Size-Selected Cluster Deposition
and Model Catalyst Studies.
The problem: Many important catalysts consist of small clusters or nanoparticles of active metals or metal oxides, dispersed on a high surface area support (e.g. titania, alumina, silica). These catalysts are complex and difficult to study, therefore many groups have turned to planar model catalysts where catalytic clusters/nanoparticles are grown on a single crystal or thin film support, allowing them to be studied by surface science methods like STM, ion scattering, electron spectroscopies, and a variety of mass spectrometry methods. In such experiments, there is still a rather broad range of cluster/nanoparticle sizes present, as well as distributions of metal-support geometries. In our experiments, we grow catalytic cluster ions in the gas phase, then use a mass spectrometer to select a particular size/composition of interest, which is then deposited on a single crystal support to make a truly monodisperse model catalyst. We then use a variety of in situ methods to characterize morphology, electronic structure, adsorbate binding, and catalytic activity. Typical results are summarized in the PDF files linked below.
Funding AFOSR
and DOE
Recent Results: (Note: the slide shows may be too big if you
have a slow internet connection).
CO oxidation on Aun
on TiO2
CO oxidation over Pd/TiO2 - correlations of activity with
electronic structure and adsorbate binding