Laterally-structured model catalysts via functionalization of mesoscopically-structure surfaces of oxides
Using well-defined micro- and nanostructured model catalyst systems, we plan to investigate (i) size effects and particle shapes of catalytically-active nanoparticles and (ii) their interaction with the substrate with respect to their catalytic function as well as (iii) details of transport and spill-over processes of the catalytic reactions. The model systems will mainly consist of Au nanoparticles on planar metal oxide substrates created via the micellar-based technique. This technique allows to produce nearly monodispersed Au nanoparticles using appropriate polymer shells and Au loadings. Moreover, these nanoparticles are quasi laterally ordered on atomically flat metal oxide substrates with a narrow distribution of the inter particle distances and the size and the inter particle distances can be tuned separately before deposition. These structurally well-defined model systems allow us to investigate locally the chemical/catalytic properties as well as local transport processes.
In this project, the investigations focus on a detailed understanding of the following objectives:
(i) the interaction between Au nanoparticles and oxidic substrate, especially on the structure of the Au-TiO2 interface and the shape of the nanoparticles (depending on different preparation conditions and the size of the Au particles) in correlation with the chemical reactivity;
(ii) the influence of additional metal components in bimetallic nanoparticles on these properties, and
(iii) the influence of transport phenomena and spill-over processes on the reactivity.
In order to reach these goals, we will use new methods that are either sensitive on the structure of individual particles or an ensemble of particles, such as high resolution TEM and in-situ X-ray scattering (under reaction atmospheres) or in-situ spectroscopic methods such as high-pressure XPS or IR. These investigations will be supported by a close cooperation with theory (A8). A variation of the inter-particle distance with respect to the reactivity allows to obtain information about spill-over processes. Finally, we will investigate mesoscopic transport effects in the CO oxidation on micro-structured Au/TiO2 surfaces with Au-functionalized fields and inert areas in between (in the 10-100 µm regime) using a scanning mass spectrometer.