Chemical compatibility, thermal expansion matches and electrochemical performance of SrCo0.8Fe0.2O3−δ–La0.45Ce0.55O2−δ composite cathodes for intermediate-temperature solid oxide fuel cells

The chemical compatibility, thermal expansion and electrochemical property measurements of the SrCo0.8Fe0.2O3−δ (SCF)–La0.45Ce0.55O2−δ (LDC) composite cathodes for solid oxide fuel cells (SOFCs) were investigated by X-ray diffraction (XRD), thermal expansion coefficients (TECs) and cathodic polarization measurements together with electrochemical impedance spectroscopy (EIS). The results indicated that LDC had good chemical compatibility with SCF and La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM), and the addition of LDC to SCF markedly reduced the polarization resistance. When the content of LDC reached 50 wt%, the SCF50 cathode showed the best electrochemical performance, with a cathodic overpotential of 0.1 V at the current density of 1102.0 mA cm−2, together with a polarization resistance of 0.149 Ω cm2 at 800 °C. The improved electrochemical performance was attributed to the expansion of the electrochemical reaction region into the electrode, and offering an easier path for the oxygen ion transport. Furthermore, the SCF–LDC composite cathodes match better with the LSGM electrolyte.

► The chemical and TECs matching of the SCF–LDC cathodes with LSGM are studied firstly. ► Addition of LDC to SCF cathode markedly reduces the polarization resistance. ► Addition of LDC to SCF cathode improves greatly the TECs of cathode to electrolyte. ► The SCF50 is a promising cathode for intermediate-temperature SOFCs.