Nature and Reactivity of Oxygen Species on/in Silver Catalysts during Ethylene Oxidation

The nature of surface oxygen species on/in a silver powder catalystand their reactivity with ethylene were systematically investigated with multiplespectroscopies and DFT calculations. Unique quasiin situHS-LEIS,in situNAP-XPS, andin situRaman spectroscopy demonstrated that the silver surface iscovered by a thin oxide layer (1-3 nm) after an oxidation treatment and duringethylene oxidation. Periodic DFT models allowed assignments of oxygen speciesdetected byin situRaman spectroscopy with detailed structures on p(4x4)-O-Ag(111) surfaces.In situNAP-XPS and Raman spectroscopy suggest that Ag4-O2on oxidized Ag is the active oxygen species for ethylene epoxidation. Theexperimental and theoretical methodologies developed in the present work serve asan efficient toolbox for the scientific investigation of the silver-oxygen system forselective oxidation reactions and rational guidance of computational calculationscoupled with experimentalfindings.