Characterization and evaluation of Ba-doped BaxSr1-xCo0.9Sb0.1O3-δ as cathode materials for LaGaO3-based solid oxide fuel cells

BaxSr1-xCo0.9Sb0.1O3-delta (BSCSbx, x = 0.0-0.8) are investigated as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs). BSCSbx oxides are crystallized in a tetragonal structure with s.g. P4/mmm. XPS analysis shows that Ba doping reduces valence state of Co ions: Co in SrCo0.9Sb0.1O3-delta is prone to Co4+, while Co in Ba doped SrCo0.9Sb0.1O3-delta becomes more prone to Co3+. Oxygen deficiency delta increases with Ba doping even at high temperatures. Conductivity is found to decrease with Ba doping. Thermal expansion coefficient (TEC) decreases from 20.6 x 10(-6) K-1 for x = 0.0 to 18.4 x 10(-6) K-1 for x = 0.6 at 30-1000 degrees C. With increasing x from 0.0 to 0.6, polarization resistance (R-p) decreases monotonously, and then increases with further increasing x. The lowest R-p of 0.081 Omega cm(2) at 700 degrees C is obtained for BSCSb0.6 cathode. At 700-850 degrees C, the Rp of BSCSb0.6 is mainly contributed from electron charge transfer; however, below 700 degrees C, ion charge transfer plays a more important role in R-p. Maximum power densities of the cell with BSCSb0.6 cathode on 300-mu m thick La0.9Sr0.1Ga0.8Mg0.2O3-delta (LSGM) electrolyte attain 306-944 mW cm(-2) at 700-850 degrees C. These results indicate that BSCSb0.6 is a promising cathode for application in IT-SOFC. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.