Ba0.5Sr0.5Co0.8Fe0.2O3-δ-based dual-gradient cathodes for solid oxide fuel cells

Abstract

Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF)/Gd0.2Ce0.8O1.9 (GDC) dual-gradient cathodes for solid oxide fuel cells (SOFCs) were prepared via a spraying-sintering route, using corn starch as a pore-forming agent. The X-ray diffraction (XRD) analysis results revealed that the BSCF and GDC showed good chemical compatibility even at 1200°C. The scanning electron microscopy (SEM) results indicated that a graded pore structure, in addition to a gradient composition, can be obtained by regulating the dosage of the pore-forming agent. Consequently, the dual-gradient cathode possessed a low polarization resistance of 0.25Ωcm2 at 750°C, when the pore-forming agent contents were graded at 5wt%, 10wt%, and 15wt% from the inner sub-layer to the outer sub-layer, respectively. This comparative study indicated that high levels of porosity are beneficial for oxygen transport; however, the variation in the porosity of the adjoining sub-layers should be tailored to guarantee the provision of continuous conductive paths for charge carriers.