The polarization phenomena of the O-2-Pd-YSZ interface were studied as a function of oxygen partial pressure (1-100 kPa) and temperature (400-550 degreesC) in the double chamber reactor cell: Pd/YSZ/Pd. The steady-state current-overpotential characteristics can be analyzed with a Butler-Volmer type of equation. The apparent anodic and cathodic charge transfer coefficients are found close to 0.5 and the activation energy of the exchange current was found to he about 107 kJ/mol. Based on the experimental results, a charge transfer reaction model, is proposed.