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CO Oxidation Mechanism on CeO2-Supported Au Nanoparticles

Kim, Hyun You, Lee, Hyuck Mo, Henkelman, Graeme
Journal of the American Chemical Society 2012 v.134 no.3 pp. 1560-1570
carbon monoxide, catalysts, catalytic activity, ceric oxide, energy, gold, metal ions, nanogold, oxidation, oxygen, superoxide anion
Density functional theory was used to study the CO oxidation catalytic activity of CeO₂-supported Au nanoparticles (NPs). Experimental observations on CeO₂ show that the surface of CeO₂ is enriched with oxygen vacancies. We compare CO oxidation by a Au₁₃ NP supported on stoichiometric CeO₂ (Au₁₃@CeO₂-STO) and partially reduced CeO₂ with three vacancies (Au₁₃@CeO₂-3VAC). The structure of the Au₁₃ NP was chosen to minimize structural rearrangement during CO oxidation. We suggest three CO oxidation mechanisms by Au₁₃@CeO₂: CO oxidation by coadsorbed O₂, CO oxidation by a lattice oxygen in CeO₂, and CO oxidation by O₂ bound to a Au–Ce³⁺ anchoring site. Oxygen vacancies are shown to open a new CO oxidation pathway by O₂ bound to a Au–Ce³⁺ anchoring site. Our results provide a design strategy for CO oxidation on supported Au catalysts. We suggest lowering the vacancy formation energy of the supporting oxide, and using an easily reducible oxide to increase the concentration of reduced metal ions, which act as anchoring sites for O₂ molecules.