New Ba_0.5Sr_0.5Co_0.8Fe_0.2O _3-δ + Co₃O₄ composite electrode for IT-SOFCs with improved electrical conductivity and catalytic activity

Ba_0.5Sr_0.5Co_0.8Fe_0.2O _3-δ (BSCF) + Co₃O₄ composites with different Co₃O₄ contents were synthesized, and their properties and performance as cathodes in IT-SOFCs were investigated. The diffraction patterns of the composites were well indexed based on the physical mixture of the BSCF phase and the Co₃O₄ phase. A surprising increase in the total conductivity of the composites was observed even though Co₃O₄ is a p-type semiconductor with a low conductivity. Electrochemical impedance spectra of symmetric cells indicated that both the area specific resistance and the activation energy were reduced in samples with Co₃O₄ contents of 5-20 wt.% with minimum values reaching 10 wt.%. A synergistic effect likely occurred between BSCF and Co₃O₄ that led to the better performance. An anode-supported single cell with 90 wt.% BSCF + 10 wt.% Co₃O ₄ delivered a promising peak power density of 1150 mW cm ^{- 2} at 600 °C.