Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 41: Poster Session I (Semiconductor Substrates: Epitaxy and growth; Semiconductor Substrates: Adsorbtion; Semiconductor Substrates: Solid-liquid interfaces; Semiconductor Substrates: Clean surfaces; Oxides and insulators: Epitaxy and growth; Oxides and insulators: Adsorption; Oxides and insulators: Clean surfaces; Organic, polymeric and biomolecular films - also with adsorbates; Organic electronics and photovoltaics, Surface chemical reactions; Heterogeneous catalysis; Phase transitions; Particles and clusters; Surface dynamics; Surface or interface magnetism; Electron and spin dynamics; Spin-Orbit Interaction at Surfaces; Electronic structure; Nanotribology; Solid/liquid interfaces; Graphene; Others)
O 41.51: Poster
Dienstag, 23. März 2010, 18:30–21:00, Poster B1
Cluster Model Studies on Catalytic Sulfidation of MoO3 — Xue-Rong Shi1,2, Mathis Gruber2, •Klaus Hermann2, and Jianguo Wang1 — 1State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi 030001, P.R. China; — 2Fritz-Haber-Institut der MPG, Faradayweg 4-6, D-14195 Berlin and Sfb 546 "Transition Metal Oxide Aggregates", Berlin (Germany).
MoS2-based catalysts, initially prepared from MoO3, are known to yield high activity and selectivity for the production of mixed alcohols. This makes research on the sulfidation of MoO3 quite important. Here we apply density-functional theory (DFT) together with large surface clusters (cluster code StoBe) to study the sulfidation of the MoO3(010) surface as well as hydrogen adsorption at an atomic level. Surface oxygen is always found to bind more strongly with its substrate than its sulfur substitute with binding distances that are shorter for oxygen than for sulfur. Sulfur-oxygen exchange reactions are energetically preferred over sulfur adsorption at MoO3(010). Further, sulfur binding is found to be facilitated by the existence of surface oxygen vacancies where sulfur substitution takes place preferentially at the singly coordinated O(1) site. Hydrogen adsorption at the perfect and sulfidic surface leads to stable OH, H2O and SH, H2S groups which are quite weakly bound and may easily adsorb. Thus, the presence of pre-adsorbed hydrogen facilitates oxygen and sulfur removal from the MoO3(010) surface which is in qualitative agreement with earlier findings.