Electrochemical properties of La_0.8Sr_0.2FeO_3-δ based composite cathode for intermediate temperature SOFC

La_0.8Sr_0.2FeO_3-δ is a new kind of cathode material for intermediate SOFC, but its electrochemical activity is relative poor for the lanthanum gallate based solid oxide fuel cell. In this paper, a novel composite cathode of La_0.8Sr_0.2 FeO_3-δ/La_0.9 Sr_0.1Ga_0.8 Mg_0.2O_3-δ was prepared on the LSGM electrolyte substrate by screen-printing method. The results of cathodic polarization measurements show that the overpoten-tial decreases significantly when the composite cathode is used instead of the La_0.8Sr_0.2FeO_3-δ single layer cathode. The cathodic overpotential of the composite La_0.8Sr_0.2 FeO_3-δ/La_0.9 Sr_0.1Ga_0.8Mg_0.2O_3-δ cathode is 150 mV at the current density of 0.2 A·cm^-2 at 800°C,, while the cathodic overpotential of the La_0.8Sr_0.2FeO_3-δ single layer cathode is higher than 260 mV at the same condition. The electrochemical impedance spectroscopy was employed to investigate the polarization resistance of the cathode. The polarization resistance of the composite cathode is 1.20 Ω·cm² in open circuit condition, while the value of the single La_0.8Sr_0.2 FeO_3-δ cathode is 1.235 Ω·cm².