La-Doped BaCoO3 as a Cathode for Intermediate Temperature Solid Oxide Fuel Cells Using a LaGaO3 Base Electrolyte

Cathodic behavior of BaCoO 3 doped with La was investigated in this study for an intermediate temperature solid oxide fuel cell (ITFC). Electrical conductivity of BaCoO 3 increased monotonically with an increasing amount of La doped for the Ba site at 1073 K po 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-x La x CoO 3 . Since the cathodic overpotential of Ba 0.6 La 0.4 CoO 3 kept a small value at decreased temperature, Ba 0.6 La 0.4 CoO 3 is the optimum composition for the cathode of an ITFC among BaCoO 3 -based oxides When La 0.8 Sr 0.2 Ga 0.8 Mg 0.15 Co 0.05 O 3 was used for the electrolyte, the power density of the cell using Ba 0.6 La 0.4 CoO 3 for the cathode at 1073 K attained a value of 550 mW/cm 2 , which is slightly higher than that using Sm 0.5 Sr 0.5 CoO 3 for the cathode. In addition, a low cathodic overpotential of Ba 0.6 La 0.4 CoO 3 was also maintained in air. 18 O- 16 O exchange reaction was performed to estimate the surface activity for oxygen dissociation. It was found that BaCoO 3 exhibits high activity for the oxygen exchange reaction. Therefore, superior cathode property was assigned to the high surface activity of BaCoO 3 .