HIGH-TEMPERATURE AIR CATHODES CONTAINING ION CONDUCTIVE OXIDES

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 (Bi2O3)0.7 (Er2O3)0.3 exhibited the expected trend, resulting in a much higher performance than simple Pt/ZrO2 electrodes. However, additions of (ZrO2)0.92(Y2O3)0.08 or (CeO2)0.8 (SmO1.5)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.