Electrochemical performance of La0.7Sr0.3CuO3−δ–Sm0.2Ce0.8O2−δ functional graded composite cathode for intermediate temperature solid oxide fuel cells

The fabrication and electrochemical properties of graded La0.7Sr0.3CuO3−δ–Sm0.2Ce0.8O2−δ (LSCu–SDC) composite cathodes were investigated in this paper. The phase composition, microstructure and electrochemical properties of the electrodes were characterized using X-ray diffraction (XRD), electron microscopy, electrochemical impedance spectroscopy (EIS) and cathodic polarization examinations. The results showed that the triple-layer graded cathode had super electrochemical performance comparing with the monolayer cathode. The graded LSCu–SDC cathode showed a polarization resistance of 0.094 Ωcm2, a value much lower than the monolayer LSCu cathode of 0.234 Ωcm2 at 800 °C in air. The current density of the graded cathode was 0.341 A cm−2, more than double higher than monolayer LSCu of 0.146 A cm−2 at an overpotential of 30 mV. The improved electrochemical performance could be attributed to the improved physical and chemical compatibility of the cathode layers in graded compositions with SDC electrolyte as well as the enlargement of triple-phase boundary for oxygen reduction.