This study is an attempt to improve the performance of Pt/ZrO2 high-temperature air cathodes by imitating porous electrodes of liquid electrolyte fuel cells. Ion conductive oxides were introduced into platinum electrodes in expectation of playing the same electrochemical role as the liquid electrolyte penetrating the porous electrodes. The oxide-mixed platinum electrodes prepared were modeled on a pore whose inner wall was covered with a gas permeable electrolyte film. An analysis based on the pore model predicted that the performance increases with increasing electrode thickness. Electrodes containing (Bi203)0.7 (Er203)0.3 exhibited the expected trend, resulting in a much higher performance than simple Pt/ZrO2 electrodes. However, additions of (ZrO2)0.92(Y203)0.08 or (CeO2)0.8 (SmO1.~)0.2 led to no marked performance improvements. These different effects of oxide additives are explained in terms of the degree of contact between the platinum particles.

The rate constants of electrochemical oxygen reduction by platinum electrodes on various solid oxide electrolytes have been determined from transient depolarization curves and steady-state current-potential curves free of ohmic drop. The rate equations used for the determination were derived on the basis of a mechanism involving dissociation of adsorbed oxygen into atomic species and subsequent diffusion of atomic oxygen through the electrolyte-electrode interface.

017ChemInform Abstract (Y2O3-stabilized ZrO2, Sm2O3-doped CeO2) is carried out by measurements of transient depolarization and steady state polarization curves. The rate equations used for the determination are derived on the basis of a mechanism involving dissociation of adsorbed oxygen into atomic species and subsequent diffusion of atomic oxygen through the electrolyte/electrode interface. Pt paste electrodes are found to be less polarized when sintered on the doped CeO2 electrolyte than on the stabilized ZrO2 electrolyte. The smaller polarization of the CeO2/Pt system is explained by a greater effective reaction area. Addition of pure CeO2 to the ZrO2/Pt system results in a significant decrease in polarization.

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