Effects of Ceria Conductivity on the Oxygen Incorporation at the LSCF-SDC-Gas Three-Phase Boundary

Oxygen incorporation via the three-phase boundaries (3PBs) contributes significantly to the total oxygen reduction reaction on the composite consisting of La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF) and samaria doped ceria (SDC). This work reveals that the reaction rate at the LSCF-SDC-gas 3PBs is affected by the samaria content and reaches the highest value with Sm0.2Ce0.8O2-delta. When the incorporation step, where oxygen species on the surface combines to the oxygen vacancy from SDC, limits the total reaction, the rate can be related directly to SDC conductivity. The rate increases with the conductivity, demonstrating that the incorporation step dominates the total reaction which basically consists of three basic steps: the oxygen molecular adsorption, the dissociation, and the incorporation. In addition, the 3PB contribution is notably affected by the samaria content and increases with the conductivity. The reaction via 3PB contributes more than 60% of the total oxygen incorporated to the LSCF-Sm0.2Ce0.8O2-delta composite. (C) 2014 The Electrochemical Society. All rights reserved.