Investigation of the mixed conducting oxide Sc_0.15Y_0.05Zr_0.62Ti_0.18O_1.9 as a potential SOFC anode material

Electrochemical current-potential and impedance measurement techniques have been applied to a ceramic anode based on the mixed electronic and oxide ion conductor Sc(0.15)Y(0.05)Zr(0.62)Ti(0.18)O(1.)9 (ScYZT). Significantly better performance is obtained with this anode using a platinum current collector than for platinum on its own or platinum applied to a porous yttria-stabilized zirconia interlayer. Indeed the polarization resistance of ScYZT is 5.66 Omega cm(2) at open circuit-voltage at 900 degreesC in wet 5% H-2 which is ten times lower than for platinum under the same conditions. Impedance spectroscopic measurements show a number of phenomena attributed to a combination of the electronic resistance through the anode, the oxide ionic current exchange between anode and electrolyte, and noncharge chemical processes at the anode. It was found that interface and chemical impedances change with changes in the electronic conductivity of ScYZT when different bias potentials are applied, although the overall chemical impedance was not observed to change significantly. These measurements suggest that ScYZT is a promising anode material for use with an appropriate current collector. (C) 2004 The Electrochemical Society.