Highly active and stable (La0.24Sr0.16Ba0.6)(Co0.5Fe0.44Nb0.06)O3−δ (LSBCFN) cathodes for solid oxidefuel cells prepared by a novel mixing synthesis method

Abstract

Lanthanum and/or barium strontium cobalt ferrite perovskite oxide materials are highly active cathodes for solid oxide fuel cells (SOFCs) operated at intermediate temperatures of 600–900 °C. However, they are vulnerable to degradation by chromium deposition and poisoning by volatile Cr species from chromia-forming metallic interconnects. Here we report the development of a new mixed ionic and electronic conductor, lanthanum strontium barium cobalt ferrite niobium perovskite, (La_0.24Sr_0.16Ba_0.6)(Co_0.5Fe_0.44Nb_0.06)O_3−δ (LSBCFN), prepared by a novel direct mixing synthesis of (La_0.6Sr_0.4)(Co_0.2Fe_0.8)O_3−δ (LSCF) and Ba(Co_0.7Fe_0.2Nb_0.1)O_3−δ (BSCN). The electrical conductivity of LSBCFN is 124 S cm⁻¹ at 600 °C, which is significantly higher than 11 S cm⁻¹ measured on BSCN at the same temperature. The new LSBCFN cathode which combines the structural stability and activity of BCFN and the high conductivity of LSCF not only exhibits better electrochemical activity for the O₂ reduction reaction than either LSCF or BCFN in the temperature range of 600–900 °C, but most importantly, it shows excellent stability and tolerance toward chromium deposition and poisoning under SOFC operation conditions. A semi-quantitative analysis indicates that the Cr deposition at the electrode is closely related to the surface segregation of Sr and Ba.