Effect of cobalt-substitution Sr2Fe1.5-xCoxMo0.5O6-δ for intermediate temperature symmetrical solid oxide fuel cells fed with H2-H2S

Abstract

Double-perovskite Sr2Fe1.5Mo0.5O6-δ 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-δ (SFCM, x=0, 0.5, 0.75 and 1) were synthesized in this work. XRD, BET, XPS, PL, O2-TPD (H2-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 30.51nm, as well as the larger BET surface areas 9.51 m2/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 δ=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°C. Sample x=0.5 with the lowest conductance activation energy 0.42eV 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% H2 at 800°C.