La_0.6Ba_0.4CoO₃ as a cathode material for solid oxide fuel cells using a BaCeO₃ electrolyte

The cathodic reaction mechanism of a solid oxide fuel cell (SOFC) was investigated for an electrode-electrolyte system of La_0.6Ba_0.4CoO₃ (LBC)-BaCeO₃, under both the O^2- conducting and H⁺/O^2- mixed-ionic conducting conditions. AC impedance measurements were carried out, and the electrode interfacial conductivities were calculated. The experimental results revealed that the processes dominating the electrode resistance for the O^2- conducting and the H⁺/O^2- mixed-ionic conducting conditions are different. It was also found that the process dominating the electrode resistance changes at 700 °C under H⁺/O^2- mixed-ionic conducting conditions. The process dominating the electrode resistance above 700 °C is postulated to be the reaction O_LBC+H_LBC→OH_LBC. LBC showed high-performance cathode characteristics for a SOFC using BaCeO₃ electrolyte.