The oxygen reduction active sites were visualized around the O
2/SOFC cathode/electrolyte triple phase boundaries (TPB) by the
16O/
18O exchange techniques and secondary ion mass spectrometry (SIMS) analysis. The higher
18O concentration is observed on the cathode top surfaces (La
0.9Sr
0.1MnO
3-mesh, Au-mesh, and Ag-porous), which suggested the promotion of oxygen adsorption and oxygen surface exchange at the cathode.
The oxygen diffusion through the bulk of cathode occurred at the La
0.9Sr
0.1MnO
3-mesh and the Ag-porous cathodes, not at the Au-mesh cathode. On the YSZ surfaces after removing the cathode, the active sites
for oxygen incorporation were analyzed by SIMS. The active sites for oxygen incorporation were at the La
0.9Sr
0.1MnO
3/YSZ interface as well as the TPB. On the other hand, the active sites for oxygen incorporation are limited to the TPB in
the case of the Au-mesh removed YSZ surface. From the SIMS analysis, the expansion of the active sites for oxygen incorporation
is less than a few μm from the TPB lines.
Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.
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