| Pt/gamma-Al2O3 is arguably the most important heterogeneous catalyst system, as it is used in numerous technologically important processes, including oil refining, catalytic converters and fuel cells. Hence, many investigators have studied Pt/gamma-Al2O3 both experimentally and theoretically. Yet, a significant gap exists between experiment and theory since theory models well defined finite systems whereas the commercially available gamma-Al2O3 is polycrystalline with ill-defined morphologies, crystallography and impurities. The goal of this thesis project is to synthesize a model Pt/gamma-Al2O3 heterogeneous catalyst system which is in the appropriate size regime for theoretical modeling. The critical challenge of this project is the creation of single crystal gamma-Al 2O3 thin films. To achieve this goal, the growth of single crystal gamma-Al2O3 thin film on NiAl(110) surface was systematically investigated by oxidation in dry ambient air to determine the optimal oxidation parameters to form a reasonably flat, defect-free, single crystal gamma-Al2O3 film. We determined that the optimal oxidation condition was 850°C for 1 hour in air that produced an 80 nm thick film with an RMS value of 10 nm. The model Pt/gamma-Al2O 3 system was produced by e-beam evaporation of Pt nanoparticles onto the surface of the gamma-Al2O3. We characterized the Pt/gamma-Al2O3 by transmission electron microscopy techniques for morphological and electronic structure of the nanoparticles and interfaces, respectively. We provide two feasibility studies of obtaining benchmark parameters that could be used by theorists: (1) the interfacial energy through a Wulff-Kashiew analysis of the supported Pt nanoparticles' shapes and (2) information on the density of states at the interface using electron energy loss spectroscopy. During the course of this study, we also discovered aspects of NiAl oxidation kinetics in the intermediate temperature regime of 650-950°C where only gammagamma-Al2O3 forms, not the thermodynamically stable alpha-Al2O3. For example, crystallinity, epitaxy, and surface roughness of the oxide depends on the oxidation temperature due to temperature-dependent strain and relative diffusion behaviors. |
