Benzenethiol Reaction on the Clean and Hydrogen Pretreated Ni(100) Surface
Benzenethiol Reaction on the Clean and Hydrogen Pretreated Ni(100) Surface
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清洁且氢预处理的 Ni(100) 表面上的苯硫醇反应
DOI：
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
J. Gland
中科院分区：
文献类型：
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作者：
S. Kane;D. R. Huntley;J. Gland
本文研究了清洁和氢预覆盖Ni（100）表面上的苯乙烷化反应，以表征C-S键断裂。苯硫酚在90 K下以苯硫酚和表面氢的形式吸附。在270 K时，苯的主要生成途径是大覆盖度的苯乙烷. C-S键断裂涉及苯硫醇盐与镍表面的直接反应;氢似乎不直接参与。限速C-S键断裂步骤之后是吸附的苯基的快速氢化以形成从硫覆盖的表面解吸的苯。氘掺入的研究支持这种机制，因为单一的氢加成占主导地位的吸附的苯基中间体的氢化预期。对于苯乙撑饱和表面（0.30单层），氢预吸附提高苯的形成温度高达20 K，提高苯的产率高达37%。振动表征表明，在大的共吸附氢覆盖率的存在下，苯基硫醇盐的重新取向远离表面。高于500 K的脱氢吸附的苯硫醇衍生的物种的结果在形成表面结合的多环芳烃（PAH）与硫共吸附的过程中形成的氢解吸。对于低覆盖度的苯乙烷，由于更多表面的脱氢增加，没有观察到270 K的苯。在游离氢脱附温度（400 K）以上，少量的苯通过脱附形成。在镍的三个低米勒指数表面上的苯乙撑反应的比较清楚地表明，在反应温度下的氢的可用性对苯的形成有很大的影响。在Ni（100）表面上C-S键活化之前的氢脱附限制了苯的形成，而Ni（111）和Ni（110）表面上的大量氢可用性促进了苯的形成。«少
Benzenethiol reactions on clean and hydrogen precovered Ni(100) surfaces have been studied in order to characterize C-S bond breaking. Benzenethiol adsorbs at 90 K as phenylthiolate and surface hydrogen. The dominant benzene formation pathway for large coverages of benzenethiol occurs at 270 K. C-S bond breaking involves direct reaction of phenylthiolate with the nickel surface; hydrogen does not appear to be directly involved. The rate-limiting C-S bond breaking step is followed by rapid hydrogenation of adsorbed phenyl to form benzene which desorbs from the sulfur covered surface. Deuterium incorporation studies support this mechanism since single hydrogen addition dominates as expected for hydrogenation of an adsorbed phenyl intermediate. For the benzenethiol saturated surface (0.30 monolayer), hydrogen preadsorption increases the temperature of benzene formation by up to 20 K and increases the benzene yield up to 37%. Reorientation of the phenylthiolate away from the surface in the presence of large coadsorbed hydrogen coverages is indicated by vibrational characterization. Above 500 K dehydrogenation of adsorbed phenylthiolate derived species results in formation of surface bound polyaromatic hydrocarbons (PAHs) coadsorbed with sulfur; the hydrogen formed in the process desorbs. For low coverages of benzenethiol, no 270 K benzene is observed due to increased dehydrogenation bymore » the surface. A small amount of benzene is formed by disproportionation above the temperature of free hydrogen desorption (400 K). A comparison of benzenethiol reactions on the three low Miller index surfaces of nickel clearly indicates that hydrogen availability at reaction temperature has a large influence on benzene formation. Hydrogen desorption prior to C-S bond activation on the Ni(100) surface limits benzene formation, while substantial hydrogen availability on the Ni(111) and Ni(110) surfaces facilitates benzene formation.« less