Temperature programed desorption of C{sub 2}H{sub 4} from pure and graphite-covered Pt(111)
- Physics Department, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim (Norway)
Ethylene adsorption on Pt(111) at 95 K was studied by temperature programed desorption (TPD), low energy electron diffraction (LEED), and x-ray photoelectron spectroscopy. Ethylene desorbs reversibly at 112 K and irreversibly at 255 and 280 K. It is generally accepted that annealing of ethylene adsorbed on Pt(111) to 300 K results in a dehydrogenation to ethylidyne through an ethylidene intermediate. This was observed by a hydrogen desorption peak at 300 K. Also, hydrogenation of the adsorbed ethylene was observed by a small ethane desorption peak at 300 K. Upon heating to 700 K, the ethylidyne species will further dehydrogenate to carbidic carbon species with hydrogen desorption peaks at 460 and 640 K. If the carbidic species is heated to higher temperatures (up to 1000 K), it will further dehydrogenate and form graphitic islands which will accumulate by Ostwald ripening in larger islands at the step edges of the surface. After annealing the sample to 1000 K, a statistically distributed 8x8 superstructure of these graphite islands is achieved, as interpreted from A pattern in the LEED data. The TPD results indicate that ethylene adsorption on Pt(111) results in the formation of graphitic islands upon heating to 1000 K, contrary to previous conjectures of formation of a full graphite monolayer.
- OSTI ID:
- 21020882
- Journal Information:
- Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films, Vol. 25, Issue 6; Other Information: DOI: 10.1116/1.2784721; (c) 2007 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1553-1813
- Country of Publication:
- United States
- Language:
- English
Similar Records
Coadsorption of ethylene and potassium on Pt(111). 2. Influence of potassium on the decomposition of ethylene
Reaction and chemisorption of small molecules on clean and chemically modified transition metal surfaces