Adsorption and decomposition of ethylene and acetylene on Fe(100)

W. H. Hung, S. L. Bernasek

Research output: Contribution to journalArticle

51 Citations (Scopus)

Abstract

The adsorption of C2H4 and C2H2 on the clean, C- and O-covered Fe(100) surface was studied using HREELS, with additional information provided by TPD, AES and LEED. On the clean surface, C2H4 adsorbed molecularly on this surface in a di-σ-bonded configuration at 100 K. The di-σ-bonded C2H4 desorbed at 240 K or decomposed to form the methylidyne (CH) and ethynyl (CCH) species below 260 K. Hydrogen is the only desorption product of C2H4 decomposition. Acetylene adsorbs on the clean Fe(100) surface in a structure with hybridization of ∼ sp3. At lower exposure (< 0.2 L), C2H2 decomposes to form CH and CCH at 253 K. At higher exposure (>0.2 L), C2H2 partially dehydrogenates and hydrogenates to form CH, CCH and CHCH2 at the adsorption temperature of 100 K. When the surface is warmed to 393 K, a CCH2 species is formed by the dehydrogenation of CHCH2. The final decomposition product of ethylene is a c(2 × 2)-C surface, formed by heating the adsorbate to 523 K. A ( 1 1 -1 2)-C surface with 0.81 ML coverage is obtained by heating the acetylene adsorbed layer to 553 K. Preadsorbed carbon and oxygen block the chemisorption of di-σ-bonded C2H4 and induce physisorption of C2H4 at 100 K. Preadsorbed oxygen appears to inhibit the dehydrogenation of di-σ-bonded C2H4 and induces the adsorption of π-bonded C2H4. A carbon precovered surface shows a site-blocking effect for the adsorption of C2H2.

Original languageEnglish
Pages (from-to)272-290
Number of pages19
JournalSurface Science
Volume339
Issue number3
DOIs
Publication statusPublished - 1995 Oct 1

Keywords

  • Alkenes
  • Alkynes
  • Auger electron spectroscopy
  • Catalysis
  • Chemisorption
  • Electron energy loss spectroscopy
  • Iron
  • Low energy electron diffraction (LEED)
  • Low index single crystal surfaces
  • Physical adsorption
  • Surface chemical reaction
  • Thermal desorption
  • Thermal desorption spectroscopy

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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