Reaction Sites of Mixed Conductor Anodes in Solid Oxide Fuel Cells

Pt pattern anodes with defined TPB length were prepared on the surface of YSZ or SDC (samaria-doped ceria) interlayer deposited on an YSZ disk, in order to investigate the reaction sites of SOFC anodes consisting of mixed conductor oxides. The electrode resistance was measured by AC impedance method under different conditions and assigned to reaction resistances by fitting to an equivalent circuit. The dependence of the reaction resistances was investigated by varying operation temperature, hydrogen partial pressure, and the number of the Pt electrode patterns. The impedance in the Nyquist plots was fitted by two semicircles at low and high frequencies, and the high frequency arc was assigned to the anodic reactions nearby the TPB. For the same TPB length, the conductivity determined from the high frequency arc for the Pt electrodes on the SDC layer was almost ten times as large as that on the YSZ layer.