Evaluation of Ca Doped La_0.2Sr_0.7TiO₃as an Alternative Material for Use in SOFC Anodes

Abstract

Doped strontium titanates have been widely studied as potential anode materials in solid oxide fuel cells (SOFCs). The high n-type conductivity that can be achieved in these materials makes them well suited for use as the electronically conductive component in SOFC anodes. This makes them a potential alternative to nickel, the presence of which can be a major cause of degradation due to coking, sulfur poisoning and low tolerance to redox cycling. Here anode performance results are presented for an A-site deficient strontium titanate co-doped with lanthanum and calcium on the perovskite A-site, La0.20Sr0.25Ca0.45TiO3 (LSCTA-). LSCTA- anodes and LSM cathodes were screen printed on 160 μm thick 6-ScSZ electrolyte supports. The LSCTA- anode backbone showed poor electrode performance, but its conductivity was sufficient to keep ohmic losses low. Upon impregnation with combinations of ceria and nickel, ohmic losses and polarization impedances are significantly reduced, resulting in a drastic improvement in anode performance. Unexpectedly, the performance of cells impregnated with both ceria and nickel showed an improvement upon redox cycling. A stable area specific resistance of 0.37 Ωcm2 was achieved after 20 redox cycles and 250 hours of operation at 900°C in H2 with 8% H2O, showing excellent redox stability.