Transition Behavior for O[sub 2] Reduction Reaction on (La,Sr)MnO[sub 3]∕YSZ Composite Cathodes of Solid Oxide Fuel Cells

Electrochemical behavior of the oxygen reduction reaction on (LSM/YSZ) composite and Gd-doped (GDC)-impregnated LSM electrodes was investigated in the absence and presence of a Fe-Cr alloy at in air. The results indicate that for the reduction on the LSM-based composite electrodes there is an electrochemical transition from a dominant electronic conducting LSM electrode to that of the mixed ionic and electronic conducting (MIEC) oxide such as (LSCF) as the YSZ content in the LSM/YSZ composites increases. Such a transition occurs at a YSZ content well below the percolation limit of the ionic connectivity of the LSM/YSZ composites. This indicates that addition/impregnation of ionic conducting phases such as YSZ and GDC not only enhances the three phase boundary but also significantly promotes the surface exchange processes for the reduction reaction on the LSM-based composite cathodes.