Characterization of Platinum-Based Heterogeneous Electrocatalysts and Catalysis Modeling PDF Download

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Languages : en
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Author: Hongsun Kim
Publisher:
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Category :
Languages : en
Pages : 262

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Author: Radoslav Adzic
Publisher: Springer Nature
ISBN: 3030495663
Category : Science
Languages : en
Pages : 174

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This book describes a science and technology of a new type of electrocatalysts consisting of a single atomic layer of platinum on suitable supports. This development helped overcome three major obstacles—catalysts‘ cost, activity, and stability—for a broad range of fuel cell applications. The volume begins with a short introduction to the science of electrocatalysis, covering four reactions important for energy conversion in fuel cells. A description follows of the properties of metal monolayers on electrode surfaces, and underpotential deposition of metals. The authors then describe the concept of Pt monolayer electrocatalysts and its implications and their synthesis by galvanic displacement of less-noble metal monolayers and other methods. The main part of the book presents a discussion of catalysts’ characterization and catalytic properties of Pt monolayers for the four main reactions of electrochemical energy conversion: oxygen reduction and oxidation of hydrogen, methanol and ethanol. The book concludes with a treatment of scale-up syntheses, fuel cell tests, catalysts’ stability and application prospects.

Author: Andrzej Wieckowski
Publisher: CRC Press
ISBN: 0203912713
Category : Science
Languages : en
Pages : 970

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Illustrating developments in electrochemical nanotechnology, heterogeneous catalysis, surface science and theoretical modelling, this reference describes the manipulation, characterization, control, and application of nanoparticles for enhanced catalytic activity and selectivity. It also offers experimental and synthetic strategies in nanoscale surface science. This standard-setting work clariefies several practical methods used to control the size, shape, crystal structure, and composition of nanoparticles; simulate metal-support interactions; predict nanoparticle behavior; enhance catalytic rates in gas phases; and examine catalytic functions on wet and dry surfaces.

Author: Anton Tokarev
Publisher: LAP Lambert Academic Publishing
ISBN: 9783838309750
Category :
Languages : en
Pages : 128

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In the present work electrochemical methods, namely "cyclic voltammetry" and "in-situ catalyst potential measurements," were applied for ex-situ and in-situ studies of catalysts respectively. Lactose oxidation was used as a model reaction. The combination of these two electrochemical methods gives a possibility for continuous characterization of metal containing heterogeneous catalysts during all steps of their life cycle - from synthesis to complete deactivation. The purpose of the ex-situ approach was to develop a common electrochemical method to characterize all VIII group metal catalysts. General steps, which can be used for every platinum group metal without making any specification or requirements on their nature, were elaborated. Second electrochemical method related to catalyst potential measurements, can provide in-situ information about surface processes in heterogeneous catalytic reactions. Catalyst potential curves can be used to indicate different surface processes. The estimation can be done on the basis on typical patterns. The catalyst potential phenomenon was quantified applying the advanced kinetic expression based on proposed reaction mechanism.

Author: Philippe Serp
Publisher: John Wiley & Sons
ISBN: 3527830170
Category : Technology & Engineering
Languages : en
Pages : 912

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b”Supported Metal Single Atom CatalysisCovers all key aspects of supported metal single atom catalysts, an invaluable resource for academic researchers and industry professionals alike Single atom catalysis is one of the most innovative and dynamic research areas in catalysis science. Supported metal catalysts are used extensively across the chemical industry, ranging from fine and bulk chemical production to petrochemicals. Single atom catalysts (SACs) combine the advantages of both homogeneous and heterogeneous catalysts such as catalyst stability, activity, and high dispersion of the active phase. Supported Metal Single Atom Catalysis provides an authoritative and up-to-date overview of the emerging field, covering the synthesis, preparation, characterization, modeling, and applications of SACs. This comprehensive volume introduces the basic principles of single atom catalysis, describes metal oxide and carbon support materials for SAC preparation, presents characterization techniques and theoretical calculations, and discusses SACs in areas including selective hydrogenation, oxidation reactions, activation of small molecules, C-C bond formation, and biomedical applications. Highlights the activity, selectivity, and stability advantages of supported metal SACs compared to other heterogeneous catalysts Covers applications of SACs in thermal catalysis, electrocatalysis, and photocatalysis Includes chapters on single atom alloys and supported double and triple metal atom catalysts Discusses the prospects, challenges, and potential industrial applications of SACs Supported Metal Single Atom Catalysis is an indispensable reference for all those working in the fields of catalysis, solid-state chemistry, materials science, and spectroscopy, including catalytic chemists, organic chemists, electrochemists, theoretical chemists, and industrial chemists.

Author: Duygu Gerceker
Publisher:
ISBN:
Category :
Languages : en
Pages : 381

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Heterogeneous catalysis has contributed to human civilization in an overwhelming manner by allowing the development of efficient processes to transform natural resources into fuels and chemicals. Currently, dwindling fossil fuel resources and alarming level of environmental issues have entailed a search for the development of novel catalysts to be used in more sustainable processes that have lower carbon footprint. Recent advancements in computing technologies coupled with the progress in electronic structure calculation methods yielded density functional theory (DFT) calculations as a powerful tool in computational catalysis. Combined with experimental and characterization efforts, atomic-level understanding of the catalyst structure and reaction mechanisms obtained through DFT calculations can be employed in novel catalyst design with improved properties. In this dissertation, a combined theoretical and experimental approach is presented to study Pt-based catalysts for conversion of light alkanes. A rigorous understanding of atomic-scale properties of the catalyst is paramount for developing novel catalysts that would provide more efficient transformation of light alkanes derived from shale gas. By using extensive DFT calculations, reaction kinetics measurements, catalyst characterization techniques and microkinetic modeling, Pt and Pt-based bimetallic catalysts are investigated for reaction mechanism, structure-activity relationship, and product selectivity in ethylene production from ethane and methane. First, the Pt catalyst is examined to understand ethane dehydrogenation mechanism and origins of coking that curtails its activity and stability. It is observed that the under-coordinated atoms at the step edge significantly contribute to the strong binding of the reaction intermediates and catalyze coke formation reactions. Then, various Pt-based bimetallic catalyst systems such as Pt-Sn, Pt-Zn, Pt-Pb, are studied by extensive DFT calculations coupled with ethane dehydrogenation reaction kinetics studies to identify the promotional effect of the addition of the second metal. It is observed that notably stepped sites of the catalyst surfaces become less active towards catalyzing deep dehydrogenation reaction due to geometric effects of alloying that decreased the binding strength of the reactants. For a further understanding of the reaction mechanism, a mean-field microkinetic model is also implemented for Pt and Pt-Sn catalysts. Following, DFT calculations for complete ethane dehydrogenation network are performed on Pt-Ir and Pt-Au catalysts to evaluate the reaction mechanism and promotional effects. Next, a descriptor-based approach to predict novel ethane dehydrogenation catalysts is presented using available DFT calculations and microkinetic modeling. As a complementary to the studies with using ethane as the feed, a study on non-oxidative methane conversion to ethylene and aromatics over Pt and Pt-Sn catalysts is also presented. It is demonstrated that Pt-Sn catalysts can be promising candidates for the reaction due to their comparable activity and selectivity with the state-of-the-art catalysts. Finally, a summary of the presented work is given, together with suggestions for future work.

Author: Albert Bruix Fusté
Publisher:
ISBN:
Category :
Languages : en
Pages : 199

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En aquesta tesi s'han utilitzat mètodes teòrics basats en la DFT per estudiar les propietats de sistemes formats per Pt i CeO2. Mitjançant un anàlisi de l'estructura electrònica i geomètrica dels models considerats, s'ha contribuït a la comprensió a nivell microscòpic de les interaccions entre Pt i CeO2. Així, s'han descrit els processos de transferència de càrrega entre diferents espècies de Pt i substrats de CeO2, resultant en l'oxidació de les espècies metàl·liques i la reducció de cations Ce. A més, s'ha demostrat que la presència del platí facilita la reducció de l'òxid de ceri a través de processos de migració (spillover) d'àtoms d'oxigen i que aquest efecte és més pronunciat quan el CeO2 és nanoestructurat. Això ha permès explicar per primera vegada els mecanismes de formació de vacants en catalitzadors basats en Pt i CeO2, que són responsables de la seva capacitat d'emmagatzemar oxigen i per tant, de la seva activitat catalítica. Amb els models de nanopartícules de CeO2, s'ha descrit l'existència de complexos d'adsorció on el Pt es troba dispersat atòmicament i en forma de catió a la superfície de les nanopartícules de cèria. A més, aquestes espècies es poden utilitzar com a electrocatalitzadors en els ànodes de cel·les de combustible, permetent el desenvolupament de dispositius que utilitzin platí de forma més eficient i, per tant, reduint-ne dràsticament els costos. L'estudi de la reactivitat de diferents espècies de Pt envers la reacció WGS mitjançant la determinació del perfil energètic de la dissociació de l'H2O ha permès caracteritzar els efectes que tenen la mida de la partícula de Pt i les interaccions metall-suport amb l'òxid de ceri en l'activitat d'aquests catalitzadors. S'ha demostrat l'excepcional activitat catalítica d'aquests sistemes i s'han identificat les propietats que els fan més reactius, superant en rendiment als catalitzadors que s'utilitzen industrialment per a catalitzar la WGS. Els estudis realitzats durant aquesta tesi han permès descriure detalladament propietats de sistemes formats per Pt i CeO2. Aquesta caracterització serveix per comprendre els sistemes catalítics basats en aquests materials i per guiar el disseny racional de nous materials amb les propietats catalítiques idònies per a cada aplicació.

Author:
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Category : Dissertations, Academic
Languages : en
Pages : 994

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Author: Sonam Patel
Publisher:
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Languages : en
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Platinum (Pt) and platinum alloys have attracted wide attention as catalysts to attain high performance to increase the power density and reduce the component cost of polymer electrolyte membrane fuel cells (PEMFCs). Extensive research has been conducted in the areas of new alloy development and understanding of mechanisms of electrochemical oxygen reduction reaction (ORR). The durability of PEMFCs is also a major barrier to the commercialization of these fuel cells. Recent studies have suggested that potential cycling can gradually lead to loss of active surface area due to Pt dissolution and nanoparticle grain growth [1]. In this thesis we report a one-step synthesis of highly-dispersed Pt nanoparticles and Pt- Cobalt supported on Ketjen carbon black (20% Pt/C & 20% Pt3Co/C) as electro-catalysts for PEMFCs. Pt particles with size in the range of ~ 2.6nm (Pt/C) and 3.9 nm (Pt3Co/C) were obtained through adsorption on carbon supports and subsequently thermal decomposition of platinum acetylacetonate (Pt(acac)2). A comparative characterization analysis, including X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM), FT-iR, EDAX, cyclic voltammetry (CV), and oxygen reduction reaction (ORR) activity, was performed on the synthesized and commercial (46.5wt% TKK) catalysts. The analysis was to reveal the Pt dispersion on the carbon support, particle size and distribution, electrochemical surface area (ECA), and ORR activities of these catalysts. It was found that the synthesized Pt/C showed similar particle size to that of the TKK catalysts (2.6nm and 2.7nm, respectively), but narrower particle size distribution; while the particle size for Pt3Co/C was found to be ~3.9 nm. Accelerated durability tests (ADT) under potential cycles were also performed for Pt/C and TKK to study the electrochemical degradation of the catalysts in corrosive environments. The ADTs revealed that the two catalysts (Pt/C & TKK) were comparable with respect to degradation in ECA and ORR activities. Initial electrochemical evaluation of Pt3Co/C was conducted, but durability studies were not attempted in this thesis due to its worse ORR kinetics than those of the Pt/C catalyst. From the experimental data, it was found that particle size impacted negatively the ECA and ORR activity of the catalysts.