Vibrational Spectroscopy of Acetylene Decomposition on Palladium (111) and (100) Surfaces.
Interim technical rept.,
INDIANA UNIV AT BLOOMINGTON DEPT OF PHYSICS
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Vibrational spectra for thermal decomposition of acetylene C2H2 on 111 and 100 surfaces of palladium obtained with high-resolution electron energy loss spectroscopy EELS are described. Of particular interest is the formation of CCH species on both surfaces, which are identified spectroscopically in this context for the first time. On Pd100 CCH forms with thermal processing of chemisorbed acetylene to approximately 400K but on Pd111 is co-adsorbed with a triple bond C-CH3 species following 300K C2H2 adsorption. With further annealing to 450K CCH is the dominant species on both surfaces. The EELS spectra indicate that both carbon atoms are involved in the CCH interaction with the surface as implied by a C-C bond order between 1 and 2. In view of recent reports of acetylene trimerization to benzene C6H6 on Pd surfaces the EELS spectra of C6H6 and isotopic mixtures were also analyzed but no evidence of this reaction was found.
- Organic Chemistry
- Atomic and Molecular Physics and Spectroscopy