Adsorption and thermal reaction of short-chain alcohols on Ge(100)

Tsung Hsiang Lin, Bo Yu Lin, Ting Hao, Hsiu Yun Chien, Jeng Han Wang, Wei Hsiu Hung

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Abstract

The adsorption and thermal decomposition of alcohols (CH3OH, C2H5OH, and C4H9OH) on Ge(100) were investigated with temperature-programmed desorption and X-ray photoelectron spectra. At 105 K, CH3OH adsorbs both molecularly and dissociatively on Ge(100). Chemisorbed CH3OH molecules dissociate to form surface CH3O and hydrogen in a temperature range 150-300 K. Surface CH 3O can dehydrogenate to yield CH2O as two desorption features, which depend on coverage. At small coverage, surface CH3O undergoes mainly α-hydrogen elimination to desorb CH2O at 490 K. At large coverage, another desorption of CH2O occurs predominantly at 525 K, which is initiated by a recombinative desorption of CH3OH. A calculation with density functional theory at the B3LYP/6-311+G** level shows that the dissociation of the O-H bond has a much smaller barrier (<40 kJ/mol) than those for C-O bond cleavage (>150 kJ/mol). Desorption of CH2O results from the moderate barriers (∼110 kJ/mol) for cleavage of the C-H bond of surface CH3O and weak adsorption energy of CH2O (-56 kJ/mol). The recombination of surface CH3O with H occurs at large coverage with an energy barrier 127-140 kJ/mol. Similarly to CH3OH, C2H5OH and C4H 9OH undergo the mechanism of thermal reactions through formation of alkoxyl intermediates. The longer-chain alkoxyl decomposes to desorb aldehyde at lower temperature because the interaction of its alkoxyl chain with the surface is stronger. On annealing to ∼570 K, all alkoxyl groups are completely removed from the surface via dehydrogenation and recombination to desorb aldehyde and alcohol, respectively. At a large coverage, the longer-chain alkoxyl undergoes dehydrogenation to a larger extent than recombinative desorption.

Original languageEnglish
Pages (from-to)2760-2768
Number of pages9
JournalJournal of Physical Chemistry C
Volume117
Issue number6
DOIs
Publication statusPublished - 2013 Feb 14

Fingerprint

alcohols
Alcohols
Adsorption
desorption
adsorption
Desorption
Dehydrogenation
dehydrogenation
Aldehydes
aldehydes
Hydrogen
Energy barriers
hydrogen
Temperature programmed desorption
Photoelectrons
Hot Temperature
thermal decomposition
Density functional theory
cleavage
elimination

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

Cite this

Adsorption and thermal reaction of short-chain alcohols on Ge(100). / Lin, Tsung Hsiang; Lin, Bo Yu; Hao, Ting; Chien, Hsiu Yun; Wang, Jeng Han; Hung, Wei Hsiu.

In: Journal of Physical Chemistry C, Vol. 117, No. 6, 14.02.2013, p. 2760-2768.

Research output: Contribution to journalArticle

Lin, Tsung Hsiang ; Lin, Bo Yu ; Hao, Ting ; Chien, Hsiu Yun ; Wang, Jeng Han ; Hung, Wei Hsiu. / Adsorption and thermal reaction of short-chain alcohols on Ge(100). In: Journal of Physical Chemistry C. 2013 ; Vol. 117, No. 6. pp. 2760-2768.
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abstract = "The adsorption and thermal decomposition of alcohols (CH3OH, C2H5OH, and C4H9OH) on Ge(100) were investigated with temperature-programmed desorption and X-ray photoelectron spectra. At 105 K, CH3OH adsorbs both molecularly and dissociatively on Ge(100). Chemisorbed CH3OH molecules dissociate to form surface CH3O and hydrogen in a temperature range 150-300 K. Surface CH 3O can dehydrogenate to yield CH2O as two desorption features, which depend on coverage. At small coverage, surface CH3O undergoes mainly α-hydrogen elimination to desorb CH2O at 490 K. At large coverage, another desorption of CH2O occurs predominantly at 525 K, which is initiated by a recombinative desorption of CH3OH. A calculation with density functional theory at the B3LYP/6-311+G** level shows that the dissociation of the O-H bond has a much smaller barrier (<40 kJ/mol) than those for C-O bond cleavage (>150 kJ/mol). Desorption of CH2O results from the moderate barriers (∼110 kJ/mol) for cleavage of the C-H bond of surface CH3O and weak adsorption energy of CH2O (-56 kJ/mol). The recombination of surface CH3O with H occurs at large coverage with an energy barrier 127-140 kJ/mol. Similarly to CH3OH, C2H5OH and C4H 9OH undergo the mechanism of thermal reactions through formation of alkoxyl intermediates. The longer-chain alkoxyl decomposes to desorb aldehyde at lower temperature because the interaction of its alkoxyl chain with the surface is stronger. On annealing to ∼570 K, all alkoxyl groups are completely removed from the surface via dehydrogenation and recombination to desorb aldehyde and alcohol, respectively. At a large coverage, the longer-chain alkoxyl undergoes dehydrogenation to a larger extent than recombinative desorption.",
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AU - Lin, Tsung Hsiang

AU - Lin, Bo Yu

AU - Hao, Ting

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AU - Hung, Wei Hsiu

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AB - The adsorption and thermal decomposition of alcohols (CH3OH, C2H5OH, and C4H9OH) on Ge(100) were investigated with temperature-programmed desorption and X-ray photoelectron spectra. At 105 K, CH3OH adsorbs both molecularly and dissociatively on Ge(100). Chemisorbed CH3OH molecules dissociate to form surface CH3O and hydrogen in a temperature range 150-300 K. Surface CH 3O can dehydrogenate to yield CH2O as two desorption features, which depend on coverage. At small coverage, surface CH3O undergoes mainly α-hydrogen elimination to desorb CH2O at 490 K. At large coverage, another desorption of CH2O occurs predominantly at 525 K, which is initiated by a recombinative desorption of CH3OH. A calculation with density functional theory at the B3LYP/6-311+G** level shows that the dissociation of the O-H bond has a much smaller barrier (<40 kJ/mol) than those for C-O bond cleavage (>150 kJ/mol). Desorption of CH2O results from the moderate barriers (∼110 kJ/mol) for cleavage of the C-H bond of surface CH3O and weak adsorption energy of CH2O (-56 kJ/mol). The recombination of surface CH3O with H occurs at large coverage with an energy barrier 127-140 kJ/mol. Similarly to CH3OH, C2H5OH and C4H 9OH undergo the mechanism of thermal reactions through formation of alkoxyl intermediates. The longer-chain alkoxyl decomposes to desorb aldehyde at lower temperature because the interaction of its alkoxyl chain with the surface is stronger. On annealing to ∼570 K, all alkoxyl groups are completely removed from the surface via dehydrogenation and recombination to desorb aldehyde and alcohol, respectively. At a large coverage, the longer-chain alkoxyl undergoes dehydrogenation to a larger extent than recombinative desorption.

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