Laser Diagnostics and Modeling of the Coupling Between Heterogeneous Catalytic and Gas-phase Oxidation of Hydrogen

Laser Diagnostics and Modeling of the Coupling Between Heterogeneous Catalytic and Gas-phase Oxidation of Hydrogen
Title Laser Diagnostics and Modeling of the Coupling Between Heterogeneous Catalytic and Gas-phase Oxidation of Hydrogen PDF eBook
Author Michael Försth
Publisher
Pages 78
Release 1998
Genre
ISBN

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Development of Combined Operando Diagnostics

Development of Combined Operando Diagnostics
Title Development of Combined Operando Diagnostics PDF eBook
Author Lisa Rämisch
Publisher
Pages 0
Release 2024
Genre
ISBN 9789180399982

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With the aim to bridge the pressure gap between traditional surface science and industrial applications, heterogeneous catalytic reactions on model catalysts are increasingly studied at near-ambient pressures. Under those conditions, the gas phase has been shown to play an important role during the interaction at the gas-surface interface making it complex to study. This complexity can be captured by simultaneously measuring different properties of the gas-surface interaction operando while the reaction takes place. Since each diagnostic tool offers unique information, combining them provides a fuller understanding of the reaction. This thesis presents a combination of three laser- and optical-based operando techniques that have been combined in a versatile in-house setup. We have shown that planar laser-induced fluorescence (PLIF), two dimensional-surface optical reflectance (2D-SOR) and polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS) can be combined, either simultaneously or in various configurations, to study CO oxidation on different Pd-based model catalysts. Thereby, chemical and structural information about the surface and chemical information about the gas phase can be obtained in space and temporally resolved. Moreover, some of the in-house optical techniques are combined with synchrotron-based techniques to extract more chemical and structural information than can be obtained from one measurement. This is demonstrated with simultaneous measurements combining PM-IRRAS and ambient pressure X-ray photoelectron spectroscopy (AP-XPS) for different gas-phase catalysis reactions and 2D-SOR with High Energy Surface X-ray Diffraction (HESXRD) for electrochemical studies.

Laser Diagnostics and Modeling of Combustion

Laser Diagnostics and Modeling of Combustion
Title Laser Diagnostics and Modeling of Combustion PDF eBook
Author Kazuo Iinuma
Publisher Springer
Pages 386
Release 1987
Genre Science
ISBN

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Modeling and Laser Diagnostic Experiments in Laser-assisted Chemical Vapor Deposition

Modeling and Laser Diagnostic Experiments in Laser-assisted Chemical Vapor Deposition
Title Modeling and Laser Diagnostic Experiments in Laser-assisted Chemical Vapor Deposition PDF eBook
Author David Clinton Skouby
Publisher
Pages 332
Release 1989
Genre
ISBN

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Scientific and Technical Aerospace Reports

Scientific and Technical Aerospace Reports
Title Scientific and Technical Aerospace Reports PDF eBook
Author
Publisher
Pages 1556
Release 1992
Genre Aeronautics
ISBN

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Bimodal Oxidation

Bimodal Oxidation
Title Bimodal Oxidation PDF eBook
Author Robert Bakhtchadjian
Publisher CRC Press
Pages 302
Release 2019-11-15
Genre Science
ISBN 1000084841

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This book is devoted to the problems of oxidation chemical reactions and addresses bimodal reaction sequences. Chemical reactions of oxidation, occurring under certain conditions and in multicomponent systems are complex processes. The process of the oxidation essentially changes in the presence and contact of the solid substances with reactants. The role of solid substances and the appearance of this phenomenon in oxidation reaction are discussed. The reader will understand the "driving forces" of this phenomenon and apply it in practice. Written for chemists, physicists, biologists and engineers working in the domain of oxidation reactions. Key Selling Features: Covers the historical background, modern state of the art, and perspectives in investigations of the coupling between heterogeneous and homogeneous reactions Discusses the feasible pathways of the coupling of heterogeneous and homogeneous reactions in oxidation in man-made and natural chemical systems Addresses the abundance, peculiarities and mechanisms of the bimodal reaction sequences in oxidation with dioxygen in recent decades Discusses the existence of the bimodal reaction sequences in chemical systems investigations in atmospheric chemistry and heterogeneous photocatalysis Presented in a simple concise style, accessible for both specialists and non-specialists

Relationships Between Gas-Phase Ionization Energies and Solution-Phase Oxidation Potentials: Applications to the Electrocatalytic Production of Hydrogen from Weak Acids

Relationships Between Gas-Phase Ionization Energies and Solution-Phase Oxidation Potentials: Applications to the Electrocatalytic Production of Hydrogen from Weak Acids
Title Relationships Between Gas-Phase Ionization Energies and Solution-Phase Oxidation Potentials: Applications to the Electrocatalytic Production of Hydrogen from Weak Acids PDF eBook
Author Takahiro Sakamoto
Publisher
Pages 596
Release 2010
Genre
ISBN

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The transfer of electrons to and from a molecule is one of the more fundamental and important chemical processes. One such important example is the reduction-oxidation (redox) cycles in catalysts and enzymes. In the hydrogenase enzymes, adding and removing electrons is one of the key processes for generating H2 from water molecules. Finding a direct free energy relation between the vertical ionization energies (IEV) measured spectroscopically by gas-phase photoelectron spectroscopy and the oxidation potentials (E1/2) measured thermodynamically in solution by cyclic voltammetry (CV) for molecules is an important aspect for developing effective catalysts. In this study, a series of organometallic compounds such as metallocenes were used for investigating the free energy relationships and catalysts inspired by the active sites of [FeFe]-hydrogenases enzymes were evaluated for their ability to produce H2 from electrocatalytic reduction of weak acids. The first part of the dissertation explores metallocenes of the form (ç5 C5H5)2M (M= Fe, Ru, Os, Co, Ni) as the model for developing the free energy relation between gas phase ionization energies (IEV) and solution oxidation potentials (E1/2). It was found that computing the electronic properties of Cp2Fe, Cp2Ru, and Cp2Os using VWN-Stoll and OPBE density functional theory (DFT) functional was successful with root mean square deviation (RMSD) of 0.02 eV between the experimental and calculated ionization energies. However, calculated ionization energies of Cp2Co and Cp2Ni were less successful with RMSD of 0.3 eV between the experimental and calculated ionization energies. Introduction of the B3LYP or M06 hybrid DFT functionals yielded much improved results (0.1 eV) over the previous combinations of DFT functional for Cp2Co and Cp2Ni. The energy relation between the two experimental measurements was established and further computational studies revealed that the solvation energy was the largest energy contribution between IEV and E1/2 in the five studied metallocenes. The RMSD of the calculated oxidation potentials, after adjusting for the error in gas phase ionization energies, was 0.09 V. The second part of the dissertation explores a series of catalysts inspired by the active sites of [FeFe]-hydrogenase enzymes; ì-(2,3-pyrazinedithiolato)diironhexacarbonyl (PzDT-cat), Fe2(ì-X2C5H8O)(CO)6 (where X = S, Se, Te), and Fe2(ì-1,3-SC3H6X)(CO)6 (where X = Se and Te) for their ability to produce H2 from weak acids utilizing the computational techniques and knowledge gained from the metallocene study. Even though the overall electronic perturbation from ì-(1,2-benzenedithiolato)diironhexacarbonyl (BDT-cat) to ì-(2,3-pyridinedithiolato)diironhexacarbonyl (PyDT-cat) to PzDT-cat is found to be small, the reduction potential of PzDT-cat was found to be 0.15 V less negative than that of BDT-cat resulting in less energy required for initiating electrocatalytic H2 production over the BDT-cat and PyDT-cat. Lower reorganization energy has been achieved by substitutions of larger chalcogens at the Fe2S2 core. However, the electrocatalytic production of H2 from acetic acid in acetonitrile was found to be diminished upon going from analogous S to Se to Te species. This is ascribed to the increase in the Fe-Fe bond distance with a corresponding increase in the size of the chalcogen atoms from S to Se to Te, disfavoring the formation of a carbonyl-bridged structure in the anion which is thought to be critical to the mechanism of H2 production.