The oxide composition LaSr 2 Fe 2 CrO 9−␦ was tested for application as an anode material for solid oxide fuel cells. Despite the high Fe content, this composition was found to be stable under SOFC anode conditions up to ϳ800°C. The composite anode LaSr 2 Fe 2 CrO 9−␦ -Gd 0.1 Ce 0.9 O 2−␦ was tested in Gd 0.1 Ce 0.9 O 2−␦ and La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3−␦ electrolyte-supported cells in air and humidified H 2 . The maximum power density was Ϸ365 mW/cm 2 at 800°C, with a corresponding total cell resistance of Ϸ0.69 ⍀ cm 2 . However, the anode polarization resistance at 800°C was Ϸ0.25 ⍀ cm 2 .Ni-yttria stabilized zirconia ͑YSZ͒ cermets are commonly used in solid oxide fuel cell ͑SOFC͒ anodes because of their excellent electrochemical performance in hydrogen fuel. However, nickel is susceptible to sulfur poisoning and carbon coking, which are detrimental to anode performance. 1,2 In order to avoid the challenges associated with Ni metal, several groups have studied conducting oxide materials for application as SOFC anodes. The most successful anodes, in terms of electrochemical performance, have been mixed oxygen-ion and electronically conducting oxides. For example, SOFCs with anodes consisting of the mixed conducting perovskite, La 0.75 Sr 0.25 Cr 0.5 Mn 0.5 O 3−␦ , yielded a power density of 0.57 W/cm 2 at 800°C with hydrogen fuel. 3 Recently, a double perovskite, Sr 2 MgMoO 6−␦ , was reported to yield a maximum power density of 0.84 W/cm 2 at 800°C with hydrogen fuel and good sulfur tolerance. 4,5 Tao and Irvine have reported that the Cr/Fe-B site perovskite, La 0.75 Sr 0.25 Cr 0.5 Fe 0.5 O 3−␦ , functions as a stable SOFC anode in H 2 fuel and it is a catalyst for methane reforming and oxidation. 6 Kozhevnikov et al. characterized, in detail, the mixed conductor, LaSr 2 Fe 2 CrO 9−␦ ͑LSFeCr͒, with an oxygen-ion conductivity of 0.03 S/cm at 750°C. 7 LSFeCr was shown to be stable at oxygen partial pressures as low as ϳ10 −21.5 atm at 750°C, 7 which is similar to the operating conditions of intermediate temperature SOFC anodes.In this paper, the electrochemical performance of composite anodes containing LSFeCr and Gd 0.1 Ce 0.9 O 2−␦ ͑GDC͒ were assessed in GDC and La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3−␦ ͑LSGM͒ electrolyte-supported SOFCs. GDC was included in the anode because it can decrease the polarization resistance 8 by introducing triple-phase boundaries and/or providing high-ionic-conductivity pathways within the anode. The anodes were examined after fuel cell testing in order to check their stability in reducing anode conditions.
ExperimentalLSFeCr was synthesized by solid-state reaction at 1250°C for 24 h with intermittent grindings. The starting materials were was precalcined at 800°C for 4 h to remove all hydroxides. After the synthesis, LSFeCr was attrition milled for 4 h in order to reduce the particle size.Cell tests were performed on GDC and LSGM electrolyte supported cells. GDC electrolytes were prepared by uniaxially pressing nanoscale GDC ͑Nextech͒ and sintering at 1400°C for 6 h, yielding ϳ300 m th...