Nickel Deposition on ?-Al2O3: Modelling Metal Particle Behaviour at the Support

Recently, surface modifications on a commercial Ni/Al2O3 catalyst during the production of methane from synthesis gas were investigated by quasi in situ X-ray photoelectron spectroscopy (XPS). The effect of the synthesis gas on the surface properties of the catalyst and on its activity under methanation conditions was studied on an atomic level. The conclusion was that the stability of Ni particles on the ?-Al2O3 support can be influencedby cluster growth phenomena, which influence both size and distribution of the metal particles. In this study, Ni deposition and cluster growth on model catalyst samples (10 nm thick, polycrystalline ?-Al2O3 on Si(100)) was investigated by XPS. The molecular structure of the catalyst was investigated using Density Functional Theory calculations (StoBe) with cluster model and non-local functional (RPBE) approach. Al15O40H35 clusterswere selected to represent the ?-Al2O3 (100) surface. Ni clusters of different size were cut from a Ni(100) surface and deposited on the Al15O40H35 cluster in order to validate the deposition model determined by XPS.