Solid oxide fuel cell cathodes prepared by infiltration of LaNi_(0.6)Fe_(0.4)O_3 and La_(0.91)Sr_(0.09)Ni_(0.6)Fe_(0.4)O_3 in porous yttria-stabilized zirconia

摘要

SOFC composite electrodes of yttria-stabilized zirconia (YSZ) and either LaNi_(0.6)Fe_(0.4)O_3 (LNF) or La_(0.91)Sr_(0.09)Ni_(0.6)Fe_(0.4)O_3 (LSNF) were prepared by infiltration to a loading of 40wt% of the perovskite into porous YSZ using aqueous solutions of the nitrate salts. XRD measurements indicated that the perovskite structures were formed following calcination at 850℃, at which temperature the LNF and LSNF form small particles that coat the YSZ pores. Heating to 1100℃ causes the particles to form a dense film over the YSZ but caused no solid-state reaction. Calcination of an LNF-YSZ composite to 1200℃ led to an expansion of the LNF lattice, suggesting introduction of Zr(lV) into the perovskite; further heating to 1300℃ caused the formation of La_2Zr_2O_7. For 850℃ calcination, the electrode performance of both LNF-YSZ and LSNF-YSZ composites was similar to that reported for composites of YSZ and La_(0.8)Sr_(0.2)FeO_3 (LSF), with a current-independent impedance of approximately 0.1 Ω cm~2 at 700℃ in air. For 1100℃ calcination, both LNF-YSZ and LSNF-YSZ composites exhibited impedances that decreased strongly under both anodic and cathodic polarization. The implications of these results for preparing electrodes based on LNF and LSNF are discussed.