Co-synthesis of Sm_0.5Sr_0.5CoO₃-Sm_0.2Ce_0.8O_1.9 composite cathode with enhanced electrochemical property for intermediate temperature SOFCs

A 70wt.% Sm_0.5Sr_0.5CoO₃ - 30 wt.% Sm_0.2Ce_0.8O₁₉ (SSC-SDC73) composite cathode was co-synthesized by a facile one-step sol-gel method, which showed lower polarization resistance and overpotential than those of physically mixed SSC-SDC73 cathode. The polarization resistance of co-synthesized SSC-SDC73 cathode at 800 °C was as low as 0.03 Wcm² in air. Scanning electron microscopy (SEM) images showed that the enhanced electrochemical property was mainly attributed to the smaller grains and good dispersion of SSC and SDC phases within the composite cathode, leading to an increase in three-phase boundary length. The dependence of polarization resistance with oxygen partial pressure indicated that the rate-limiting step for oxygen reduction reaction was the dissociation of molecular oxygen to atomic oxygen process. An anode supported fuel cell with a co-synthesized SSC-SDC73 cathode exhibited a peak power density of 924mWcm-² at 800 °C. Our results suggested that co-synthesized composite was a promising cathode for intermediate temperature solid oxide fuel cells (IT-SOFCs).