甲醇與雙官能基分子在Ge(100)表面上的吸附與熱分解反應

Adsorption and Thermal Reactions of Methanol and Bifunctional Molecules on Ge(100)

林琮翔(Tsung-Hsiang Lin)

指導教授 ： 洪偉修

國立臺灣師範大學/理學院/化學系/碩士(2011年)

摘要

利用程溫脫附質譜儀 (TPD) 及X光光電子能譜 (XPS) 來研究甲醇 (CH3OH) 與雙官能基分子 (1,2-乙二硫醇、2-巰基乙醇及1,2-乙二醇) 在Ge(100)表面上的吸附與熱分解反應。
在100 K時，甲醇曝露到Ge (100)表面，部分分子會斷氧氫鍵形成表面甲基氧與表面氫，而其餘分子則以甲醇分子吸附在表面上。而甲醇在鍺表面上的熱分解產物為H2、HCHO及CH3OH。當溫度升至300 K時，表面上的甲醇分子會有兩個競爭反應，一是直接從表面上脫附，另一則是斷氧氫鍵形成表面甲基氧與表面氫。當曝露量低時，表面甲基氧在470 K會藉由氫裂解形成甲醛，隨著升溫進而脫附；而曝露量較高時，表面甲基氧在530 K時會有兩個競爭反應，一部分與表面氫再結合形成甲醇分子脫附，另一部分則是經由氫裂解形成甲醛脫附。
為了比較醇與硫醇官能基的差異，我們選擇具有雙官能基分子 (1,2-乙二硫醇、2-巰基乙醇及1,2-乙二醇) 來研究。其中，1,2-乙二硫醇及2-巰基乙醇在高溫時皆會藉由斷裂碳氧鍵或碳硫鍵進而產生乙烯，2-巰基乙醇則有部分碳氧鍵未斷形成乙醛；相較之下1,2-乙二醇則是以相似於甲醇的方式進行氫裂解形成乙雙醛。此篇論文是針對上述化合物在Ge (100)表面的反應機制加以探討。

關鍵字

鍺 ； 甲醇 ； 1,2-乙二硫醇 ； 2-巰基乙醇 ； 1,2-乙二醇

並列摘要

The adsorptions and thermal reactions of methanol (CH3OH) and bifunctional molecules (HSC2H4SH, HSC2H4OH, and HOC2H4OH) on Ge(100) surface were investigated with temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). The desorption products of thermal reactions could be measured by TPD, and the XPS was ulitized to identify the surface species.
Adsorption of methanol on Ge(100) at 100 K results in the partial methanol forming surface OCH3 and surface H, other methanol directly adsorb on the surface. The desorption products of thermal decomposition were H2, HCHO, and CH3OH. The methanol molecules proceed two competitive reactions : the methanol directly desorbs from the surface , and forms surface OCH3 and surface H via the breaking of O-H bond. When low coverage, formaldehyde is produced due to the hydrogen elimination of surface OCH3 at 470 K, and desorbs with the increasing of temperature. While the coverage is high, the formation of formaldehyde via the hydrogen elimination competes with the formation of methanol due to the recombination of surface OCH3 and H at 530 K.
In order to compare the two functional groups (OH and SH) , we investigate the ethane molecule of bifunctional groups, 1,2-ethanedithiol, 2-mercaptoethanol, and 1,2-ethanediol. The thermal reactions of 1,2-ethanedithiol and 2-mercaptoethanol produce ethene via the breaking of C-S and C-O bonds respectively. While the minor 2-mercaptoethanol does not break C-O bond, and form acetaldehyde. In contrast, the thermal reaction of 1,2-ethanediol produces ethanedial via the hydrogen elimination similar to the case of methanol. The thermal reaction mechanisms of the above compounds on Ge(100) are studied and discussed in this dissertation.

並列關鍵字

Ge ； methanol ； 1,2-ethanedithiol ； 2-mercaptoethanol ； 1,2-ethanediol

參考文獻

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