Surface Transport Mechanism and Bi-Pathway ORR Kinetics for Solid Oxide Fuel Cell Cathode

The oxygen reduction reaction (ORR) taking place at the cathode plays a very prominent role in the electrochemical performance and operating efficiency of SOFCs. In this study, the major drive in undertaking modeling simulation of ORR kinetics is to provide useful insight into a fundamental understanding of the detailed surface contribution and parallel ORR kinetics of LSM-type cathodes under different polarization conditions. A continuum method in dense electrode systems combined with a microscopic approach is used to establish the relationship among particle size, polarization properties, and ORR behavior of the SOFC cathode. Here, we employ dense electrodes with a face centered cubic lattice (fcc) structure owing to the complex morphology and structure of porous/composite electrodes. For using bigger particles (e.g.1.0μm), the active reaction zone is extended due to the distribution of absolutely higher concentration of oxygen vacancy. However, mass-transport limitation of adsorbates is responsible for smaller flux value of bulk oxygen vacancy, resulting in slower 2PB kinetics behavior. The results indicate that small fluctuations in the electrode particle size produce a measurable impact in electrode performance, which should be considered in operational performance models.