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

*此作品的通信作者

研究成果: 雜誌貢獻期刊論文同行評審

7 引文 斯高帕斯(Scopus)

摘要

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.

原文英語
頁(從 - 到)2760-2768
頁數9
期刊Journal of Physical Chemistry C
117
發行號6
DOIs
出版狀態已發佈 - 2013 二月 14

ASJC Scopus subject areas

  • 電子、光磁材料
  • 能源(全部)
  • 物理與理論化學
  • 表面、塗料和薄膜

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