EXCHANGE CURRENT DENSITIES OF Pt/YSZ OXYGEN ELECTRODES AS A FUNCTION OF YTTRIA CONTENT IN YSZ ELECTROLYTE

摘要

Porous Pt electrodes sintered on YSZ disks containing various Y_2O_3 contents were polarized in an anodic direction by the application of rectangular potential pulses at 400℃. The current decay curves obtained were resolved into two decay curves in terms of the time constant. The faster decay component gave the polarization vs. log i plots which fit Tafel's law with a slope of 267 mV/decade corresponding to one-electron transfer reaction. The associated capacitance per actual contact area was found to be on the order of 10 μF/cm~2, which agrees with the true double layer capacitance estimated from the parallel plate condenser model. These findings suggest that the polarization of faster decay is a pure charge-transfer polarization, which is most likely due to the reaction O~2→O~-+e~-. The exchange current density obtained by extrapolating the η vs. log i plots increases with increasing conductivity of the electrolyte used.