La-doped BaCoO₃ as a cathode for intermediate temperature solid oxide fuel cells using a LaGaO₃ base electrolyte

Cathodic behavior of BaCoO₃ doped with La was investigated in this study for an intermediate temperature solid oxide fuel cell (ITFC). Electrical conductivity of BaCoO₃ increased monotonically with an increasing amount of La doped for the Ba site at 1073 K p_o(2) = 10^-5 atm. Cathodic overpotential at 1073 K decreased with increasing La content and attained a minimum at X = 0.3-0.5 in Ba_1-xLa_xCoO₃. Since the cathodic overpotential of Ba_0.6La_0.4CoO₃ kept a small value at decreased temperature, Ba_0.6La_0.4CoO₃ is the optimum composition for the cathode of an ITFC among BaCoO₃-based oxides. When La_0.8Sr_0.2Ga_0.8Mg_0.15Co_0.05 O₃ was used for the electrolyte, the power density of the cell using Ba_0.6La_0.4CoO₃ for the cathode at 1073 K attained a value of 550 mW/cm², which is slightly higher than that using Sm_0.5Sr_0.5CoO₃ for the cathode. In addition, a low cathodic overpotential of Ba_0.6La_0.4CoO₃ was also maintained in air. ¹⁸O-¹⁶O exchange reaction was performed to estimate the surface activity for oxygen dissociation. It was found that BaCoO₃ exhibits high activity for the oxygen exchange reaction. Therefore, superior cathode property was assigned to the high surface activity of BaCoO₃.