Effect of Bi₂O₃ on the electrochemical performance of LaBaCo₂O_5+δ cathode for intermediate-temperature solid oxide fuel cells

The LaBaCo₂O_5+δ-x wt.% Bi₂O ₃ (LBCO-xBi₂O₃, x=10, 20, 30, and 40) were prepared as composite cathodes for intermediate-temperature solid oxide fuel cells (IT-SOFCs) via the conventional mechanical mixing method. The effect of Bi₂O₃ on polarization resistance, overpotential, and long-term stability of the LBCO cathode was investigated. An effective sintering aid for LBCO cathode, Bi₂O₃ not only lowers its sintering temperature by ~200 C, but also improves the electrochemical performance within the intermediate temperature range of 600-800 C. Electrochemical impedance spectroscopy measurements showed that the addition of 20 wt% Bi ₂O₃ to LBCO exhibited the lowest area-specific resistance of 0.020 Ω cm² at 800 C in air, which was about a seventh of that of the LBCO cathode at the same condition. At a current density of 0.2 A cm^-2, the cathodic overpotential of LBCO-20Bi₂O ₃ was about 12.6 mV at 700 C, while the corresponding value for LBCO was 51.0 mV. Compared to B₂O₃-Bi₂O ₃-PbO frit, the addition of Bi₂O₃ significantly improved the long-term stability of cathode. Therefore, LBCO-20Bi ₂O₃ can be a promising cathode for IT-SOFCs.