Sc-substituted oxygen excess titanates as fuel electrodes for SOFCs

A new family of perovskite-based materials La2Sr4Ti6-xScxO19-z has been investigated in the search of alternative anodes for solid oxide fuel cells (SOFCs). Although these phases show a pseudocubic unit cell (a approximate to 3.91 angstrom) by X-ray diffraction, the structure is far more complex with extra oxygen beyond the ABO(3) perovskite stoichiometry accommodated in local defects randomly distributed within a perovskite framework. The presence of Sc has a negative effect on the electronic conductivity, which gradually decreases with increasing x, although the oxidation and reduction kinetics is improved. The fuel cell performance, however, is improved in comparison to reported results for the nonsubstituted phases at low levels of substitution. Anodic polarization overpotentials of 0.25 and 0.30 V at 500 mA cm(-2) at 900 degrees C under wet H-2 and CH4, respectively, were obtained for the x=0.3 composition. The relatively low overpotential, especially under methane, indicates this to be a promising approach toward anode development. (c) 2005 The Electrochemical Society. All rights reserved.