Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 45: Heterogeneous catalysis
O 45.8: Vortrag
Donnerstag, 26. März 2009, 12:15–12:30, SCH A215
Infrared spectroscopic studies of syngas adsorption on ZnO nanoparticles — •Heshmat Noei1, Hengshan Qiu2, Yuemin Wang1,2, Christof Wöll2, and Martin Muhler1 — 1Industrial Chemistry, Ruhr-University Bochum, 44780 Bochum, Germany — 2Physical Chemistry I, Ruhr-University Bochum, 44780 Bochum, Germany
Zinc oxide is an important material with a wide range of applications in catalysis. Presently, the most prominent application of ZnO is industrial methanol synthesis from syngas (CO2/CO/H2) over Cu/ZnO catalysts. The study of syngas adsorption on ZnO surfaces is of fundamental importance in understanding the microscopic processes occurring in methanol synthesis. In this work, the interaction of CO and CO2 with ZnO nanoparticles has been studied by ultra-high vacuum Fourier-transform infrared spectroscopy (UHV-FTIRS) together with diffuse reflectance IR spectroscopy (DRIFTS). Based on the corresponding HREELS data obtained from single-crystal surfaces, the IR results on ZnO powder samples can be understood on the atomic level. Exposing ZnO to CO2 leads to the formation of a number of carbonate species on different facets. For CO adsorption on clean ZnO powder one dominant band is observed at 2189 cm-1 and assigned to CO bound to Zn sites on ZnO(10-10). Furthermore, the FTIRS data demonstrated that the binding energy of CO is dramatically increased when ZnO is pre-modified by CO2. This unexpected effect results from the formation of tridentate carbonate species on the nonpolar (10-10) surfaces, which increase the Lewis acidity of neighboring Zn2+ cations.