ARTICLE pubs.acs.org/Langmuir
Computational Investigation of O2 Reduction and Diffusion on 25% Sr-Doped LaMnO3 Cathodes in Solid Oxide Fuel Cells Hsin-Tsung Chen,*,† P. Raghunath,‡ and M. C. Lin*,‡ † ‡
Department of Chemistry, Chung Yuan Christian University, Chungli 32023, Taiwan Department of Applied Chemistry and Institute of Molecular Science, National Chiao Tung University, Hsinchu 30010, Taiwan
bS Supporting Information ABSTRACT: The oxygen reduction reaction (ORR) and diffusion mechanisms on 25% Sr-doped LaMnO3 (LSM) cathode materials as well as their kinetic behavior have been studied by using spin-polarized density functional theory (DFT) calculations. Bader charge and frequency analyses were carried out to identify the oxidation state of adsorbed oxygen species. DFT and molecular dynamics (MD) results show that the fast O2 adsorption/reduction process via superoxide and peroxide intermediates is energetically favorable on the Mn site rather than on the Sr site. Furthermore, the higher adsorption energies on the Mn site of the (110) surface compared to those on the (100) surface imply that the former is more efficient for O2 reduction. Significantly, we predict that oxygen vacancies enhance O2 reduction kinetics and that the O-ion migration through the bulk is dominant over that on the surface of the LSM cathode.
’ INTRODUCTION The need for low-cost, clean, efficient future energy has stimulated a great amount of interest in the development of alternative energy sources. Solid oxide fuel cells (SOFCs) have been considered to be one potential possibility for future power generation because of their high energy efficiency and good fuel flexibility. However, one of the critical scientific challenges in fuel cell applications is the development of reliable, low-cost SOFCs.1 This requirement may be achieved by reducing the operating temperature, which, however, results in cathodic polarization and increases in resistance, where oxygen reduction represents a significant internal loss at low temperatures (
