Improved electrochemical performance of SrCo_0.8Fe_0.2O_3-δ-La_0.45Ce_0.55O_2-δ composite cathodes for IT-SOFC

The performance of the SrCo_0.8Fe_0.2O_3-δ(SCF)-La_0.45Ce_0.55O_2-δ(LDC) composite cathodes was studied in this paper. The composite cathodes were prepared by screen-printing, and then sintered at 1200 °C for 2 h. Electrochemical impedance spectroscopy (EIS) and cathodic polarization test were carried out to investigate the electrochemical properties of the composite cathodes. The results showed that the composite cathodes had superior electrochemical performance compared to that of the pure SCF cathodes. Through optimizing the structures of composite cathodes, the cathodic overpotential of triple-layer SCF-LDC composite cathodes was only 23 mV at 0.3 A cm^-2. The specific ohmic resistance, charge transfer resistance and gas phase diffusion resistance of the triple-layer SCF-LDC cathodes were the lowest for the SCF-LDC composite cathodes, and they were 0.1 Ω cm², 0.01 Ω cm² and 0.1 Ω cm² respectively at 800 °C. The changes were attributable to the enlargement of triple phases boundary (tpb) and enhancement of the adhesion between electrode and electrolyte by adding LDC to the cathode material.