Sm _0.5Sr _0.5CoO _{3- δ}-infiltrated cathodes for solid oxide fuel cells with improved oxygen reduction activity and stability

Sm _0.5Sr _0.5CoO _3-δ (SSC)-impregnated cathodes are fabricated by the solution infiltration of metal nitrates. The effects of complexing agents on the phase structure and the effects of pore formers on the porosity of the scaffold are examined and optimized. The thermal expansion behavior, electrical conductivities and electrochemical performance of the cathodes are characterized and optimized. A pure perovskite phase is formed after heating at 800 °C by adding a relatively small quantity of glycine as the complexing agent. Polyvinyl butyral is selected as the pore former for the preparation of porous Sm _0.2Ce _0.8O _1.9 (SDC) scaffolds. The thermal expansion coefficient increases slightly from 12.74 × 10 ^-6 K ^-1 to 13.28 × 10 ^-6 K ^-1 after infiltrating 20 wt% SSC into the SDC scaffold. The infiltrated cathode with 20 wt% SSC + 80 wt% SDC shows the electrical conductivity of 15 S cm ^-1 at 700 °C. A well-connected SSC network is formed in the cathode after infiltrating 20 wt% SSC into the SDC scaffold. Cathode polarization resistance values as low as 0.05 Ω cm ², peak power density values as high as 936 mW cm ^-2 and stable performance throughout 325 h of operation at 700 °C suggest that the cathodes with the 20 wt% SSC-infiltrated SDC are suitable for practical application. However, for the SSC infiltrated into the 8 mol% yttria-stabilized zirconia scaffold, the interfacial reaction continues to occur during the stability test at 700 °C. SDC is preferred as a scaffold for the infiltration of SSC to ensure long-term operational stability.