Oxygen Diffusion and Surface Exchange Coefficients of Porous La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ Decorated with Co 3 O 4 Nanoparticles

ASCOLANI-YAEL, JULIAN; MONTENEGRO-HERNANDEZ, ALEJANDRA; BAQUÉ, LAURA C.; TOSCANI, LUCÍA M.; CANEIRO, ALBERTO; MOGNI, LILIANA VERONICA

JOURNAL OF THE ELECTROCHEMICAL SOCIETY

ELECTROCHEMICAL SOC INC

Año: 2021

0013-4651

This work presents a comparative study of the diffusion (Dchem) and surface exchange coefficients (kchem) of porous La0.6Sr0.4Co0.2Fe0.8O3-δ (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 °C. The Co3O4 decoration was found to modify the ORR surface reaction limiting mechanism from O2 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.