In Situ Raman Observation of Oxygen Activation and Reaction at Platinum–Ceria Interfaces during CO Oxidation

Understanding the fundamental insights of oxygen activation and reaction at metal–oxide interfaces is of significant importance yet remains a major challenge due to the difficulty in in situ characterization of active oxygen species. Herein, the activation and reaction of molecular oxygen during CO oxidation at platinum–ceria interfaces has been in situ explored using surface-enhanced Raman spectroscopy (SERS) via a borrowing strategy, and different active oxygen species and their evolution during CO oxidation at platinum–ceria interfaces have been directly observed. In situ Raman spectroscopic evidence with isotopic exchange experiments demonstrate that oxygen is efficiently dissociated to chemisorbed O on Pt and lattice Ce–O species simultaneously at interfacial Ce3+ defect sites under CO oxidation, leading to a much higher activity at platinum–ceria interfaces compared to that at Pt alone. Further in situ time-resolved SERS studies and density functional theory simulations reveal a more efficient molecular pathway through the reaction between adsorbed CO and chemisorbed Pt–O species transferred from the interfaces. This work deepens the fundamental understandings on oxygen activation and CO oxidation at metal–oxide interfaces and offers a sensitive technique for the in situ characterization of oxygen species under working conditions.