Structure and special chemical reactivity of interface-stabilized cerium oxide nanolayers on TiO2(110)

Abstract

Novel interface-stabilized ceria nanophases have been grown on TiO₂(110) by physical vapor deposition. At low coverage, dumbbell nanostructures constituted by reconstructed titania and ceria clusters are formed, while long range ordered nanoxides can be obtained by increasing the ceria dose. Scanning tunneling microscopy and photoemission spectroscopy were used to characterize the electronic properties of the films, showing that the TiO₂ substrate can effectively stabilize ceria in reduced form over a wide range of experimental conditions. Epitaxial coupling is a very useful tool for tuning the chemical properties of mixed oxide systems. The special electronic properties of the films have a direct counterpart in the chemical activity, which has been investigated by temperature programmed desorption using methanol as a probe molecule. The experimental results indicate an exceptional activity of the ceria–titania interface in the selective dehydration of methanol to formaldehyde at an unprecedented low temperature (330 K).