Electrochemical performance of LSM-SDC electrodes prepared with ion-impregnated LSM

(La_0.85Sr_0.15)_0.9MnO_3-δ (LSM)-Sm_0.2Ce_0.8O_1.9 (SDC) (50:50 wt.%) composites, which are potential cathodes for intermediate-temperature solid oxide fuel cells, were prepared with a two-step fabricating process including screen-printing and ion-impregnation. SDC frame was screen-printed on electrolyte substrates and LSM was subsequently ion-impregnated to the SDC frame. The interfacial polarization resistances (area specific resistances) of the resulted electrodes were much lower than those prepared with a conventional screen-printing technique and also lower than those with impregnated SDC. At 700 °C, the total resistance was only 0.35 Ω cm² for an LSM-SDC electrode with impregnated LSM compared to 0.94 Ω cm² for a conventional electrode. Impedance spectroscopy was used to study the oxygen reduction kinetics within the electrodes. Three arcs were typically observed on the impedance spectrum. The high-frequency arc was attributed to oxygen ion transfer from the three-phase boundary to the electrolyte, while the intermediate-frequency arc was attributed to oxygen dissociation and adsorption. At high temperature, the arc due to gas phase diffusion was observed in the low frequency region, with size varying as (Po₂)^-0.76 and having low activation energy.