Quantitative Evaluation of Electrochemically Active Area in an SOFC Cathode by Oxygen Isotopic Exchange Measurements of a Model Patterned Electrode

The electrochemically active area in an SOFC cathode was quantitatively evaluated from 18O/16O isotope exchange with/without polarization and following isotopic distribution analysis by second ion mass spectroscopy. For this purpose, we proposed a patterned dense thin film electrode modelling a columnar SOFC cathode, and was fabricated it with La0.6Sr0.4CoO3-δ on a Ce0.9Gd0.1O1.95-δ electrolyte. Compared with the results under open circuit condition, the increase in the isotopic ratio of 18O was observed near the electrode/electrolyte interface when a cathodic bias was applied. Such an increase in the 18O isotopic ratio was considered due to the electrochemical oxygen incorporation. The electrochemically active area was evaluated as approximately 25 μm in the La0.6Sr0.4CoO3-δ patterned thin film electrode under cathodic polarization of 220 mV in P(O2) = 1 bar at 973 K