Molecular beam study of oxygen and C$sub 2$ hydrocarbon chemisorption and reactions on Pt(111)
The chemisorption and reactions of oxygen and the C$sub 2$ hydrocarbons (acetylene, ethylene, and ethane) on epitaxially grown Pt(111) crystals have been studied using modulated molecular beam techniques. The sticking coefficient of ethylene is observed to be about half that for acetylene, which is near unity on oxygen covered Pt(111) in the temperature range 550--1000 K. For ethane, S<0.05 under these same conditions. The results of this study are in agreement with other studies that show that the adsorption of the C$sub 2$ hydrocarbons on platinum at elevated temperatures results in a surface acetylenic species. The first step in the oxidation process appears to be the removal of hydrogen atoms from this surface acetylene, either by molecular desorption or by reaction with surface oxygen atoms. Surface carbon then reacts with surface oxygen to form CO which either desorbs or reacts further to form CO$sub 2$. At high oxygen pressures, the reaction rate is apparently limited by the mobility of surface oxygen atoms which have an activation barrier to diffusion on Pt(111) of about 16 kcal/mole. Some implications of this high surface mobility with regard to the gas--surface oxygen equilibrium are discussed. The observance here of two distinct components in the angular desorption distributions of CO and CO$sub 2$ is discussed in terms of finer details of the reaction mechanism. (AIP)
- Research Organization:
- IRT Corporation, P.O. Box 80817, San Diego, California 92138
- NSA Number:
- NSA-33-015584
- OSTI ID:
- 4092415
- Journal Information:
- J. Vac. Sci. Technol., v. 12, no. 6, pp. 1403-1409, Other Information: Orig. Receipt Date: 30-JUN-76
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Electron
Ion & Molecular Beams & Reactions
640301* -Physics Research-Atomic
Molecular & Chemical Physics-Beams & Their Reactions
*ACETYLENE- CHEMISORPTION
*ETHANE- CHEMISORPTION
*ETHYLENE- CHEMISORPTION
*OXYGEN- CHEMISORPTION
*PLATINUM- ATOM COLLISIONS
COLLISIONS
MOLECULAR BEAMS
SURFACES