Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 39: Heterogeneous Catalysis

O 39.3: Poster

Dienstag, 17. März 2015, 18:15–21:00, Poster A

Zn segregation and AuZn alloy formation on Au/ZnO(0001) model catalysts in methanol synthesis gases (H₂/CO₂) — •Jan Martin, Joachim Bansmann, and R. Jürgen Behm — Institut of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm

For methanol (MeOH) synthesis, Cu/ZnO/Al₂O₃ is the main catalyst in industrial applications. Although used since the 1960s, many investigations are performed on a fundamental understanding of the reaction. It was recently found, that metallic Zn species are present in the reaction and of importance in MeOH synthesis [1]. Au/ZnO catalysts, which are currently investigated in this reaction, showed a superior selectivity compared to Cu/ZnO at comparable reactions rates.

Here, we will focus on Au/ZnO(0001) model catalysts and especially on the possible presence of metallic Zn species during MeOH synthesis. For this purpose, we monitored the development of the L₃M₄₅M₄₅ Auger peak, which is sensitive to changes in the Zn oxidation state, upon exposure to H₂/CO₂ gas mixtures (MeOH synthesis gas). Different from Cu/ZnO catalysts, where a clear relation was observed between metallic Zn species, the presence of Cu and reaction conditions, already the evaporation of Au onto ZnO(0001) under UHV conditions leads to a chemical modification of the ZnO surface. Exposure to MeOH synthesis gas (200-500mbar at 240^∘C) also affects the chemical state of the ZnO(0001) surface. Experimental results are presented for different preparations and MeOH synthesis conditions.

[1] S. Kuld et al., Angew. Chem. 126 (2014) 6051