Advanced Electrochemical Performance and CO2 Tolerance of Bi0.5Sr0.5Fe1–xTixO3−δ Perovskite Materials as Oxygen Reduction Cathodes for Intermediate-Temperature Solid Oxide Fuel Cells

One key issue in the application of intermediate-temperature solid oxide fuel cells (SOFCs) is to develop novel cathode materials with excellent electrochemical performance and outstanding CO2 tolerance ability. In the present study, perovskite-type materials Bi0.5Sr0.5Fe1–xTixO3−δ (BSFTx, x = 0.05–0.20) are evaluated as possible Fe-based cathode candidates for SOFCs. The phase structure, thermal expansion property, and electrocatalytic properties of BSFTx cathodes are systematically studied. The best oxygen reduction reaction activity is observed in the Bi0.5Sr0.5Fe1–xTixO3−δ (BSFT0.15) cathode. The polarization resistance of the BSFT0.15 cathode is 0.085 Ω cm2 and the peak power density of the cell with the BSFT0.15 cathode reaches to 1.41 W cm–2 at 700 °C. Moreover, the BSFT0.15 cathode exhibits good CO2 tolerance and chemical stability in a high concentration of CO2. The excellent CO2 tolerance property is associated with remarkable acidity of the Ti4+ cation and the large average bonding energy of BSFT0.15.