Adsorption and Reactions of CH2I2 on Clean and Oxygen-Modified Ag(111): a RAIRS and TPD Study |
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| Authors: | Scheer K.C. Kis A. Kiss J. White J.M. |
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| Affiliation: | (1) Center for Materials Chemistry, Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712, USA;(2) Reaction Kinetics Research Group of Hungarian Academy of Sciences, University of Szeged, Szeged, Hungary;(3) Center for Materials Chemistry, Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712, USA |
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| Abstract: | The surface chemistry of CH2I2 on Ag(111) in the presence and absence of pre-adsorbed O, produced by NO2 adsorption at elevated temperature, has been examined using temperature-programmed desorption and reflection absorption infrared spectroscopy. There is good evidence for the formation of adsorbed methylene, CH2(a), that reacts with another CH2(a) to form and desorb ethylene, C2H4(g), in a reaction-limited process. Increasing the surface coverage of CH2I2 hinders both the dissociation and recombination processes indicated by the upward temperature shift in the formation of C2H4. Co-adsorbed O atoms strengthen the bonding of CH2I2 to the surface; the increased thermal stability is up to 60 K. The formation of C2H4 decreases with increasing amounts of pre-adsorbed O; the main reaction product is CH2O produced in a reaction-limited process. CH2O forms either on the chemisorbed or on the oxide phase with desorption peak temperatures of 225 and 270 K, respectively. The formation of gas-phase carbon dioxide suggests that a formate intermediate is involved in a secondary reaction pathway. |
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| Keywords: | CH2I2 surface chemistry CH2I2 on silver oxygen-modified silver |
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