxide Fuel Cells with a Core/Shell Structure via Pr 0.2 Ce 0.8 O ₂ Impregnation

Achieving high-performance solid oxide fuel cell (SOFC) cathodes requires balance of catalytic activity and operational stability. Spinel-structured cobalt ferrite (CoFe2O4, CFO) offers excellent chemical compatibility but exhibits sluggish oxygen reduction reaction (ORR) kinetics. In this work, Pr-doped ceria (Pr0.2Ce0.8O2, PCO) was infiltrated into a Ca-doped cobalt ferrite (Co0.6Ca0.4Fe2O4, CC4FO) scaffold to construct a core–shell PCO@CC4FO composite cathode. X-ray diffraction and transmission electron microscopy confirm the formation of a uniform core–shell structure without secondary phases at an impregnation level of 10 wt %. Electrochemical impedance spectroscopy shows that the optimized PCO@CC4FO cathode achieves the lowest polarization resistance (0.694 Ω·cm2 at 750 °C), a 35% reduction compared to pristine CC4FO, along with enhanced electrical conductivity (0.796 S·cm–1). SEM and XPS analyses further reveal that PCO infiltration extends the triple-phase boundary and increases the surface oxygen-vacancy concentration, as evidenced by an increased Oads/Olat ratio (0.618 vs 0.52). These results demonstrate that PCO impregnation significantly improves oxygen surface-exchange kinetics. Overall, the PCO@CC4FO core–shell oxides show strong potential as high-performance SOFC cathodes.