Imaging of oxygen transport at SOFC cathode/electrolyte interfaces by a novel technique

Oxygen transport was examined around the O₂/cathode/yttria-stabilized zirconia (YSZ) interfaces in solid oxide fuel cells (SOFCs). To visualize the kinetics of oxygen transport, isotope oxygen exchange (¹⁶O/¹⁸O exchange) and secondary ion mass spectrometry analysis (SIMS) were adopted for La_0.85Sr_0.15MnO₃-mesh and gold (Au)-mesh cathodes. The mesh cathode surfaces promoted oxygen adsorption and surface oxygen exchange. Oxygen bulk diffusion in the mesh cathode was observed only at the La_0.85Sr_0.15MnO₃-mesh. The active sites for oxygen incorporation were compared at the YSZ surfaces after removing the mesh cathodes. The La_0.85Sr_0.15MnO₃-mesh/YSZ interface can be the active site for oxygen incorporation as well as the triple phase boundary (TPB). On the other hand, the Au/YSZ interface showed low ¹⁸O concentration, and the active sites were limited to the TPB lines. Most active sites for oxygen incorporation were the O₂/cathode/YSZ interface (TPB) for La_0.85Sr_0.15MnO₃-mesh and Au-mesh from the line analysis of the SIMS images. The expansion of the oxygen incorporation active site around the TPB was discussed on the basis of SIMS imaging analysis and electrochemical analysis.