Surface dependence of defect sites on ceria nanocrystals probed by in situ vibrational spectroscopy

Defect sites on ceria-based catalysts have been shown to play important role in activating and converting reactants in many catalytic reactions. Ceria nanocrystals with defined surface terminations exhibit surface-dependent catalytic behaviors, but little is known about the defect sites on these differently terminated nanocrystals. In this study, in situ UV and visible Raman and infrared spectroscopy combined with probing molecules such as O₂, CO and CH₃OH are used to characterize the nature of the defect sites on ceria nanorods ({110} + {100}), nanocubes ({100}), and nano-octahedrons ({111}). It is found that both the quality and quantity of defect sites are surface-dependent on ceria nanocrystals. The differences in defect sites affect the adsorption and reactivity behaviors of the individual surfaces. The implication for catalysis will be discussed.