Ca-containing Ba_(0.95)Ca_(0.05)C_(0.4)MFe_(0.4)Zr_(0.1)Y_(0.1)O_(3-δ) cathode with high CO_2-poisoning tolerance for proton-conducting solid oxide fuel cells

摘要

CO2-poisoning effect on cathodes is an unnegligible problem for commercial application of solid oxide fuel cells (SOFCs). In order to enhance CO2 tolerance of cathodes, partial replacement of Ba by Ca in BaCo0.4Fe0.4Zr0.1Y0.1O3-delta (BCFZY) cathode is proposed in this study. The stability of Ba0.95Ca0.05Co0.4Fe0.4Zr0.1Y0.1O3-delta (BCaCFZY) and BCFZY in CO2 -containing atmosphere is investigated comparably. When tested in a symmetrical cell and exposed to air with 1% CO2 or 10% CO2, the electrochemical performance of BCFZY cathode shows obviously degradation and carbonate particles are formed on the cathode surface. Exhilaratingly, the polarization resistance of BCaCFZY cathode is more stable and the cathode surface remains clean. The durability test in proton-conducting single cells further proves that the fine stability of BCaCFZY cathode can be achieved in air with 1% CO2 atmosphere. In addition, thermodynamic analysis reveals the mechanism of Ca doping to improve stability. Ca dopant itself has a high CO2 resistance and the introduction of Ca element reduces Ba segregation on surface. Base on the experimental results above, the BCaCFZY cathode is a promising candidate for SOFC applications.