Double-perovskite Sr2Fe1.5Mo0.5O6-delta with high performance has been investigated as potential symmetrical electrode materials for Solid Oxide Fuel Cells (SOFCs). In order to enhance its catalytic activity and electrochemical performance, a series of cobalt-substituted Sr2Fe1.5-xCoxMo0.5O6-delta (SFCM, x=0, 0.5, 0.75 and 1) were synthesized in this work. XRD, BET, XPS, PL, O-2-TPD (H-2-TPR), SEM and electrochemical performance tests have been conducted to characterize the improved performances. XRD and BET measurements indicate SFCM with the double-perovskite structure, and smaller grain size is 30.51 nm, as well as the larger BET surface areas 9.51 m(2)/g for cobalt-rich sample x=0.75. The redox couples Fe3+/Fe2+, Co3+/Co2+ and Mo6+/Mo5+ are revealed by XPS, and more oxygen vacancy delta=0.46 is detected by PL and iodometry for sample x=0.75, which is conducive to the redox catalytic activity and ionic conductivity yielding highest 59.48 S.cm(-1) at 800 degrees C. Sample x= 0.5 with the lowest conductance activation energy 0.42 eV also exhibits best electrochemical performance with the highest power density of 42.6 mW.cm(-2) for the configuration of SFCM/LSGM/SFCM in 0.5% H2S-3% H-2 at 800 degrees C. (C) 2014 Elsevier Ltd. All rights reserved.