SMART catalyst based on doped Sr-titanite for advanced SOFC anodes

Abstract

B1403To increase the durability of SOFC stacks, robust anodes with high catalytic performance and redox tolerance are needed. Among all alternatives, La-doped strontium titanate (LST) materials were recognized to possess good electronic conductivity and high tolerance to redox cycles1,2, but modest electro-catalytic activity, which can be enhanced in conjunction with an appropriate catalyst. Nevertheless, anodes with conventional composite microstructures (e.g. LST with equally sized Ni-phase) are still prone to sulphur poisoning, coking and to coalescence of the Ni phase over time. The authors present recent advances of a SMART material concept with a catalytic and microstructural self-regeneration effect, in which nanosized nickel catalyst is repeatedly exsolved from and incorporated back into the LST perovskite host structure. Ni-nanoparticles are exsolved from LST at low pO2 (i.e. at SOFC anode conditions) and the Ni is re-incorporated hat high pO2. Since titanates are highly tolerant to changes of the oxygen partial pressure, application of controlled redox cycles could therefore lead to the burn-off of harmful sulphides and/or carbon deposits and at the same time the incorporation-exsolution cycles also help circumventing the catalysts coarsening problem. We present the concept in which Ni-doped LST is applied to repetitively exsolute and re-incorporate the Ni catalyst, hence offering a microstructural self-regeneration mechanism