Synergistic effect study of EuBa0.98Co2O5+δ -Ce0.8Sm0.2O1.9 composite cathodes for intermediate-temperature solid oxide fuel cells

A novel Ba-deficient layered perovskite EuBa_0.98Co₂O_5+δ (EBCO) has been proposed as a high-performance cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Herein we report a systematic study on electrochemical properties of composite materials composed of EBCO and Ce_0.8Sm_0.2O_1.9 (EBCO-xSDC) with x ranging from 0 to 40 wt%. The results indicate that the EBCO-xSDC composite cathodes have excellent electro-catalytic oxygen reduction reaction (ORR) activity thanks to synergistic effects of high electronic conducting EBCO phase and ionic conducting SDC electrolyte. Among all these composite cathodes, EBCO-20SDC exhibits the best cathode performance, as evidenced by a low polarization resistance value of 0.028 Ω cm² at 700 °C in air. When tested in a complete fuel cell (Ni-YSZ|YSZ|CGO|EBCO-20SDC), a much higher maximum power density of 980 mW cm⁻² is achieved, compared with that of EBCO cathode-based fuel cell (505 mW cm⁻²). Furthermore, the rate-limiting steps toward oxygen reduction reaction at the EBCO-20SDC cathode interface are determined to explore the reaction kinetics and explain the enhanced electrochemical performance.