CO2 Activation on Ceria: Polarization-Resolved Infrared Identification of Surface Carbonates on CeO2(110)

Abstract Understanding CO2 activation on ceria is central to elucidating elementary steps in catalytic CO2 conversion, yet direct vibrational identification of carbonate species on well-defined ceria single crystals has remained elusive. Here, we use polarization-resolved infrared reflection–absorption spectroscopy to identify surface carbonates formed upon CO2 adsorption on oxidized CeO2(110), with surface quality confirmed using CO as a probe molecule and X-ray photoelectron spectroscopy. Alongside molecularly physisorbed CO2, we observe bands at 1510 and 1280 cm–1 that we assign to a monodentate carbonate on the stoichiometric surface; their distinct polarization dependence matches the adsorption geometry predicted by density functional theory, giving direct experimental validation of the proposed structure. Additional bands at 1570 and 1610 cm–1, absent from the ideal-surface picture, are tentatively assigned to carbonates at defective sites such as step edges or oxygen vacancies. By establishing definitive, structurally validated vibrational fingerprints for CO2 activation on a single-crystal ceria surface, this work provides an essential molecular-level reference for interpreting infrared spectra of ceria-based powder catalysts.