Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 12 of 12 for “"Surface intermediates"”.
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Catalytic consequences of inner- and outer-sphere interactions at the solid-liquid interface in zeolites
… accounted for. Colloquially, interactions among surface intermediates bound directly to an active site are referred to as “inner-sphere” interactions, while those involving molecules within the second shell are known as “outer-sphere” interactions. This dissertation explores both inner- and …
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Spectroscopic and Kinetic Studies of Hydrodenitrogenation and Hydrodesulfurization over Supported Nickel Phosphide (Ni₂P)
… Transient and steady-state kinetics of a surface intermediate that is formed upon pyridine adsorption and reaction was studied to elucidate the mechanism of HDN over Ni₂P/SiO₂. Additionally, in situ FTIR and X-ray absorption near edge structure (XANES) spectroscopy was utilized to probe …
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Model Chromia Surface Chemistry: C<sub>2</sub> Alkyl Fragment Reactions and Probe Molecule Interactions
… on the nearly-stoichiometric α-Cr₂O₃ (102) surface results in the formation of gas phase hydrocarbons including ethylene, ethane, acetylene, 2-butene, 2-butyne and dihydrogen, and deposition of surface chlorine adatoms. No surface carbon or combustion products are observed in any reactions …
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Probing structure-function relationships at catalytic surfaces with emerging electroanalytical tools
In heterogeneous catalysis, adsorbed intermediates enable multi-step reaction pathways for otherwise energetically difficult chemical transformations. Understanding how catalyst surfaces impact the formation and reactivity of these adsorbed species is crucial to the rational design of new materials …
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Reactions of Halogenated Ethylenes on the α-Cr₂O₃ (101̅2) Surface
… ethylenes on the α-Cr₂O₃ (101̅2) single crystal surface results in the formation of gas phase hydrocarbons including acetylene, ethylene, butadiene, and dihydrogen, and deposition of surface chlorine adatoms. No surface carbon or combustion products are observed in any reactions indicating no …
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Catalytic, low temperature oxidation of methane into methanol over copper-exchanged zeolites
… shortcomings exist: 1) the location of surface intermediates on the zeolite is not well understood; 2) methane oxidation is stoichiometric, not catalytic; 3) there are few active sites and methanol yield is low. This work addresses all three shortcomings. First, a new reaction pathway is …
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Oxidation Chemistries Over Catalysts Containing M-N4 Active Sites
… had similar trends in predicted coverages of surface intermediates and calculated degrees of rate control based on regressed rate constants. Overall, these results support the choice of MPC hybrid materials as representative models for more heterogeneous M-N-Cs, and demonstrate their …
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A study of active sites on fibrillar alumina catalysts
… of such materials. It has been shown that the surface of alumina is quite complex and consists of several types of independent active sites. Three of these catalytic sites have been isolated in this work, and previous work has pin-pointed at least two more independent strong adsorption sites. …
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Mechanistic insights into the direct synthesis of H2O2 on transition metal catalysts
… proton-electron transfer to O2 and OOH surface intermediates, whereas, H2O forms by O-O bond rupture within OOH surface species. Direct synthesis, therefore, does not proceed by the Langmuir-Hinshelwood mechanism often invoked. Rather, H2O2 forms by heterolytic reaction pathways …
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The Electrochemical Nature of Non-Faradaic Catalysis at Interfaces
… state theory to analyze polarization-dependent surface reaction kinetics. This analysis shows how the electric field-dependence of interfacial reaction kinetics arises from partial charge transfer to form surface intermediates and transition states (i.e., the electrosorption valencies). This …
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Surface chemistry of metal oxide materials: from metalorganic and organic reactions to gas sensing
… It is not only used as a catalyst for various surface reactions but also as a catalytic support. Cu/ZnO is a commonly used industrial catalyst for methanol synthesis. In chapter 3, to understand the surface chemistry between Cucontaining species and ZnO substrate, we utilized the vacuum-based …
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Mechanistic and spectroscopic methods for identifying reactive intermediate structures and active site properties over metals, metal oxides, and metal phosphides
… correlate different catalyst properties (e.g., surface acidity, hydrophobicity, cluster size) under reaction conditions with changes in rates and selectivity. Here, we describe how the combination of kinetic measurements, density functional theory (DFT) calculations, and in situ spectroscopic …