Ag–Zr(Sc)O2 cermet cathode for reduced temperature SOFCs

Polarization characteristics of Ag–(Sc0.10Ce0.01) Zr0.89O2, SSZ, cermet cathodes were investigated in order to develop a new cathode for reduced temperature solid oxide fuel cells, SOFCs. Ag–SSZ cermet cathode was prepared by mixing Ag powder with SSZ powder using a high-energy ball mill in a vacuum and pasting the cermet onto yttria-stabilized zirconia, YSZ, electrolyte. An Ag–SSZ cermet cathode achieved as high as 0.8 S/cm2 of interfacial conductivity, σE, at 773 K in air. Morphology and the σE of this Ag/SSZ cermet cathode were unchanged at 773 K in air by application of cathodic DC bias of 0.5 V. These results suggest that this Ag–SSZ cermet cathode has enough electrode reactivity and durability for a 773-K operating SOFCs for 700 h. This high-electrode reactivity can be originated from an increase of reaction site and a small activation energy, Ea. These results suggested that an Ag–SSZ might be a suitable cathode material for SOFCs operated at 773 K. These observations show the Ag/SSZ ratio for cathode of SOFCs operated at 773 K, suggesting that morphology of cermet would have a large effect on cathode property.