Effect of Bi2O3 on the electrochemical performance of LaBaCo2O5+δ cathode for intermediate-temperature solid oxide fuel cells

The LaBaCo2O5+δ−x wt.% Bi2O3 (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% Bi2O3 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-20Bi2O3 was about 12.6 mV at 700 °C, while the corresponding value for LBCO was 51.0 mV. Compared to B2O3–Bi2O3–PbO frit, the addition of Bi2O3 significantly improved the long-term stability of cathode. Therefore, LBCO-20Bi2O3 can be a promising cathode for IT-SOFCs.