Role of Interfacial Cu-Ions in Polycrystalline Cu-CeO₂: In-Situ Raman, In-situ DRIFT and DFT Studies for Preferential Oxidation of CO in Presence of Excess H₂**

In this work, we designed a polycrystalline Cu-CeO₂ catalyst with defect sites, and it has superior CO oxidation activity in presence of excess H₂. The oxygen defects of Cu-CeO₂ influence the adsorption of unalike surface di-oxygen types, and the catalyst was characterized through XRD (X-Ray Diffraction) analysis, TEM (Transmission electron microscopy), in-situ Raman spectroscopy, in-situ DRIFT (Diffuse reflectance infrared fourier transform) spectroscopy. TEM showed that CeO₂(111) plane are the exposed plane for this reaction. Raman spectroscopy showed nature of the defects of the prepared catalyst and how it works in the reaction environment. In-situ DRIFT spectroscopy showed that the Cu⁺↔Cu²⁺ system is working in this reaction environment. Role of interfacial Cu ions was confirmed by in-situ DRIFT spectroscopy and DFT (Density functional theory) study.