Preparation and characterization of La_(1-x)Sr_xNi_yFe_(1-y)O_(3-σ) cathodes for low-temperature solid oxide fuel cells

摘要

Perovskite-type La_(1-x)Sr_xNi_yFe_(1-y)O_(3-σ) (x = 0.3, 0.4, 0.5, 0.6, y = 0.2; x = 0.3, y = 0.2, 0.3, 0.4) oxides have been synthesized and employed as cathodes for low-temperature solid oxide fuel cells (SOFCs) with composite electrolyte. The segregation of La_2NiO_(4±σ) is observed to increase with the increasing Sr~(2+) incorporation content according to X-ray diffraction (XRD) results. The as-prepared powders appear porous foam-like agglomeration with particle size less than 1 μm. Maximum power densities yield as high as 725 mWcm~(-2) and 671 mWcm~(-2) at 600 ℃ for fuel cells with the LSNF4628 and LSNF7337 composite cathodes. The maximum power densities continuously increase with the increasing Sr~(2+) content in LSNF cathodes, which can be mainly ascribed to the possible charge compensating mechanism. The maximum power densities first increase with the Ni ion incorporation content up to y = 0.3 due to the increased oxygen vacancy, ionic conductivity and oxygen permeability. Further increase in Ni ion content results in a further lowering of fuel cell performance, which can be explained by the association of oxygen vacancies and divalent B-site cations in the cathode.