ABSTRACT In order to address the limitations of the oxygen reduction reaction (ORR) activity of cobalt‐free Bi 0.5 Sr 0.5 FeO 3‐δ (BSFO) cathodes in intermediate‐temperature solid oxide fuel cells (IT‐SOFCs), a novel Bi 0.5 Sr 0.5 FeO 3‐δ ‐Sm 0.2 Ce 0.8 O 2‐δ (BSFO‐SDC) composite cathode was developed. XRD, TEM, and EDS confirmed that BSFO and SDC do not chemically react within the operating temperature range of IT‐SOFCs. Moreover, the hetero‐interfaces increase the active sites for the oxygen reduction reaction (ORR). The optimized BSFO‐20SDC (20 wt% SDC) exhibits a polarization resistance of 0.07 Ω·cm 2 at 750°C, 53% of pure BSFO (0.13 Ω·cm 2 ). First‐principles simulation based on density functional theory (DFT) reveals that the enhanced electrochemical performance is mainly attributed to the low oxygen vacancy formation energy of the BSFO‐SDC heterostructure (1.07 eV), which is significantly lower than that of BSFO (1.47 eV). The anode‐supported single cell (NiO‐SDC/SDC/BSFO‐20SDC) delivers a peak power density of 642 mW cm −2 at 750°C with humidified H 2 (∼3 vol% H 2 O) as fuel. Additionally, the composite has a thermal expansion coefficient (TEC) of 13.35×10 −6 K −1 matching SDC electrolyte, and the single cell maintains stable open‐circuit voltage (∼0.7 V) for 80 h at 750°C and 296 mA cm −2 . These results demonstrate that BSFO‐SDC is a promising cobalt‐free cathode for IT‐SOFCs.
Wang et al. (Fri,) studied this question.