Comparison of the Electrochemical Properties of Infiltrated and Functionally Gradient Sm0.5Sr0.5CoO3-δ-Ce0.8Sm0.2O1.9 Composite Cathodes for Solid Oxide Fuel Cells

This study investigates the electrochemical properties of three different configurations of Sm0.5Sr0.5CoO3-delta (SSC)-based cathodes and attempts to discover a potential approach applicable to solid oxide fuel cells (SOFCs). The functionally gradient SSC cathode and Ce0.8Sm0.2O1.9 (SDC)-infiltrated SSC cathode both reveal the better electrochemical properties compared to that of the 70 SSC-30 SDC composite cathode. The functionally gradient Sm0.5Sr0.5CoO3-delta cathode with better interface of SSC/SDC may be achieved by the gradual change in composition from electrolyte to cathode, resulting in the decline in charge transfer resistance and gas phase diffusion resistance. Whereas, the dramatic decrease in cathode polarization resistance for SDC-infiltrated SSC cathode is mainly attributed to the creation of SDC/SSC phase boundaries. The newly formed SDC on the SSC surface with highly porous would allow gas-phase molecules to easily diffuse to the SDC/SSC boundaries, which considerably increase the electrochemical sites for oxygen reduction reaction (ORR). The SDC-infiltrated SSC cathode reveals the lowest cathode polarization resistance (R-P), the lowest activation energies of cathode polarization resistance and the lowest over activation energy for the ORR among all cathode configurations. Noticeably, the cathode performance in SOFCs can be significantly improved by infiltrating nanoparticles of SDC into an SSC porous backbone. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.017206jes] All rights reserved.