Sr2Fe1·5Mo0·5O6-δ-based cathodes for solid oxide fuel cells: Microstructural considerations and composite formation with Pr-doped ceria

The mixed conducting Sr2Fe1·5Mo0·5O6-δ (SFM) is a promising cobalt-free oxygen electrode for solid oxide fuel cells (SOFCs). Therefore, we report on modifying the electrode microstructure of a single-phase SFM and the formation of a new composite electrode with ∼34 vol% of Ce0.8Pr0.2O2-δ (CPO, which also exhibits mixed conducting behavior). In our assessment, we tested the impact of repeated drying-screen-printing cycles on the deposition of the electrode films. Such a modification resulted in an optimal thickness within the 40–50 μm range while providing a higher solid fraction within the electrode-electrolyte region. This factor decreased the total polarization resistance for both electrode materials, as determined by electrochemical impedance spectroscopy. The results also indicated enhanced surface exchange kinetics with the addition of CPO, where the incorporation reaction is expected to occur at the SFM/CPO interface. Nevertheless, the overall performance of the composite electrode was hampered by an insufficient global electronic conductivity. As a result, the reduced effective electroactive area in the SFM/CPO composite electrode hindered the interfacial charge-transfer process. Our work provides an important investigation of both microstructural and compositional criteria for the future development of SOFC cathode design.