Fabrication and evaluation of Ag-impregnated BaCe0.8Sm0.2O2.9 composite cathodes for proton conducting solid oxide fuel cells

Ag–BaCe0.8Sm0.2O2.9 (BCS) composite cathodes are fabricated by an ion impregnation technique in this work, and the effect of fabrication details on their electro-performance is studied. The firing temperature of impregnated Ag has little effect on Ag loading but has a great impact on the polarization resistances. When fired at 400 °C, the minimum polarization resistance for symmetric cells reaches 0.11 Ω cm2 measured at 600 °C with an Ag loading of 0.40 mg cm−2. When fired at 600 °C, the minimum polarization resistance is 29.73 Ω cm2 at 600 °C with 0.24 mg cm−2 Ag-impregnated cathodes due to severe aggregation. The performance of Ag-impregnated cathodes is also compared with that of a Sm0.5Sr0.5CoO3−δ (SSC) impregnated cathode. With the same volume ratio of 57%, the polarization resistance of an Ag-impregnated cathode is only about half of that for a SSC-impregnated cathode. Resistance simulation suggests that the reduction of low frequency resistances is the main reason for the decrease in polarization resistances in Ag-impregnated cathodes, which is consistent with its high oxygen diffusion coefficient. With a 57 vol.% Ag-impregnated cathode fired at 400 °C, the maximum power density of single cells is 283 mW cm−2 at 600 °C, about 16% larger than that for a 57 vol.% SSC-impregnated cathode.