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O: Oberflächenphysik

O 23: Oberfl
ächenreaktionen II

O 23.9: Talk

Tuesday, March 25, 2003, 17:00–17:15, M\"UL/ELCH

HR-XPS and TPD study of the surface chemistry of acetaldehyde on Pt(111) — •R. Neubauer¹, C. Papp¹, M. Kinne¹, T. Fuhrmann¹, C. Whelan¹, M. Roth², J. Zhu¹, M. Weinelt², R. Denecke¹, and H.-P. Steinrück¹ — ¹Inst. f. Physikal. u. Theoret. Chemie, Uni Erlangen, Egerlandstr. 3, 91058 Erlangen — ²Inst. f. Angewandte Physik, Staudtstr. 7, Uni Erlangen, 91058 Erlangen

In certain industrial combustion processes acetaldehyde evolves as polluting by-product. Suitable catalysts such as Pt could lower activation energies towards decomposition and thus reduce aldehyde yields. In this framework the thermal evolution of acetaldehyde adsorbed on Pt(111) represents a model system. High-resolution XPS of the C 1s and O 1s core levels at MAX-lab and BESSY II has been applied to monitor the surface reactions in-situ. Two different types of experiments have been performed, one by applying a constant heating ramp to an adsorbed layer (TP-XPS), the other one during adsorption. As complimentary method, supporting the assignment of species, TPD measurements have also been performed. At 100 K we find at least two adsorbed species on the surface, namely physisorbed acetaldehyde and a chemisorbed acetaldehyde or acetyl species. Between 200 and 250 K the chemisorbed species converts to CH_x, CO and H. Furthermore, we find ethylidyne as possible intermediate. From recombination and decarbonylation processes, gaseous methane and CO are formed, respectively. Finally, we could exclude ketene, formaldehyde and ethane as products. Our results are compared to reported findings for a stepped Pt surface (R.W. McCabe, C.L. DiMaggio, R.J. Madix, J. Phys. Chem. 89, 854 (1985)).