Adsorption and reactions of CH2I2 on clean and oxygen-modified Ag(111): A RAIRS and TPD study

K. C. Scheer, A. Kis, J. Kiss, J. M. White

Research output: Contribution to journalArticle

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Abstract

The surface chemistry of CH2I2 on Ag(111) in the presence and absence of pre-absorbed O2, produced by NO2 adsorption at elevated temperature, was studied using TPD and reflection absorption IR spectroscopy (RAIR). CH2I2 adsorbed dissociatively at low coverage at 78K to form CH2(a) and I(a). CH2(a) groups reacted to form C2H4(g) that desorbed in a reaction-limited process during the TPD temperature ramp. As the coverage of CH2I2 was increased on the clean surface, the dissociation of the CH2I2 groups was hindered by the crowding on the surface, causing the C2H4 desorption feature to shift to higher temperatures. When CH2I2 was dosed onto Ag(111) pre-adsorbed with O(a), CH2O formed as a major reaction product. Two different states of CH2O were distinguished according to the presence of O atoms in chemisorbed and oxide-like phase. There was a minor secondary reaction route, the formation of formate, which was indicated by the desorption of CO2 groups and vibrational band in the RAIR spectra at 2810/cm.

Original languageEnglish
Pages (from-to)43-51
Number of pages9
JournalTopics in Catalysis
Volume20
Issue number1-4
DOIs
Publication statusPublished - Jul 2002

Fingerprint

Temperature programmed desorption
formic acid
Oxygen
Absorption spectroscopy
Adsorption
adsorption
Infrared spectroscopy
Desorption
oxygen
desorption
crowding
formates
ramps
Surface chemistry
Reaction products
reaction products
Temperature
Oxides
spectroscopy
routes

Keywords

  • CHI on silver
  • CHI surface chemistry
  • Oxygen-modified silver

ASJC Scopus subject areas

  • Chemistry (miscellaneous)
  • Physical and Theoretical Chemistry
  • Catalysis

Cite this

Adsorption and reactions of CH2I2 on clean and oxygen-modified Ag(111) : A RAIRS and TPD study. / Scheer, K. C.; Kis, A.; Kiss, J.; White, J. M.

In: Topics in Catalysis, Vol. 20, No. 1-4, 07.2002, p. 43-51.

Research output: Contribution to journalArticle

Scheer, K. C. ; Kis, A. ; Kiss, J. ; White, J. M. / Adsorption and reactions of CH2I2 on clean and oxygen-modified Ag(111) : A RAIRS and TPD study. In: Topics in Catalysis. 2002 ; Vol. 20, No. 1-4. pp. 43-51.
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AB - The surface chemistry of CH2I2 on Ag(111) in the presence and absence of pre-absorbed O2, produced by NO2 adsorption at elevated temperature, was studied using TPD and reflection absorption IR spectroscopy (RAIR). CH2I2 adsorbed dissociatively at low coverage at 78K to form CH2(a) and I(a). CH2(a) groups reacted to form C2H4(g) that desorbed in a reaction-limited process during the TPD temperature ramp. As the coverage of CH2I2 was increased on the clean surface, the dissociation of the CH2I2 groups was hindered by the crowding on the surface, causing the C2H4 desorption feature to shift to higher temperatures. When CH2I2 was dosed onto Ag(111) pre-adsorbed with O(a), CH2O formed as a major reaction product. Two different states of CH2O were distinguished according to the presence of O atoms in chemisorbed and oxide-like phase. There was a minor secondary reaction route, the formation of formate, which was indicated by the desorption of CO2 groups and vibrational band in the RAIR spectra at 2810/cm.

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