报告人：汪跃民 Karlsruhe Institute of Technology
Nanostructured metal oxides and oxide-supported metalshave attracted enormous attention because of their widespread applications, especially in heterogeneous catalysis and photocatalysis. The atomic arrangement on oxide surfaces and at metal-oxide interfaces determine their physical and chemical properties, and the ability to control and optimize structrual parameters is of crucial imortance. However, an atomic-scale understanding of the structure and electronic properties of many catalytic nanomaterialsis still a challenging task, which makes the fabrication and engineering of these systems largely empirical.
Here we present our recent work on ceria (CeO2), ZnO as well as TiO2-supported AuPd bimetallic nanoparticles (NPs). These systems were studied with the help of probe molecules (such as CO, O2 and N2O) and a complex ultrahigh vacuum-infrared apparatus which allows both polarization-resolved IRRAS (IR reflection-absorption spectroscopy) on model crystals and temperature-dependent IR measurements on powders. On the basis of a thorough understanding of variousceria surfaces, we gained atomic-level insights into the surface chemistry of ceria nanoparticles. Our results provided detailed information on the location of O vacancies and the relevant dioxygen activation on different surfaces.It was found that the rod-shaped ceria NPs undergo complex reconstruction and surface faceting exposing a high density of defects. The photoreactivity of ceria can be enhanced considerably by the generation of surface oxygen vacancies. In the case of ZnO, we demonstrate that the metal support plays a vital role in the structure and activity of ultrathin ZnO films. Finally, we will discuss the chemical nature of the high reactivity of TiO2-supported AuPd NPs for the CO oxidation reaction.