Properties of A-site nonstoichiometry (Pr0.4)xSr0.6Co0.2Fe0.7Nb0.1O3-σ(0.9 ≤ x ≤ 1.1) as symmetrical electrode material for solid oxide fuel cells

In order to solve the carbon deposition and sulfur adsorption problems during operations of solid-oxide fuel cells (SOFCs), (Pr-0.4)(x)Sr0.6Co0.2Fe0.7Nb0.1O3-sigma (PxSCFN, x = 0.9, 0.95, 1.0, 1.05 and 1.1) oxides are synthesized by the solid state reaction method and investigated as both cathode and anode for SOFCs. For PxSCFN (x = 0.9-1.05) powders, it is found that cubic perovskite phase is formed after sintering at 1050 degrees C; however, when x increases to 1.1, a single impurity phase is detected for PxSCFN sample by X-ray diffraction. The effects of A-site nonstoichiometry on thermal expansion coefficient, electrical conductivity and polarization resistance are investigated. The excess of A-site Pr elements in PxSCFN (x = 1.05 and 1.1) results in a decrease in grain size and the creation of more active sites for oxygen reduction reaction. AC impedance reveals that P1.05SCFN as symmetrical electrodes has the best electrochemical catalytic performance both in O-2 and in wet H-2 atmosphere. The maximum power densities of a P1.05SCFN/LSGM/P1.05SCFN cell reach as high as 1.13 W cm(-2) in wet H-2 and 0.67W cm(-2) in wet CH4 at 900 degrees C. Therefore, PLosSCFN is a potential symmetrical electrode material for SOFCs. (C) 2013 Elsevier B.V. All rights reserved.