MORPHOLOGY, STRUCTURE, DEFECTS AND REACTIVITY OF OXIDE SURFACES AND SUPPORTED METAL NANOPARTICLES
WG1 members: Clemens Barth, Philippe Parent, Carine Laffon
homepage: Reactivity and structure analysis, Theory
Scientists involved in the COST action CM1104 at the CINaM institute deal with the morphological, atomic and electronic structure of different oxide surfaces and supported metal nanoparticles, with a strong link to heterogeneous model catalysis. In particular, thin films of magnesium oxide, alumina and ceria are of interest, whereas nanometer sized Au, Pt, Pd, Ag, Au and even bi-metallic nanoparticles are relevant. Reducibility plays a fundamental role in all considered studies, in particular with respect to ceria.
Current research within the COST action
Noncontact Atomic Force Microscopy (nc-AFM), Kelvin Probe Force Microscopy (KPFM) and X-ray Photo-Electron Spectroscopy are currently used to study oxide surfaces and supported metal nanoparticles. The following equipments are used:
- One room temperature Omicron UHV nc-AFM/STM (C. Barth)
- One room temperature PSP Resolve 120 Photo-Electron Spectrometer (Ph. Parent, C. Laffon)
In principle, High-Resolution Transmission Electron Microscopy (HR-TEM) under environmental conditions (E-TEM) and a low temperature AFM/STM based on the QPlus sensor are available (contact: C. Barth).
At the moment, the morphology and electronic structure of thick ceria films are studied by nc-AFM/KPFM (C. Barth) and XPS (Ph. Parent, C. Laffon), in collaboration with the group of M. Reichling from the University of Osnabrück. We study the influence of the UHV annealing and the annealing in oxygen on the stoichiometry of the ceria films (reduction via UHV annealing (e.g. to Ce2O3), oxidation via annealing in oxygen (e.g. to CeO2)). The goal is to find best parameters for the preparation of almost atomically flat and well-defined ceria surfaces (flatness, stoichiometry, etc.). Well-defined surfaces are then used to study the properties of oxygen vacancies and their influence on supported metal nanoparticles.