Preparation and evaluation of Ca3-xBixCo4O9-delta (0 < x <= 0.5) as novel cathodes for intermediate temperature-solid oxide fuel cells

Abstract

The misfit compounds Ca3-xBixCo4O9-delta (x = 0.1-0.5) were successfully synthesized via conventional solid state reaction and evaluated as cathode materials for intermediate temperature-solid oxide fuel cells. The powders were characterized by X-ray diffraction, scanning emission microscopy, X-ray photoelectron spectroscopy, thermogravimetry analysis and oxygen-temperature programmed desorption. The monoclinic Ca3-xBixCo4O9-delta powders exhibit good thermal stability and chemical compatibility with Ce0.8Sm0.2O2-gamma electrolyte. Among the investigated single-phase samples, Ca2.9Bi0.1Co4O9-delta shows the maximal conductivity of 655.9 S cm(-1) and higher catalytic activity compared with other Ca3-xBixCo4O9-delta compositions. Ca2.9Bi0.1Co4O9-delta also shows the best cathodic performance and its cathode polarization resistance can be further decreased by incorporating 30 wt.% Ce0.8Sm0.2O2-gamma. The maximal power densities of the NiO/Ce0.8Sm0.2O2-gamma anode-supported button cells fabricated with the Ce0.8Sm0.2O2-gamma electrolyte and Ca2.9Bi0.1Co4O9-delta + 30 wt.% Ce0.8Sm0.2O2-gamma cathode reach 430 and 320 mW cm(-2) at 700 and 650 degrees C respectively. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.