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

Research output: Contribution to journalArticle

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Abstract

The adsorption and thermal decomposition of alcohols (CH 3 OH, C 2 H 5 OH, and C 4 H 9 OH) on Ge(100) were investigated with temperature-programmed desorption and X-ray photoelectron spectra. At 105 K, CH 3 OH adsorbs both molecularly and dissociatively on Ge(100). Chemisorbed CH 3 OH molecules dissociate to form surface CH 3 O and hydrogen in a temperature range 150-300 K. Surface CH 3 O can dehydrogenate to yield CH 2 O as two desorption features, which depend on coverage. At small coverage, surface CH 3 O undergoes mainly α-hydrogen elimination to desorb CH 2 O at 490 K. At large coverage, another desorption of CH 2 O occurs predominantly at 525 K, which is initiated by a recombinative desorption of CH 3 OH. 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 CH 2 O results from the moderate barriers (∼110 kJ/mol) for cleavage of the C-H bond of surface CH 3 O and weak adsorption energy of CH 2 O (-56 kJ/mol). The recombination of surface CH 3 O with H occurs at large coverage with an energy barrier 127-140 kJ/mol. Similarly to CH 3 OH, C 2 H 5 OH and C 4 H 9 OH 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
methylidyne
Adsorption
adsorption
Desorption
desorption
Dehydrogenation
Aldehydes
Hydrogen
Energy barriers
Temperature programmed desorption
Photoelectrons
Hot Temperature
dehydrogenation
aldehydes
Density functional theory
Pyrolysis
Annealing
X rays

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 (CH 3 OH, C 2 H 5 OH, and C 4 H 9 OH) on Ge(100) were investigated with temperature-programmed desorption and X-ray photoelectron spectra. At 105 K, CH 3 OH adsorbs both molecularly and dissociatively on Ge(100). Chemisorbed CH 3 OH molecules dissociate to form surface CH 3 O and hydrogen in a temperature range 150-300 K. Surface CH 3 O can dehydrogenate to yield CH 2 O as two desorption features, which depend on coverage. At small coverage, surface CH 3 O undergoes mainly α-hydrogen elimination to desorb CH 2 O at 490 K. At large coverage, another desorption of CH 2 O occurs predominantly at 525 K, which is initiated by a recombinative desorption of CH 3 OH. 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 CH 2 O results from the moderate barriers (∼110 kJ/mol) for cleavage of the C-H bond of surface CH 3 O and weak adsorption energy of CH 2 O (-56 kJ/mol). The recombination of surface CH 3 O with H occurs at large coverage with an energy barrier 127-140 kJ/mol. Similarly to CH 3 OH, C 2 H 5 OH and C 4 H 9 OH 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

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AU - Wang, Jeng-Han

AU - Hung, Wei-Hsiu

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AB - The adsorption and thermal decomposition of alcohols (CH 3 OH, C 2 H 5 OH, and C 4 H 9 OH) on Ge(100) were investigated with temperature-programmed desorption and X-ray photoelectron spectra. At 105 K, CH 3 OH adsorbs both molecularly and dissociatively on Ge(100). Chemisorbed CH 3 OH molecules dissociate to form surface CH 3 O and hydrogen in a temperature range 150-300 K. Surface CH 3 O can dehydrogenate to yield CH 2 O as two desorption features, which depend on coverage. At small coverage, surface CH 3 O undergoes mainly α-hydrogen elimination to desorb CH 2 O at 490 K. At large coverage, another desorption of CH 2 O occurs predominantly at 525 K, which is initiated by a recombinative desorption of CH 3 OH. 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 CH 2 O results from the moderate barriers (∼110 kJ/mol) for cleavage of the C-H bond of surface CH 3 O and weak adsorption energy of CH 2 O (-56 kJ/mol). The recombination of surface CH 3 O with H occurs at large coverage with an energy barrier 127-140 kJ/mol. Similarly to CH 3 OH, C 2 H 5 OH and C 4 H 9 OH 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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