Interfacial and Surface Structures of CeO2−TiO2 Mixed Oxides

The interfacial and surface structures of CeO 2 −TiO 2 mixed oxides prepared by the sol−gel method have been investigated in detail by means of X-ray diffraction (XRD), BET surface area measurement, X-ray absorption spectroscopy (XAS), high-resolution transmission electron microscope (HRTEM), and selective chemisorption of methyl orange. TiO 2 and CeO 2 are in the anatase phase and the cubic fluorite phase in CeO 2 −TiO 2 mixed oxides, respectively. The mixed oxides exhibit much higher surface areas than the individual oxides and are with both mesopores and micropores. XAS results suggest that Ce atoms nucleate as cubic [CeO 8 ] polyhedrons with the formation of a Ce−O−Ti interface in mixed oxides. With the increasing Ce/TiO 2 weight ratio, the cubic fluorite CeO 2 crystallites gradually develop. TiO 2 anatase forms ultrafine particles in mixed oxides, whose local structure is stabilized by the presence of CeO 2 . HRTEM results reveal that the exposed surfaces of mixed oxides depend on the Ce concentration. Chemisorption results of methyl orange that was found to adsorb profoundly on CeO 2 but little on TiO 2 demonstrate that CeO 2 in mixed oxides exhibits much lower adsorption capacity toward methyl orange than pure CeO 2 . Our results demonstrate an approach to characterize interfacial and surface structures of complex mixed oxides, which are of great importance in understanding their properties.