Characterizations of LBC-GDC Composite Cathodes for Low Temperature SOFCs

This study reports on the physico-electro-chemical characterization of porous composite electrodes made of lanthanum-barium-cobalt oxide (LBC) electrocatalyst and gadolinium-doped-cerium oxide (GDC) oxygen-ion conductor. Four different compositions of LBC-GDC composite electrodes were fabricated and heat-treated at 1150 degrees C. The phase purity of the heat-treated LBC-GDC composite was checked by X-ray diffraction measurements. Thermal expansion coefficient (TEC) was measured from room temperature to 900 degrees C. Porous LBC-GDC composite electrodes were studied in a symmetrical cell configuration by impedance spectroscopy where gadolinium doped ceria (GDC) was used as a solid electrolyte. Impedance spectra obtained at zero dc bias conditions consisted of two semi-circular arcs, which indicate that the overall oxygen reduction comprises at least two distinct processes. The area specific resistance (ASR) for electrode polarization was measured in the 600-800 degrees C temperature ranges. The lowest ASR value of 0.06 Omega cm(-2) at 600 degrees C was exhibited by LBC/GDC composite of composition 60/40. The ASR values at lower temperatures offer the promise of utilizing composite as a cathode for low-temperature SOFCs. VC 2011 The Electrochemical Society. [DOI: 10.1149/1.3606475] All rights reserved.