Study on impedance spectra of La0.7Sr0.3MnO3 and Sm0.2Ce0.8O1.9-impregnated La0.7Sr0.3MnO3 cathode in single chamber fuel cell condition

Impedance spectroscopy was used to study the electrochemical performance of pure and ion-impregnated La_0.7Sr_0.3MnO₃ (LSM) cathodes on YSZ (Y₂O₃-stabilized ZrO₂) electrolytes in single chamber fuel cell conditions, i.e. a mixture gas with oxygen as oxidant, methane as fuel and nitrogen as dilute gas. Measurements were taken at the furnace temperature range of 550-750 °C and the CH₄/O₂ ratios from 1 to 2. Polarization resistances (R_p) for pure and impregnated LSM cathodes increased obviously as the CH₄/O₂ ratio increased at 650-750 °C. Polarization resistances of Sm_0.2Ce_0.8O_1.9 (SDC) impregnated LSM cathode were much smaller than the ones of pure LSM cathode under the same conditions. Overtemperatures were occurred at both cathodes due to the partial oxidation of methane.