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 18 O/ 16 O 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 La 0.6 Sr 0.4 CoO 3- δ on a Ce 0.9 Gd 0.1 O 1.95- δ electrolyte. Compared with the results under open circuit condition, the increase in the isotopic ratio of 18 O was observed near the electrode/electrolyte interface when a cathodic bias was applied. Such an increase in the 18 O isotopic ratio was considered due to the electrochemical oxygen incorporation. The electrochemically active area was evaluated as approximately 25 μm in the La 0.6 Sr 0.4 CoO 3- δ patterned thin film electrode under cathodic polarization of 220 mV in P (O 2 ) = 1 bar at 973 K.