Effect of mixed-conducting interfacial layers on solid oxide fuel cell anode performance

The interfacial resistance of Ni-Y2O2-stabilized ZrO2 (Ni-YSZ) anodes on YSZ electrolytes has been reduced by inserting thin interfacial layers of TiO2-doped YSZ (YZT) or Y2O3-doped CeO2 (YDC). Impedance spectroscopy measurements at temperatures ranging from 600 to 750 degrees C typically showed a high frequency are (HFA) and a low frequency are (LFA). The HFA was reduced by the addition of either interlayer, with a larger reduction for YDC. This presumably resulted from enhanced charge transfer due to the mixed conductivity and/or enhanced redox reaction rate of the interfacial layer. The LFA, which was apparently related to mass-transport processes, grew with decreasing YSZ surface roughness and increasing interlayer thickness. The overall interfacial resistance was minimized for layer thicknesses of -0.5 mu m. The lowest interfacial resistances in 97% H-2 + H2O, 0.13 Omega cm(2) at 750 degrees C, and 0.29 Omega cm(2) at 600 degrees C, were obtained with 0.5 mu m thick YDC interfacial layers.