Pt-cermet cathode for reduced temperature SOFCs

Polarization characteristics of Pt–(Sc0.10Ce0.01)Zr0.89O2 (SSZ) cermet cathodes were studied in order to develop new cathodes for reduced temperature solid oxide fuel cells (SOFCs). Several Pt–SSZ cermet electrodes were prepared by mixing Pt and SSZ powders using a high-energy ball mill. A Pt–SSZ cermet cathode on yttria-stabilized zirconia (YSZ) electrolyte achieved high cathodic activity; the cathode interfacial conductivity reached as high as 6.7 S/cm2 at 973 K and 0.8 S/cm2 at 873 K. These results suggest that this Pt–SSZ cermet cathode has enough capability at 973 K, but is still not satisfactory at 873 K. This high activity can be obtained by ball milling SSZ/Pt mixture of proper ratios in vacuum and by controlling electrode thickness, sintering temperature, and Ca impurity. These electrodes showed two optima of interfacial conductivity vs. SSZ/Pt ratio and remarkable dependence on cathode thickness. It was considered that the first optimum is based on two-dimensional reaction sites on YSZ electrolyte surface and the second one originates from three-dimensional expansion of reaction sites into the cermet cathode.