Electrochemical characteristics of samaria-doped ceria infiltrated strontium-doped LaMnO₃ cathodes with varied thickness for yttria-stabilized zirconia electrolytes

Samaria-doped ceria (SDC) infiltrated into strontium-doped LaMnO ₃ (LSM) cathodes with varied cathode thickness on yttria-stabilized zirconia (YSZ) were investigated via symmetrical cell, half cell, and full cell configurations. The results of the symmetrical cells showed that the interfacial polarization resistance (R_P) decreased with increasing electrode thickness up to ∼30 μm, and further increases in the thickness of the cathode did not cause significant variation of electrode performance. At 800 °C, the minimum R_P was around 0.05 Ω cm². The impedance spectra indicated that three main electrochemical processes existed, possibly corresponding to the oxygen ion incorporation, surface diffusion of oxygen species and oxygen adsorption and dissociation. The DC polarization on the half cells and characterization of the full cells also demonstrated a similar correlation between the electrode performance and the electrode thickness. The peak power densities of the single cells with the 10, 30, and 50-μm thick electrodes were 0.63, 1.16 and 1.11 W cm^-2, respectively. The exchange current densities under moderate polarization are calculated and possible rate-determining steps are discussed.