(188a) Origin of Structure-Sensitivity of CO Oxidation on Pt/CeO2 Catalyst

CeO₂-supported Pt catalyst has been shown to be highly active for low-temperature CO oxidation. It has been shown that electron transfer between Pt and CeO₂ via electronic metal-support interaction (EMSI) is highly dependent on the size of Pt and its local coordination environment (Pt-Pt and Pt-O coordination). Therefore, CO binding on Pt and activity of Pt towards CO oxidation can be tuned by changing Pt size and its coordination environment. However, it is still not well-understood how Pt size and addition of Pt affect the properties of CeO₂, especially its ability to form and heal oxygen vacancies (O_vac) on the surface, i.e. its redox behavior. In this work, we investigate a Pt/CeO₂ system with Pt particle sizes ranging from single atoms, subnanometer clusters to 3.0 nm and probe the structural and electronic properties of Pt and CeO₂. We use multiple in situ and in operando spectroscopic techniques to show that there is a strong correlation between Pt electron density and CeO₂ O_vac concentration (or %Ce³⁺) and that this is affected by Pt particle size, i.e. Pt and CeO₂ affect the electronic properties of each other. The results show that the structure-sensitivity of CO oxidation arises from the difference in the ability of Pt to activate O₂ and the ability of CeO₂ to deliver labile and reactive O for CO oxidation. Effect of Pt particle size on both will be discussed along with the role of CeO₂ in O₂ activation. These results will be combined with CO binding energy on different Pt sizes from microcalorimetry to provide a detailed interpretation of structure-sensitivity of CO oxidation.