Degradation of cobalt-free Ba0.95La0.05FeO3-δ cathode against CO2–H2O and Ce0.9Gd0.1O2−δ modification

Under actual operating conditions, cathode materials of Solid Oxide Fuel Cell (SOFC) tend to react with CO2 and/or H2O in air, resulting in degraded performances and stabilities. Here, effects of CO2 and H2O on Ba0.95La0.05FeO3-δ (BLF) cathode are systematically discussed by X-ray diffraction patterns (XRD), electrochemical impedance spectra (EIS) and scanning electron microscope (SEM). The results show that BaCO3 can be formed at 400 °C in a simulated air atmosphere. The content of CO2 and H2O has a significant influence on the polarization resistance (RP) of BLF, the RP of BLF is 0.161 Ω·cm2 in fresh air and 0.649 Ω·cm2 in 3% CO2–5% H2O-92% Air at 700 °C, respectively. But such degradation is reversible by switching working gas into fresh air again. In addition, we propose two alternative ways to improve tolerance of BLF cathode against CO2 and H2O: surface coating Ce0.9Gd0.1O2-δ (GDC) nano-particles on BLF cathode via spray-drying method and mechanical mixing GDC with BLF cathode. Compared with mechanical mixing, surface coating method is more advantageous in lowering the Rp of BLF cathode, which keeps 0.160 Ω·cm2 with 3% CO2–5% H2O-92% Air at 700 °C for 24 h.