Abstract

A one-dimensional continuum model related to close-packing theory has been developed to produce insights into the oxygen reduction reaction (ORR) process in a dense LSM-type cathode system. By incorporating SOFC cathode particle size, the modeling simulations reveal detailed surface processes and parallel reaction pathways responding to polarization-induced changes. A formula to distinguish the contributions of surface diffusion and local reactions to total 3PB is presented, which allows an estimation of the detailed influencing factor for 3PB/2PB transition. The results reveal that the essential correspondence in spatial domains of surface adsorbates and oxygen vacancies implies tight coupling behavior for 3PB/2PB kinetic competition. The kinetic domination of surface reactions shifts between oxygen adsorption and incorporation, demonstrates the importance of harmonization between surface activity and ionic conduction for improving the overall electrochemical performance of SOFC cathode. Such mechanistic studies suggest means of rational design of more active cathodes to optimize the overall electrochemical performance.

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