Ag Doping Modulating Cathode Acidic Sites to Enhance Chromium Resistance for Intermediate Temperature Solid Oxide Fuel Cells

Cr poisoning is an important factor restricting the practical application of solid oxide fuel cell (SOFC) cathodes. In particular, the alkaline earth-rich perovskite oxide cathodes are prone to cation segregation and impurity poisoning at high temperatures, which can significantly reduce the cathode performance. To improve the Cr resistance of the cathode, the acid site of SrCo0.9Ta0.1O3- δ (SCT) was regulated by Ag doping, whose conductivity, catalytic activity, surface morphology, and composition were then systematically investigated. The results show that Ag doping enhances the conductivity of the material, and the doped material exhibits higher oxygen surface exchange coefficient, which is conducive to improving its cathodic catalytic activity. At 700 ℃, polarization resistance (Rp) of Sr0.9Ag0.1Co0.9Ta0.1O3- δ (SACT10) cathode is 0.0176 Ω·cm 2, significantly lower than that of SCT cathode (0.0366 Ω·cm2). In addition, due to the Ag doping strategy, the average valence state of Co in SACT10 material increases, which further increases the relative acidity and improves the Cr resistance. After operating in Cr-containing atmosphere for 22 h, Rp of SACT10 cathode is 0.205 Ω·cm2, significantly lower than that of SCT cathode (0.964 Ω·cm2), and fewer inert secondary phases are observed on the surface of SACT10 cathode after testing. All above results confirm that Ag doping can effectively increase acid sites, improve activity and enhance Cr resistance. SACT10 obtained in this work is expected to be a promising medium temperature SOFC cathode material.