Electrochemical impedance spectroscopic characterization of impregnated La0.6Sr0.4Co0.2Fe0.8O3-δ cathode for intermediate-temperature SOFCs

The electrochemical performance of the impregnated La0.6Sr0.4Co0.2Fe0.8O3_(delta)-Y2O3 stabilized ZrO2 cathode (LSCF-YSZ) was studied with different amount of LSCF. Function as P-O2. electrode resistance revealed that the rate-determining steps for oxygen reduction were changed with amount of LSCF loading. The rate-determining step is the charge transfer process for 12 wt% LSCF loading cathode. With the increasing amount of LSCF particles on the YSZ scaffold, the rate determining steps are the dissociation of oxygen molecules and adsorption-diffusion of oxygen atom for 20 wt% LSCF loading cathode. Accumulation of a great many LSCF particles on the YSZ scaffold makes the Knudsen diffusion of oxygen molecular of great importance for ORR. The rate-determining step is the Knudsen diffusion for 32 wt% LSCF loading cathode. The mean free path of oxygen molecules is about 0.22-0.27 mu m at 1 atm and the temperature is between 600 and 800 C-degrees. The appearance of inductive loop in the EIS for the cathode with high LSCF loading was possible influenced by the Knudsen diffusion process. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.