Oxygen Diffusion and Surface Exchange Coefficients of Porous La0.6Sr0.4Co0.2Fe0.8O3-δ Decorated with Co3O4 Nanoparticles

This work presents a comparative study of the diffusion (D-chem) and surface exchange coefficients (k(chem)) delta of porous La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF) and Co3O4 nanoparticles decorated LSCF electrodes. The study was carried out using the 3DT-EIS method, which combines Electrochemical Impedance Spectroscopy experiments with FIB-SEM tomography data through an adapted Transmission Line-Adler Lane Steele electrochemical model.A reduction of the polarization resistance of about 60% was measured for the Co3O4 decorated LSCF respect to the reference LSCF cathode, in air at 700 degrees C. The Co3O4 decoration was found to modify the ORR surface reaction limiting mechanism from O-2 dissociation to O-ion incorporation, whereas the diffusion coefficient was not modified by the decoration, which represents a surface diffusion process for both electrodes. After the EIS measurements, the Co3O4 particles were almost no longer visible by Field-Emission SEM on the surface of the decorated sample, but signs that these particles play an active role in Sr Segregation were observed by STEM-EDS, in particular by concentrating the segregated SrO in the surroundings of the decorated particles. (C) 2022 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.