Electrochemical Reaction Mechanism of LSM-YSZ Composite Cathode Based on 3D Simulation of Oxygen Diffusion and Oxygen Labeling Experiment

Electrochemical reaction mechanism of an LSM-YSZ composite cathode is investigated using a combined measurement of oxygen labeling experiment and 3D numerical simulation using a reconstructed microstructure. First, an oxygen labeling experiment was conducted using 18O2 at 750°C under polarized condition. Then, a three-dimensional microstructure was obtained using a focused ion beam-scanning electron microscopy (FIB-SEM). Secondary ion mass spectroscopy (SIMS) analysis was conducted at the middle plane of the measured volume to correlate 18O distribution with the 3D microstructure. Using the 3D microstructure, electrochemical simulation was carried out considering the oxygen potential dependence of LSM ionic conductivity. Then, 18O transport was solved considering the balance between diffusion by concentration gradient, ionic current transport, and production by reaction current. The electrochemical reaction mechanism was discussed by comparing the numerically solved 18O concentration with that obtained from oxygen labeling experiment.