Synthesis and electrochemical properties of Sr3Fe1.8Co0.2O7 as solid oxide fuel cell cathode

Solid oxide fuel cells (SOFCs) attracted much attention for high efficiency, fuel flexibility, lower air pollution, etc., although, the high temperature is the main shortcoming for commercialization. One of the main hurdles to achieve intermediate temperature SOFCs is the conductivity of cathode materials at lower temperatures. Therefore, in this study, the conductive Sr_3 Fe_1.8 Co_0.2 O_7 cathode material with the Ruddlesden−Popper crystal structure was successfully synthesized and the effect of sintering temperature was investigated. X-ray diffraction analysis results revealed that the powder was approximately pure. Moreover, the field emission scanning electron microscope (FESEM) micrographs showed that the particles are rod-shaped with an average particle size of 670 nm. To evaluate the sintering effect on the electrochemical behavior of the synthesized powder, a paste of powder was painted on both sides of the Gadolinium doped Ceria (CGO) electrolyte and sintered at 1000°C and 1100°C. The electrochemical impedance analysis on symmetrical half-cells revealed that the minimum polarization resistance for the sintered cathode at 1000°C and 1100°C was determined 1.1 Ω.〖cm〗^2 and 1.6 Ω.〖cm〗^2 at 800C, respectively. The high-temperature sintering could affect the interface between CGO and SFCO as it was observed in the FESEM micrograph, and decrease transport pathways for oxygen ions conduction in higher sintering temperatures. Besides, the electrical conductivity of the sample was determined by the four-point probe electrical conductivity method in the temperature range 200_800˚C at room atmosphere. The results show that the maximum electrical conductivity at 427°C is 76 S.〖cm〗^(-1).