Download or read book Utilization of First principles Based Models in the Mechanistic Studies of Thermocatalytic and Photocatalytic Processes on Transition Metal Surfaces written by Talin Avanesian and published by . This book was released on 2016 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work we utilized quantum chemical calculations coupled with numerical and analytical models to predict macroscopic observables associated with catalytic and photocatalytic processes on transition metal surfaces. All the predicted macroscopic observables were validated based on experimental measurements. The theoretical models developed here provide atomic scale insights into the mechanisms of catalytic and photocatalytic processes and suggest areas for future research in the design of novel catalysts.
Download or read book Mechanistic Studies for Catalytic Transformation of Small Oxygenates on Transition Metals written by Suyash Singh and published by . This book was released on 2014 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past century, heterogeneous catalysis has played a central role in the development of efficient chemical processes for the conversion of fossil resources to fuels and chemicals, and identification of new, sustainable routes to upgrade renewable carbon sources that minimize the ecological footprint. More recently, unprecedented advances in electronic structure theory and related computational methods have provided a major thrust to the efforts that utilize density function theory (DFT) calculations for developing fundamental atomic-level understanding of these processes, and subsequently designing new and improved catalysts. In this dissertation, a combined theoretical and experimental approach is presented to study the reaction mechanisms for the catalytic conversion of formic acid (FA) and propylene oxide on transition metals. An iterative methodology comprising of DFT calculations, reaction kinetics measurements, and mean-field microkinetic modeling is employed to determine the nature of active sites on supported catalysts, explain the experimentally observed trends, and obtain predictions for the surface environment under reaction conditions. A detailed analysis of the DFT derived thermochemistry and kinetics parameters over a wide range of transition metal surfaces is performed to identify the key reactivity descriptors for FA decomposition on transition metal catalysts, and develop semi-empirical linear correlations that are then used to develop a microkinetic modeling based framework for the identification and design of improved (active and selective) bimetallic alloy catalysts. Finally, the possible utilization and applications of these methods and ideas in other key chemical transformations are proposed, and suggestions for future work are included.
Download or read book Quantum Chemistry Studies of Catalytic and Photocatalytic Materials written by Anne Marie Shough and published by ProQuest. This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Various established and novel quantum chemistry methods are employed to investigate the properties of photocatalytic materials. Hybrid quantum mechanics/molecular mechanics (QM/MM) cluster models are developed, allowing accurate geometric and electronic structure predictions for one-dimensional O-Ti-O chains in the microporous titanosilicate ETS-10. This model is exploited to identify transition metal substituents capable of improving the photocatalytic properties of ETS-10. A detailed investigation of vanadium substitution is presented, supporting the presence of both V IV and V V states in experimental samples. Consistent with experimental results, visible-light band gap energies and improved charge separation are predicted for V-substituted ETS-10, establishing this material as a promising visible light photocatalyst. Transition metal substitution trends, based on seven transition metals, are used to develop linear models capable of rapidly estimating key features of the electronic structure for various transition metal combinations. These linear models predict that systems with small ionic radii (V V, Fe III) and high oxidation states (V V, Mo V) are favored for obtaining visible-light band gap energies within the visible range of the spectrum. Similar computational methods are used to investigate reaction mechanisms for the high temperature decomposition of Brønsted acid and hydroxyl nest sites in zeolite materials. The decomposition of these sites is generally attributed to a dehydration mechanism. However, comparable reaction energies are predicted for proposed dehydrogenation pathways, suggesting that both reactions are likely to occur. This is consistent with recent experimental reports that have identified H 2 as the primary product from thermally treated zeolites. Predicted geometries and optical absorption spectra of the proposed dehydrogenation products are consistent with experimental results, providing insight into the structure of active sites in zeolite materials used in high temperature industrial applications. In the final section, a new methodology, the poly-functional (PF) method, is developed for predicting thermochemical properties. This method employs linear combinations of enthalpy estimates from different density functionals, exploiting error correlations among the functionals and allowing for further improvements in accuracy. Unlike more costly methods, the PF method boasts a good compromise between accuracy and computational efforts making it useful for larger systems or where computational resources are limited. Opportunities to improve PF accuracy and implications for the development of future density functional theory are discussed.
Download or read book Mechanistic Studies of First row Homogeneous Transition Metal Catalysts written by Bas Venderbosch and published by . This book was released on 2020 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mechanistic Studies on Transition Metal and Biocatalytic Systems by Computer Modeling written by and published by . This book was released on 2008 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Towards a Molecular Scale Understanding of Surface Chemistry and Photocatalysis on Metal Oxides written by and published by . This book was released on 2015 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project has provided an increased understanding of molecular processes and structure-activity relationships in photocatalytic systems. This could ultimately lead to guidelines on how to make TiO2-based photocatalytic systems more efficient. This directly relates to the Program's mission to develop a mechanistic understanding of chemical reactions that pertain to environmental remediation and pollution control; energy production (photoelectrochemical and production of hydrogen); and novel materials synthesis.
Download or read book Mechanistic Studies and Design of Supported Transition Metal Complexes written by Terry Zhi Hao Gani and published by . This book was released on 2020 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: Supported transition metal (TM) complexes are an emerging class of materials with many potential applications in the chemical industry ranging from separations to catalysis. They offer increased tunability and often also improved performance over their bulk heterogeneous counterparts. Their study and rational design is, however, accompanied by several unique considerations and challenges that we address in this thesis. The first part of the thesis broadly develops and applies computational screening strategies for supported TM complexes. First, we detail how weak C-H[superscript ...]O hydrogen bonds can be exploited to increase selectivity of ferrocenium (Fc+)-based polymer electrode materials for formate adsorption over perchlorate adsorption while maintaining reasonable desorption rates in the reduced (ferrocene, Fc) state. Through a systematic characterization of formate and perchlorate interactions with a small (ca. 40) but diverse set of functionalized Fc+ complexes, we identify and rationalize design rules for functionalizations that simultaneously increase selectivity for formate in aqueous environments while permitting rapid release from Fc. Next, we screen a larger (ca. 500) set of model Fe(II) complexes for methane hydroxylation in order to assess if linear free energy relationships (LFERs), extensively developed to reduce the computational cost of computationally screening bulk heterogeneous catalysts, can also be applied to supported single-site TM catalysts. We demonstrate that structural distortions achievable in porous frameworks and chelating ligands break these LFERs by altering relative d-orbital splittings, thereby revealing a potential strategy for improving the activity of these catalysts. Finally, to address a particularly pervasive issue in density functional theory (DFT) studies of first-row open-shell TM complexes, we investigate how the fraction of exact exchange parameterized in the functional affects computed reaction and spin-splitting energies. We rationalize this sensitivity in terms of differences in metal-ligand electron delocalization and introduce the metal-ligand bond valence as a simple, yet robust, descriptor that unifies understanding of exchange sensitivity for catalytic properties and spin-state ordering in TM complexes.
Download or read book Mechanistic Insights Into Elevated Temperature Photocatalytic Processes Via Combined Experimental and Theoretical Approach written by Samiksha Poudyal and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Developing new catalytic technologies that allow for the production of fuels and building-block chemicals from CO2 and H2O photocatalytically is one of the greatest challenges of the 21st century. H2O and CO2 are difficult-to-activate molecules and their successful reduction is potentially kinetically limited. The studies presented herein are aimed at providing a detailed understanding of the reaction such that photocatalysts may be rationally selected and optimized. Our efforts also aim at developing photocatalysts and reactor design that allow utilization of full solar spectrum (UV-vis and IR), which could greatly enhance the overall quantum efficiency of the system. Elevated temperature is commonly avoided in photocatalysis due to the perception that high temperature leads to rapid exciton recombination and loss of quantum efficiency. Instead, enhanced catalytic activity is encountered in our study at autogenous temperatures (350°C+) produced through IR heating by employing a concentrated solar photoreaction (CSPR) approach. As we explore the photocatalytic synthesis of complex molecules, reaction mechanisms will involve more complex surface-bound intermediates of varying electronic character. This study highlights the interface between the classical electrochemical understanding of photocatalytic reactions where highly destabilized reaction intermediates are common and photocatalytic synthesis reactions where vibrational barriers may be contributing to active reaction pathways. Understanding the stability and electronic nature of these species on the catalyst surface may be crucial in dictating catalyst performance and selectivity. Our results have shed light onto several chemical and physical phenomena at the mechanistic level that drive elementary reaction steps on the surface. Some insights include the isolation of new H-transfer mechanisms and variation in surface chemistry under a range of experimental environments (variable temperature, variable chemical potential of reactants, kinetic isotope effect, etc.). Results indicate that photocatalyst with a high Debye temperature, robust bulk bonding, and elevated surface chemical reactivity could directly promote new reaction intermediates produced via thermal/vibrational routes that further enhance the selectivity towards hydrogenation. Identifying and understanding the effect of the stability of atomic H and how it is energetically driven through the reaction mechanism could dramatically enhance our ability to control selectivity in photocatalytic reaction mechanisms.
Download or read book Synthetic and Mechanistic Studies of Transition Metal Complexes written by John Arthur Broomhead and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mechanistic Studies of Some Reactions of Square Planar Transition Metal Complexes in Solution written by John Reginald Lyons and published by . This book was released on 1968 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Kinetic and Mechanistic Studies an the Interaction of Transition Metal Complexes with NO and Related Water Exchange Reactions written by Thorsten Schneppensieper and published by . This book was released on 2001 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Hydrocarbon Conversion Over Transition Metal Catalysts written by Zhi-Jian Zhao and published by . This book was released on 2012 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mechanistic Studies in Transition Metal Organic Chemistry written by D. Mead and published by . This book was released on 1970 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Semiconductor Photocatalysis written by Jiaguo Yu and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Surface Science written by K. Oura and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 443 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most important aspects of modern surface science are covered. All topics are presented in a concise and clear form accessible to a beginner. At the same time, the coverage is comprehensive and at a high technical level, with emphasis on the fundamental physical principles. Numerous examples, references, practice exercises, and problems complement this remarkably complete treatment, which will also serve as an excellent reference for researchers and practitioners. The textbook is idea for students in engineering and physical sciences.
Download or read book Photoelectrocatalysis written by Leonardo Palmisano and published by Elsevier. This book was released on 2022-10-21 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photoelectrocatalysis: Fundamentals and Applications presents an in-depth review of the topic for students and researchersworking on photoelectrocatalysis-related subjects from pure chemistry to materials and environmental chemistry inorder to propose applications and new perspectives. The main advantage of a photoelectrocatalytic process is the mildexperimental conditions under which the reactions are carried out, which are often possible at atmospheric pressure androom temperature using cheap and nontoxic solvents (e.g., water), oxidants (e.g., O2 from the air), catalytic materials (e.g.,TiO2 on Ti layer), and the potential exploitation of solar light. This book presents the fundamentals and the applications of photoelectrocatalysis, such as hydrogen production fromwater splitting, the remediation of harmful compounds, and CO2 reduction. Photoelectrocatalytic reactors and lightsources, in addition to kinetic aspects, are presented along with an exploration of the relationship between photocatalysisand electrocatalysis. In addition, photocorrosion issues and the application of selective photoelectrocatalytic organictransformations, which is now a growing field of research, are also reported. Finally, the advantages/disadvantages andfuture perspectives of photoelectrocatalysis are highlighted through the possibility of working at a pilot/industrial scale inenvironmentally friendly conditions. Presents the fundamentals of photoelectrocatalysis Outlines photoelectrocatalytic green chemistry Reviews photoelectrocatalytic remediation of harmful compounds, hydrogen production, and CO2 reduction Includes photocorrosion, photoelectrocatalytic reactors, and modeling along with kinetic aspects
Download or read book Bimetallic Catalysts written by John H. Sinfelt and published by Wiley-Interscience. This book was released on 1983-09-29 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents an account of the research on bimetallic catalysts. Focuses attention on the possibility of influencing the selectivity of chemical transformations on metal surfaces and preparing metal alloys in a highly dispersed state. Covers the validation and elucidation of the bimetallic cluster concept. Includes figures and tables.
