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首页> 外文学位 >Model catalysts of ammonia synthesis and iron -water interfaces: A sum frequency generation vibrational spectroscopic study of solid -gas interfaces and anion photoelectron spectroscopic study of selected anion clusters.
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Model catalysts of ammonia synthesis and iron -water interfaces: A sum frequency generation vibrational spectroscopic study of solid -gas interfaces and anion photoelectron spectroscopic study of selected anion clusters.

机译：氨合成和铁-水界面的模型催化剂：固-气界面的总频率产生振动光谱研究和选定阴离子簇的阴离子光电子光谱研究。

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摘要

The ammonia synthesis reaction has been studied using single crystal model catalysis combined with sum frequency generation (SFG) vibrational spectroscopy. The adsorption of gases N2, H2, O2 and NH 3 that play a role in ammonia synthesis have been studied on the Fe(111) crystal surface by sum frequency generation vibrational spectroscopy using an integrated Ultra-High Vacuum (UHV)/high-pressure system. SFG spectra are presented for the dissociation intermediates, NH2 (∼3325 cm -1) and NH (∼3235 cm-1) under high pressure of ammonia or equilibrium concentrations of reactants and products on Fe(111) surfaces.;Special attention was paid to understand how potassium promotion of the iron catalyst affects the intermediates of ammonia synthesis. An Fe(111) surface promoted with 0.2 monolayers of potassium red shifts the vibrational frequencies of the reactive surface intermediates, NH and NH2, providing evidence for weakened the nitrogen-hydrogen bonds relative to clean Fe(111). Spectral features of these surface intermediates persisted to higher temperatures for promoted iron surfaces than for clean Fe(111) surfaces implying that nitrogen-iron bonds are stronger for the promoted surface. The ratio of the NH to NH 2 signal changed for promoted surfaces in the presence of equilibrium concentrations of reactants and products. The order of adding oxygen and potassium to promoted surfaces does not alter the spectra indicating that ammonia induces surface reconstruction of the catalyst to produce the same surface morphology.;When oxygen is co-adsorbed with nitrogen, hydrogen, ammonia or potassium on Fe(111), a relative phase shift of the spectra occurs as compared to the presence of adsorbates on clean iron surfaces.;Water adsorption on iron was also probed using SFG vibrational spectroscopy. For both H2O and D20, the only spectral feature was in the range of the free OH or free OD. From the absence of SFG spectra of ice-like structure we conclude that surface hydroxides are formed and no liquid water is present on the surface.;Other than model catalysis, gas phase anion photoelectron spectroscopy of the Cl + H2 van der Waals well, silicon clusters, germanium clusters, aluminum oxide clusters and indium phosphide clusters were studied. The spectra help to map out the neutral potential energy surfaces of the clusters. For aluminum oxide, the structures of the anions and neutrals were explored and for silicon, germanium and indium phosphide the electronic structure of larger clusters was mapped out.
机译：氨合成反应已使用单晶模型催化与总和频率产生（SFG）振动光谱法进行了研究。通过使用集成的超高真空（UHV）/高压的总频率发生振动光谱研究了Fe（111）晶体表面上吸附在氨合成中起作用的气体N2，H2，O2和NH 3的吸附系统。给出了在高压氨或平衡浓度的反应物和产物在Fe（111）表面上的离解中间体NH2（〜3325 cm -1）和NH（〜3235 cm-1）的SFG谱图;要特别注意了解铁催化剂的钾促进如何影响氨合成的中间体。 Fe（111）表面由0.2个单层的钾红促进，改变了反应性表面中间体NH和NH2的振动频率，提供了相对于纯净Fe（111）弱化氢氢键的证据。这些表面中间体的光谱特征持续存在于高温的铁表面上，而不是干净的Fe（111）表面，这意味着氮铁键对于增强的铁表面更强。在反应物和产物达到平衡浓度的情况下，对于被促进的表面，NH与NH 2信号的比率发生了变化。在被促进的表面上添加氧气和钾的顺序不会改变光谱，这表明氨会诱导催化剂的表面重建以产生相同的表面形态。;当氧气与氮，氢，氨或钾共同吸附在Fe（111）上时），与干净的铁表面上存在被吸附物相比，光谱发生了相对相移。;还使用SFG振动光谱法探测了铁上的水吸附。对于H2O和D20，唯一的光谱特征在游离OH或游离OD的范围内。由冰状结构的SFG谱图的缺乏得出的结论是，表面形成了氢氧化物，表面上没有液态水。;除模型催化作用外，Cl + H2范德华井的气相阴离子光电子能谱很好，硅研究了团簇，锗团簇，氧化铝团簇和磷化铟团簇。光谱有助于绘制群集的中性势能表面。对于氧化铝，探索了阴离子和中性的结构，对于硅，锗和磷化铟，绘制了较大簇的电子结构。

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  • 作者

    Ferguson, Michael James.;

  • 作者单位

    University of California, Berkeley.;

  • 授予单位 University of California, Berkeley.;
  • 学科 Chemistry Physical.
  • 学位 Ph.D.
  • 年度 2005
  • 页码 197 p.
  • 总页数 197
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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