Adsorption and reaction pathways of 7-octenoic acid on copper
Adsorption and reaction pathways of 7-octenoic acid on copper
复制标题
7-辛烯酸在铜上的吸附及反应途径
DOI：
10.1039/d1cp00167a
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发表时间：
2021
影响因子：
3.3
通讯作者：
Tysoe, Wilfred T.
中科院分区：
文献类型：
--
作者：
Bavisotto, Robert;Rana, Resham;Hopper, Nicholas;Olson, Dustin;Tysoe, Wilfred T.
利用反射吸收红外光谱、X射线光电子能谱、程序升温解吸和扫描隧道显微镜相结合，并辅以第一性原理密度泛函理论计算，在超高真空中的洁净铜基底上研究了7-辛烯酸的表面结构和反应途径。 7-辛烯酸在~260 K 以下以低覆盖率的平躺结构以分子方式吸附在铜上，随着覆盖率的增加而变得更加直立。它在~300 K 吸附后去质子化形成 η2-7-辛酸物种。这在低覆盖率下也是平坦的，但随着覆盖率的增加形成更垂直的自组装单层。加热导致 7-辛烯酸酯物质开始倾斜，在~550 K 时产生少量二氧化碳，并在~615 K 处产生一些氢，归因于这些倾斜物质的反应。当 CO2 和氢气同时释放时，大部分脱羰反应发生在~650 K。大约一半的碳以低聚物形式沉积在表面，这些低聚物在~740 K 下进一步脱氢，释放出更多的氢。这会在表面留下碳质层，其中包含表示表面开始石墨化的六边形图案。
The surface structure and reaction pathways of 7-octenoic acid are studied on a clean copper substrate in ultrahigh vacuum using a combination of reflection–absorption infrared spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption and scanning-tunneling microscopy, supplemented by first-principles density functional theory calculations. 7-Octenoic acid adsorbs molecularly on copper below ∼260 K in a flat-lying configuration at low coverages, becoming more upright as the coverage increases. It deprotonates following adsorption at ∼300 K to form an η2-7-octenoate species. This also lies flat at low coverages, but forms a more vertical self-assembled monolayer as the coverage increases. Heating causes the 7-octenoate species to start to tilt, which produces a small amount of carbon dioxide at ∼550 K and some hydrogen in a peak at ∼615 K ascribed to the reaction of these tilted species. The majority of the decarbonylation occurs at ∼650 K when CO2 and hydrogen evolve simultaneously. Approximately half of the carbon is deposited on the surface as oligomeric species that undergo further dehydrogenation to evolve more hydrogen at ∼740 K. This leaves a carbonaceous layer on the surface, which contains hexagonal motifs connoting the onset of graphitization of the surface.