ADSORPTION AND SURFACE STRUCTURAL CHEMISTRY OF THIOPHENOL, BENZYL MERCAPTAN, AND ALKYL MERCAPTANS - COMPARATIVE-STUDIES AT AG(111) AND PT(111) ELECTRODES BY MEANS OF AUGER-SPECTROSCOPY, ELECTRON-ENERGY LOSS SPECTROSCOPY, LOW-ENERGY ELECTRON-DIFFRACTION, AND ELECTROCHEMISTRY
ADSORPTION AND SURFACE STRUCTURAL CHEMISTRY OF THIOPHENOL, BENZYL MERCAPTAN, AND ALKYL MERCAPTANS - COMPARATIVE-STUDIES AT AG(111) AND PT(111) ELECTRODES BY MEANS OF AUGER-SPECTROSCOPY, ELECTRON-ENERGY LOSS SPECTROSCOPY, LOW-ENERGY ELECTRON-DIFFRACTION, AND ELECTROCHEMISTRY
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DOI：
10.1021/la00053a024
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发表时间：
1991-05-01
期刊：
影响因子：
3.9
通讯作者：
HUBBARD, AT
中科院分区：
文献类型：
--
作者：
GUI, JY;STERN, DA;HUBBARD, AT
报道了一系列有机硫化合物的表面电化学研究，比较了它们在水溶液中在Ag（111）和Pt（111）电极表面的行为。 利用俄歇能谱研究了分子的堆积密度和化学计量比。 用电子能量损失谱（EELS）表面振动谱表征了分子结构和表面化学键。 用低能电子衍射（LEED）研究了表面的长程有序性。 利用伏安法研究了表面电化学行为。 所研究的化合物代表各种类型的芳族硫醇和烷基硫醇：苯硫酚（TP）;苄基硫醇（BM）; 1-丙硫醇（PT）; 2-巯基乙醇（ME）; 2-氨基乙硫醇（AET）;和2-巯基乙磺酸钠盐（MES）。 还研究了吡啶和两种在Pt（111）电极上化学吸附但不在Ag（111）上化学吸附的其他衍生物：吡啶（PYR）;吡啶-d5（PYR-D5）;和（3-吡啶基）氢醌（3 PHQ）。 结果表明，硫醇和硫醇主要通过硫原子连接到Pt（111）和Ag（111）表面，而分子的其余部分作为侧基存在。 巯基氢的溶解伴随着吸附。 通过俄歇光谱在Pt（111）和Ag（111）表面测量的分子堆积密度是相似的，并且与基于分子模型的理论极限堆积密度非常一致。 这些吸附物显然保留其框架分子结构在吸附状态的基础上的EELS光谱的每个吸附物和未吸附的化合物的IR光谱之间的密切相似性。 硫醇和硫醇在Ag（111）处比在Pt（111）处显示出更大的形成具有长程有序的单分子膜的趋势，如LEED所判断的。 例如，TP、BM和MES在Ag（111）处形成相称结构，但在Pt（111）：Ag（111）处不产生LEED图案。（无根7 x无根31，88度）R40.9度，TP; Ag（111）（2个无顶自由基3x 2个无顶自由基3）R30-度，BM;和Ag（111）（3个无顶自由基3，90-度）R30-度，MES。 PT，ME和AET的吸附层在两个表面上都是无序的。
Surface electrochemical studies are reported for a series of organic sulfur compounds, comparing their behavior at Ag(111) and Pt(111) electrode surfaces in aqueous solutions. Molecular packing density and stoichiometry were investigated by use of Auger spectroscopy. Molecular constitution and surface chemical bonding were characterized by electron energy loss spectroscopy (EELS) surface vibrational spectroscopy. Surface long-range order was examined by low-energy electron diffraction (LEED). Surface electrochemical behavior was explored by use of voltammetric methods. Compounds studied represent various types of aromatic thiols and alkyl mercaptans: thiophenol (TP); benzyl mercaptan (BM); 1-propanethiol (PT); 2-mercaptoethanol (ME); 2-aminoethanethiol (AET); and 2-mercaptoethanesulfonic acid sodium salt (MES). Also studied were pyridine and two other derivatives which chemisorb at Pt(111) electrodes but not at Ag(111): pyridine (PYR); pyridine-d5 (PYR-D5); and (3-pyridyl)hydroquinone (3PHQ). The results indicate that thiols and mercaptans are attached to the Pt(111) and Ag(111) surface primarily through the sulfur atom with the remainder of the molecule being present as a pendant. Dissolution of the sulfhydryl hydrogen accompanies adsorption. Molecular packing densities measured by means of Auger spectroscopy at Pt(111) and Ag(111) surfaces are similar and are in close agreement with theoretical limiting packing densities based upon molecular models. These adsorbates evidently retain their framework molecular structure in the adsorbed state based upon the close similarity between the EELS spectrum of each adsorbate and the IR spectrum of the unadsorbed compound. Thiols and mercaptans show a greater tendency to form monolayers having long-range order at Ag(111) than at Pt(111), as judged by LEED. For example, TP, BM, and MES form commensurate structures at Ag(111) but do not yield LEED patterns at Pt(111): Ag(111)(unroofed-radical 7 x unroofed-radical 31, 88-degrees) R40.9-degrees, TP; Ag(111)(2 unroofed-radical 3x2 unroofed-radical 3) R30-degrees, BM; and Ag(111) (3 x unroofed-radical 3, 90-degrees) R30-degrees, MES. Adsorbed layers of PT, ME, and AET were disordered at both surfaces.