Adsorption of cyclohexadiene, cyclohexene and cyclohexane on Pt(1 1 1)

Mark Saeys, M. F. Reyniers, M. Neurock, G. B. Marin

Research output: Contribution to journalArticle

31 Scopus citations

Abstract

The adsorption of 1,3-cyclohexadiene, 1,4-cyclohexadiene, cyclohexene and cyclohexane on Pt(1 1 1) was studied using ab initio density functional theory. For 1,3-cyclohexadiene three adsorption modes were distinguished: bridge 1,2-di-σ/3,4-π, hollow 1,4-di-σ/2,3-π and bridge 1,4-di-σ/2,3-π with adsorption energies of -155, -147 and -75 kJ/mol, respectively. Three stable adsorption modes were also identified for 1,4-cyclohexadiene: bridge quadra-σ, hollow di-σ/π and bridge di-π with adsorption energies of -146 kJ/mol, -142 kJ/mol and -88 kJ/mol, respectively. Cyclohexene was found to adsorb in six modes: 4 di-σ and 2 π-adsorption modes. The preferred configuration was found to be boat di-σ with an adsorption energy of -81 kJ/mol. The three other di-σ adsorption modes have comparable adsorption energies, ranging from -64 to -69 kJ/mol. Molecular strain and C{single bond}Pt bonding energies are used to elucidate stability trends. Cyclohexane is found to adsorb only at the hollow site whereby the axial hydrogen atoms are positioned over surface Pt-atoms with an adsorption energy of -37 kJ/mol. The calculations correctly predict the weakening of the axial C{single bond}H bonds and provide a possible explanation for the large shift in the vibrational frequencies.

Original languageEnglish (US)
Pages (from-to)3121-3134
Number of pages14
JournalSurface Science
Volume600
Issue number16
DOIs
StatePublished - Aug 15 2006

Keywords

  • Catalysis
  • Chemisorption
  • Density functional calculations
  • Hydrocarbons

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