| Heterogeneous catalysts consist of well dispersed mid to late transition metals supported on porous oxide powders and monoliths. Planar model supported catalysts created by vapor depositing metals on well-defined planar oxide supports in ultrahigh (UHV) are excellent tools for surface scientists to explore the factors which control the structure and reactivity of these active metal particles.; Here, we explore how adsorbed chlorine alters the structure of Cu islands supported on ZnO(0001)-Zn. Cu/ZnO are model catalysts for methanol synthesis and low temperature water gas shift reactions. With even a small amount of pre-adsorbed chlorine present, the Cu islands are thicker and cover a smaller fraction of the surface. Formate is an intermediate in methanol synthesis reactions, and decomposes on the ZnO(0001)-Zn through competing dehydrogenation and dehydration. Chlorine alters the formate decomposition reactions towards more dehydrogenation at the expense of dehydration.; Pt/ZnO are model catalysts for selective methanol dehydrogenation and hydrocarbon conversion. The structural and electronic properties of vapor-deposited Pt were studied on both the ZnO(0001)-Zn and -O surfaces. The reactivity of methanol decomposition and cyclohexane dehydrogenation was studied as a detailed function of Pt coverage on ZnO(0001)-Zn and -O, respectively. Even <0.1 ML of Pt attenuates the ability of methanol to form methoxy on Zn sites, altering the selectivity of methanol decomposition on Pt/ZnO(0001)-Zn. The reaction pathways of cyclohexane dehydrogenation changes as a function of Pt island thickness. Cyclohexane dehydrogenates completely on 2D Pt islands, which are one atomic layer thick, on the unreactive ZnO(0001)-O surface. When these Pt islands are greater than three atomic layers thick (>2 ML of Pt), H 2 TPD peaks are seen indicative of dehydrogenation of a stable benzene intermediate in cyclohexane dehydrogenation.; Cesium is a promoter in solid acid catalysts. The structural and electronic properties of Cs adsorption on TiO2(110) were also studied. Cs adsorbs cationically at low coverages, becoming more metallic at higher coverages, displaying a Stranski-Krastanov growth mode. |
