Enhanced ORR Activity of A-Site-Deficient SrCo_0.8Nb_0.1Ti_0.1O_3−δ as a Bifunctional Air Electrode for Low-Temperature Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) working at intermediate and low temperatures (≤650 °C) demonstrate tremendous potential benefits including their ease of manipulation, improvement in durability, and utilization of metallic interconnects. However, the sluggish oxygen reduction reaction (ORR) of air electrodes at lower temperatures is the main reason for constraining their supply of power. In this work, an A-site-deficient perovskite Sr_0.95Co_0.8Nb_0.1Ti_0.1O_3−δ (S_0.95CNT) has been developed as a bifunctional air electrode for both oxygen-ion-conducting SOFCs (O-SOFCs) and proton-conducting SOFCs (H-SOFCs). The generation of 5% A-site deficiency in SrCo_0.8Nb_0.1Ti_0.1O_3−δ (S₁CNT) could increase the concentration of oxygen vacancies, thus facilitating the ORR kinetics for intermediate and low-temperature solid oxide fuel cells (ILT-SOFCs). The S_0.95CNT air electrode delivers excellent area specific resistances (ASRs) at 500 °C, with values of only 0.13 and 1.08 Ω cm² for S_0.95CNT on the Sm_0.2Ce_0.8O_1.9 (SDC) and BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3−δ (BZCYYb) electrolytes, respectively, and remarkable peak power densities (PPDs) at 600 °C for O-SOFCs and H-SOFCs of 1369 and 569 mW cm^-2, respectively, both about 18% higher than that of S₁CNT with no deficiency. Overall, this work supplies a simple and effective way to improve the ORR kinetics of S₁CNT as the bifunctional air electrode for ILT-SOFCs.