Citrate–hydrothermal synthesis, structure and electrochemical performance of La0.6Sr0.4Co0.2Fe0.8O3−δ cathodes for IT-SOFCs

Abstract La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3− δ (LSCF) powders were synthesized by a combination of citrate and hydrothermal methods. The thermal decomposition behavior of the as-prepared powder was carried out by simultaneous thermogravimetry–differential thermal analysis. The calcined powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and particle size distribution (PSD). Screen-printed LSCF/CGO/LSCF symmetrical cells were sintered between 1150 and 1200 °C and studied by impedance spectroscopy in order to assess the cathode kinetics for the oxygen reduction reaction. Rietveld refinement of XRD data showed the formation of a single perovskite LSCF phase with crystallite size of 53 nm at 900 °C. The best area specific resistance (ASR) value, measured in static air, was found to be 0.34 Ω cm 2 at 750 °C, demonstrating that the novel citrate–hydrothermal method is an effective way to prepare cathode materials for SOFC. Cathode performance can be further enhanced by additional surface modification through impregnation with Pr-containing solution, reaching 0.17 Ω cm 2 at 750 °C. Furthermore, the activation energy of the PrO x -impregnated cathode is 83.4 kJ/mol, i.e., much lower than 123.8 kJ/mol, the best value determined for PrO x -free cathodes.