Visualization of oxygen transport behavior at metal electrode/oxide electrolyte interface using secondary ion mass spectrometry

The tracks of oxygen transport around platinum or gold electrode/yttria stabilized zirconia (YSZ) electrolyte interface were visualized by oxygen isotope (¹⁸O) labeling (T = 773-973 K, p(O₂) = 7 kPa, cathodic polarization E = 0 or - 0.3 V) and multi dimensional imaging using secondary ion mass spectrometry (SIMS). The activation of oxygen exchange reaction was clearly observed as a strong ¹⁸O^- intensity at metal/YSZ interface treated at T = 973 K indicating that the reaction dominantly occurs at gas/electrode/electrolyte triple phase boundary (TPB). Platinum/YSZ interface exhibited a stronger ¹⁸O^- intensity than gold/YSZ, however, the intensity distribution was not homogenous. The effect of applying cathodic polarization on the oxygen transport was more clearly observed at gold/YSZ interface than platinum/YSZ. The cause of differences in experimental results is discussed in connection with the different reaction controlling process among the two electrodes materials.