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1.
本文应用第一性原理的密度泛函(DFT)方法,使用DMol3计算程序,对NO在Rh(100)和Rh(111)面上的吸附与分解进行量化计算,力图解决NO在Rh(100)和Rh(111)面上的优选吸附位、直接分解的过渡态和活化能等重要问题. 相似文献
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The adsorption of carbon monoxide on single-crystal transition metal surfaces has been the subject of numerous studies, because it has served as a model system for the adsorption of small molecules on transition metal surfaces, and its industrial importance is obvious in such areas as catalytic reaction. The bonding of carbon monoxide to rhodium is of special interest since this metal catalyzes the hydrogenation of CO to produce hydrocarbons in both heterogeneous and homogeneous media, and it … 相似文献
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吡啶作为加氢脱氮的模型化合物,与过渡金属Pt(111),Ni(100),Pd(110,111),Mo(110),Rh(111)面的吸附作用已有大量的实验研究,所采用的技术基本上是LEED,TDS,XPS,HREELS等,然而吡啶与Rh(111)面作用的理论研究尚未见报道.本文用EHMO法研究了吡啶与Rh(111)面的吸附作用,得到了最优吸附构型、结合能、集居数以及电荷分布和转移等,为新的脱氮催化剂开发提供了理论依据. 计算采用EHMO法,其中非对角矩阵元采用MWH近似: 相似文献
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在Rh(111)面上NO+CO反应机理的密度泛函理论研究 总被引:1,自引:0,他引:1
应用基于密度泛函理论赝势平面波方法的CASTEP程序, 对Rh(111)上的NO+CO反应机理进行研究. 对于反应中的各个关键步骤: NO离解、CO2生成、通过N2O离解生成N2以及通过N+N反应生成N2都进行了详细讨论, 计算得到各反应步骤的过渡态以及活化能, 从而确立了各步骤的反应路径. 相似文献
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采用密度泛函理论(DFT)的B3LYP方法,以原子簇Rh13(9,4)为模拟表面,在6-31G(d,p)与Lanl2dz基组水平上,对甲氧基在Rh(111)表面的四种吸附位置(fcc、hcp、top、bridge)的吸附模型进行了几何优化、能量计算、Mulliken电荷布局分析以及前线轨道的计算。结果表明,当甲氧基通过氧与金属表面相互作用时,在bridge位的吸附能最大,吸附体系最稳定,在top位转移的电子数最多;吸附于Rh(111)面的过程中C—O键被活化,C—O键的振动频率发生红移。 相似文献
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<正>Adsorption behaviors of 2-bromothiophene on the Rh(111)surface were discussed with DFT.The results revealed that adsorption at the parallel hol site and bridge site was the most stable.After adsorption,bond length of 2-bromothiophene changed significantly.Molecular plane was distorted,and C-H(Br,S)in the molecule was oblique and upswept against the metal surface.Vertical adsorption site was less stable than the plane adsorption site,but there was no distortion for the thiophene ring after adsorption.Aromaticity of 2-bromothiophene was destroyed at the hol and bridge adsorption sites,and the carbon atom in the thiophene ring presented quasi-sp~3 hybridization.After adsorption at the parallel hol,2-bromothiophene obtained 0.86 electrons in total,and Rh(111)surface lost 2.08 electrons in all. 相似文献
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In situ scanning tunneling microscopy (STM) was used to examine the structure of thiocyanate adlayers specifically adsorbed
on Rh(111) in solutions of potassium hydroxide and perchloric acid, both containing potassium thiocyanate (KSCN). An atomically
flat terrace-step structure was consistently observed on Rh(111) surfaces prepared by the flame-annealing-quenching method.
The Rh(111)-(1 × 1) atomic structure was discerned on the atomically flat terrace even in the alkaline solution. High-resolution
STM images disclosed two different structures of the SCN− adlayers, () and (2 × 2), in the alkaline and the acidic media, respectively. In each structure, an individual adsorbed SCN− ion appeared as a single spot with a constant corrugation height in STM images, suggesting that SCN− ions adsorbed predominantly with their
S-ends at particular bonding sites on Rh(111). The difference in the adlayer structure in the two solutions can be attributed
to the interaction between adsorbed SCN− and coadsorbed K+ in the alkaline solution, and is different from that between adsorbed SCN− and H+ in the acidic solution.
Received: 26 February 1997 / Accepted: 3 March 1997 相似文献
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Jie Wei Reihaneh Amirbeigiarab Yan‐Xia Chen Sung Sakong Axel Gross Olaf M. Magnussen 《Angewandte Chemie (International ed. in English)》2020,59(15):6182-6186
CO adlayers on Pt(111) electrode surfaces are an important electrochemical system and of great relevance to electrocatalysis. The potential‐dependent structure and dynamics of these adlayers are complex and still controversial, especially in the CO pre‐oxidation regime. We here employ in situ high‐speed scanning tunneling microscopy for studying the surface phase behavior in CO‐saturated 0.1 m H2SO4 on the millisecond time scale. At potentials near the onset of CO pre‐oxidation local fluctuations in the (2×2)‐CO adlayer are observed, which increase towards more positive potentials. Above 0.20 V (vs. Ag/AgCl), this leads to an adlayer where COad apparently reside on every top site, but still exhibit a (2×2) superstructure modulation. We interpret this observation as a dynamic effect, caused by a small number of highly mobile point defects in the (2×2)‐CO adlayer. As shown by density functional theory calculations, the CO lattice near such defects relaxes into a local (1×1) arrangement, which can rapidly propagate across the surface. This scenario, where a static (2×2) COad sublattice coexists with a highly dynamic sublattice of partially occupied top sites, explains the pronounced COad surface mobility during electrooxidation. 相似文献
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Angel Cuesta María del Carmen Pérez Alejandro Rincón Claudio Gutiérrez 《Chemphyschem》2006,7(11):2346-2351
We have determined, for the first time, the equilibrium CO coverage of Pt(111) electrodes at room temperature in 0.1 M H(2)SO(4) as a function of the CO partial pressure using CO-stripping cyclic voltammetry. Fourier-transform infrared (FT-IR) spectroscopy was used to confirm qualitatively the coverage values obtained. 相似文献
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用群分解EHMO法研究了苯在Rh(111)面上的化学吸附和成键性质。以Rh_7原子簇模型模拟Rh(111)表面,得到结合能为41kJ/mol,吸附高度2.60。被吸附的苯分子通过π键和金属原子的d轨道相互作用而受到活化,有利于在(111)表而上的化学反应。 相似文献
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Thiophene adsorption on the Rh(111) surfaces has been investigated by density functional theory.The results show that the adsorption at the hollow and bridge sites is the most stable.The molecular plane of the thiophene ring is distorted,the C=C bond is stretched to 1.448 and the C-C bond is shortened to 1.390.The C-H bonds tilt 22~42oaway from the surface.The calculated adsorption geometries are in reasonable agreement with population analysis and density of states.The thiophene molecule obtains 0.74 electrons,reflecting the interaction between the lone pair of sulfur and the d-orbitals of metal.The reaction paths and transition states for desulfurization of the molecule have been investigated.The bridge adsorption structure of thiophene leads to a thiol via an activated reaction with an energetic barrier of 0.30 eV.This second step is slightly difficult,and dissociation into a C4H4 fragment and a sulfur atom is possible,with an energetic barrier of 0.40 eV. 相似文献
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Christine M Welch Olga Nekrassova Xuan Dai Michael E Hyde Richard G Compton 《Chemphyschem》2004,5(9):1405-1410
The tabrication, characterisation, and electroanalytical application of gold and gold amalgam nanoparticles on glassy carbon electrodes is examined. Once the deposition parameters for gold nanoparticle electrodes were optimised, the analytical utility of the electrodes was examined in CrIII electroanalysis. It was found that gold nanoparticle modified (Au-NM) electrodes possess higher sensitivity than gold macroelectrodes. In addition, gold amalgam nanoparticle modified (AuHg-NM) electrodes were fabricated and characterised. The response of those electrodes was recorded in the presence of important environmental analytes (heavy metal cations). It was found AuHg-NM electrodes demonstrate a unique voltammetric behaviour and can be applied for electroanalysis when enhanced sensitivity is crucial. 相似文献
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PAN Gebo LI Huijing YUAN Qunhui CHEN Yongjun WAN Lijun & BAI Chunli Institute of Chemistry Chinese Academy of Sciences Beijing China 《中国科学B辑(英文版)》2004,47(4)
Self-organized systems have attracted much at-tention due to their potential applications in nano- technology as a bottom-up?approach for the con-struction of molecule-scale devices and nanostruc-tures[1—4]. Beyond the self-assembly of small molecu-lar building blocks, Schnherr et al. recently suc-ceeded in arranging the rosette supramolecular nanos-tructures in two dimensions on HOPG[5,6]. Moreover, interest has tremendously increased in the su-pramolecular structures via coordination-dr… 相似文献
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Formation of volatile nickel carbonyls with CO in catalytic reaction is one of the mechanisms of catalyst deactivation. CO is one of the most popular probe molecules to study the surface properties in model catalysis. Under ultra-high vacuum (UHV) conditions, the problem of nickel carbonyl impurity almost does not exist in the case that a high purity of CO is used directly. While in the near ambient pressure (NAP) range, nickel carbonyl is easily found on the surface by passing through the Ni containing tubes. Here, the NAP techniques such as NAP-X-ray photoelectron spectroscopy and NAP-scanning tunneling microscopy are used to study the adsorption of nickel carbonyl contaminated CO gas on Cu(111) surface in UHV and NAP conditions. By controlling the pressure of contaminated CO, the Ni-Cu bimetallic catalyst can form on Cu(111) surface. Furthermore, we investigate the process of CO adsorption and dissociation on the formed Ni-Cu bi-metal surface, and several high-pressure phases of CO structures are reported. This work contributes to understanding the interaction of nickel carbonyl with Cu(111) at room temperature, and reminds the consideration of CO molecules contaminated by nickel carbonyl especially in the NAP range study. 相似文献
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应用AES,LEED,XPS和TDS研究了Rh(100)上Sm膜和Sm/Rh表面合金以及CO在这两类模型表面的吸附与反应.室温下Sm在Rh(100)上的生长遵从SK模式,Sm膜经900K高温退火后可形成有序表面合金.在室温制备的Sm膜/Rh(100)表面上,室温下CO在Sm上的吸附改变了表面结构,生成SmOx和表面碳.随着Sm覆盖度的增加,低温脱附峰(α-CO)面积迅速下降,且峰温向高温方向位移;表明Sm的空间位阻和电子效应同时起作用.在Sm/Rh合金表面上,CO在约590K出现新的脱附峰,可归属为受Sm电正性修饰的Rh原子上的CO脱附峰 相似文献
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Dongyan Shen Yong Liu Dr. Guangxing Yang Prof. Hao Yu Prof. Feng Peng 《Chemphyschem》2019,20(21):2791-2798
A detailed understanding of the electrochemistry of platinum electrodes is of great importance for the electrochemical oxidation of fuels and electrochemical reduction of dioxygen in fuel cells. The Pt(111) facet is the most representative model mimicking Pt nanoparticles and polycrystals for fundamental studies. Herein, we propose a site-specific model accompanied with the typical elementary steps of the electrochemistry of Pt(111) in non-adsorbing electrolyte within the potential range between 0.05 and 1.15 V versus reversible hydrogen electrode. Simulations were conducted at different scanning rates based on the kinetics models. We reproduce all the anodic and cathodic peaks observed in the reported experimental curves. These results demonstrate the underlying mechanisms of the peak formation in different potential regions. 相似文献