Download or read book Metal Support Interaction and Electrochemical Promotion of Nano Structured Catalysts for the Reverse Water Gas Shift Reaction written by Christopher Panaritis and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The continued release of fossil-fuel derived carbon dioxide (CO2) emissions into our atmosphere led humanity into a climate and ecological crisis. Converting CO2 into valuable chemicals and fuels will replace and diminish the need for fossil fuel-derived products. Through the use of a catalyst, CO2 can be transformed into a commodity chemical by the reverse water gas shift (RWGS) reaction, where CO2 reacts with renewable hydrogen (H2) to form carbon monoxide (CO). CO then acts as the source molecule in the Fischer-Tropsch (FT) synthesis to form a range of hydrocarbons to manufacture chemicals and fuels. While the FT synthesis is a mature process, the conversion of CO2 into CO has yet to be made commercially available due to the constraints associated with high reaction temperature and catalytic stability. Noble metal ruthenium (Ru) has been widely used for the RWGS reaction due to its high catalytic activity, however, several constraints hinder its practical use, associated with its high cost and its susceptibility to deactivation. The doping or bimetallic use of non-noble metals iron (Fe) and cobalt (Co) is an attractive option to lower material cost and tailor the selectivity of the CO2 conversion towards the RWGS reaction without compromising catalytic activity. Furthermore, employing nanostructured catalysts as nanoparticles is a viable solution to further lower the amount of metal used and utilize the highly active surface area of the catalyst. Dispersing nanoparticles on ionically conductive supports/solid electrolytes which contain species like O2−, H+, Na+, and K+, provide an approach to further enhance the reaction. This phenomenon is referred to as metal-support interaction (MSI), allowing for the ions to back spillover from the support and onto the catalyst surface. An in-situ approach referred to as Non-Faradaic Modification of catalytic activity (NEMCA), also known as electrochemical promotion of catalysis (EPOC) is used to in-situ control the movement of ionic species from the solid electrolyte to and away from the catalyst. Both the MSI and EPOC phenomena have been shown to be functionally equivalent, meaning the ionic species act to alter the work function of the catalyst by forming an effective neutral double layer on the surface, which in turn alters the binding energy of the reactant and intermediate species to promote the reaction. The main objective of this work is to develop a catalyst that is highly active and selective to the RWGS reaction at low temperatures (

Download or read book Connecting Metal Support Interaction and Electrochemical Promotion Phenomena for Nano structured Catalysts written by Holly Dole and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Electrochemical Promotion and Metal Support Interaction on Catalytic Performance of Nano catalysts written by Yasmine Hajar and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In heterogeneous catalysis, promoting the activity of the catalytic metals is long known as an important method to make a process more efficient and viable. Noble metals have been promoted classically by a chemical coverage of an ionic solution on the surface of the catalyst or using inert support, e.g., silica or alumina, allowing an increase of the dispersion of the catalyst. Therefore, new methods of promotion needed to be better explored to improve the efficiency of metal and metal oxide catalysts. One way of enhancing the catalyst's activity is to disperse the noble metal at the nanoscale using an active type of support that is ion-conducting. Not only lattice ions can be exchanged with the surface of the nanoparticles but it can also engage in the oxidation reaction on the surface, resulting in what is known as metal-support interaction (MSI). Another method of improving the catalytic activity is to polarize the catalyst, allowing ions to migrate from a solid electrolyte to the gas-exposed surface, in a phenomenon known as electrochemical promotion of catalysis (EPOC). The change in the ions concentration on the surface would change the adsorption energy of the gaseous reactants and enhance or supress the catalytic rate. In this thesis, the effect of supporting nanoparticles of noble and non-noble metal (oxides) (Pt, Ru, Ir, Ni) was studied for the case of ionic and ionic-electronic conducting supports (CeO2, TiO2, YSZ). The enhancement in their catalytic rate was found and correlated to an electrochemical property, the exchange current density. Then, using isotopically-labeled oxygen, the oxygen exchange ability of the conductive oxides was evaluated when supporting Ir and Ru nanoparticles and correlated with the results from C3H8 isotopic oxidation reaction, which showed the extent of involvement of oxygen from the support as carried by the isotopically-labeled CO2 produced. Following this, electrochemical promotion of catalysis experiments were performed for different reactant/catalyst systems (C2H4 - Pt, Ru; C3H8 - Pt; CH4 - Pd, Ni9Pd). In the first system, the main outcome was the functional equivalence found for the MSI and EPOC effect in promoting the catalysts as experiments were performed at different temperatures, reactants partial pressures and polarization values. In the case of C3H8/Pt, the novel dispersion of Pt on an intermediate supporting layer (LSM/GDC) was found as a feasible method to obtain long stability of the catalyst while electrochemically promoting the rate of reaction. For CH4 oxidation, the polarization of the Pd nanoparticles showed continuous oxidation of the bulk of the catalyst resulting in a continuous increase of the catalytic rate. The Ni9Pd synthesized in a way to form a core/double-shell layer of Ni/Pd resulted in an enhanced catalytic rate and enhanced stability compared to stand-alone Pd. And lastly, to comprehend the ions' effect in the electrochemical promotion and the non-Faradaic nature of the phenomena, density-functional theory (DFT) modeling was used to demonstrate the increase of the heat of adsorption of reactants depending on their electronegative/positive nature.

Download or read book Encyclopedia of Renewable Energy Sustainability and the Environment written by and published by Elsevier. This book was released on 2024-10-01 with total page 4061 pages. Available in PDF, EPUB and Kindle. Book excerpt: Encyclopedia of Renewable Energy, Sustainability and the Environment, Four Volume Set comprehensively covers all renewable energy resources, including wind, solar, hydro, biomass, geothermal energy, and nuclear power, to name a few. In addition to covering the breadth of renewable energy resources at a fundamental level, this encyclopedia delves into the utilization and ideal applications of each resource and assesses them from environmental, economic, and policy standpoints. This book will serve as an ideal introduction to any renewable energy source for students, while also allowing them to learn about a topic in more depth and explore related topics, all in a single resource. Instructors, researchers, and industry professionals will also benefit from this comprehensive reference. Covers all renewable energy technologies in one comprehensive resource“/li> Details renewable energies’ processes, from production to utilization in a single encyclopedia Organizes topics into concise, consistently formatted chapters, perfect for readers who are new to the field Assesses economic challenges faced to implement each type of renewable energy Addresses the challenges of replacing fossil fuels with renewables and covers the environmental impacts of each renewable energy

Download or read book Nanostructured Transition Metal Sulfide Catalysts for Electrochemical Water Splitting written by Alex Wiltrout and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: With the worlds population steadily on the rise, there will continue to be an ever-increasing demand for energy. However, fossil fuels, which currently supply the world with an overwhelming portion of its energy needs, are quickly becoming depleted at a much faster rate than they are being generated. Most people use fossil fuels for their everyday energy needs, namely because compared to other alternative energy sources, it is cheaper and much more readily accessible. However, if one is looking to invest in a sustainable, long-term solution to the energy crisis that we currently face, these non-renewable energy sources are less than ideal. One possible solution to this problem is to begin using hydrogen as a fuel source instead. Hydrogen is an ideal alternative for a number of reasons, namely because it possesses the largest energy density by mass of any element, and that burning it produces no harmful byproducts, only water. The current industry standard for hydrogen production is primarily limited to production via steam-methane reformation and the water-gas shift reaction. However, these processes are not ideal for large-scale hydrogen production, and are detrimental to the environment because of the large amounts of CO and CO2 that are produced. One potentially cleaner alternative is proposed through electrochemical water splitting, whereby water is decomposed in hydrogen and oxygen. However, materials that catalyze these reactions are often quite rare and expensive, examples being Pt and IrO2. For this reason, the work hereafter aims to seek out new Earth-abundant materials, with a focus on transition metal sulfide systems, which can be used as catalysts to help catalyze the decomposition of water. Our work begins by investigating the catalytic activity of CuCo2S4 nanoparticles for the oxygen evolution reaction. Much of the focus insofar has been primarily concerned with transition metal oxide-based materials, however, metal sulfide systems are slowly gaining momentum. Those that do exist and have been tested for the oxygen evolution reaction (OER), often show moderate activity. By introducing additional elements into the system, we hope to further enhance the materials OER activity. Highly crystalline and nonagglomerated colloidal CuCo2S4 nanoparticles, which were previously inaccessible in the literature, were synthesized using low-temperature, solution-based synthetic routes. The CuCo2S4 nanoparticles were found to be highly active for OER under strongly alkaline conditions. Surface studies of the material suggest that mixed-metal sulfides, such as CuCo2S4, may in fact serve as precursors to oxides and/or hydroxides, which are likely the catalytically active species in solution. In addition to the work on the OER half reaction, a number of cobalt (Co3S4, CoS, Co9S8) and nickel sulfide (Ni3S2, -NiS, Ni9S8, Ni3S4) nanoparticle systems were investigated for use as potential hydrogen evolution reaction (HER) electrocatalysts. These materials were the target of this study because of their relatively low cost and high abundance within the Earths crust, as well as because they are know hydrodesulfurization (HDS) catalysts. Both HER and HDS rely upon a process by which hydrogen reversibly binds to the surface of a material. The hope was that one could then selectively target active HER catalysts, by identifying what materials are also good HDS catalysts. However, upon testing the cobalt and nickel sulfide nanoparticles, a correlation between HER and HDS could not be discerned.

Download or read book Strong Metal support Interactions written by R. T. K. Baker and published by . This book was released on 1986 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Metal Oxide Based Nanostructured Electrocatalysts for Fuel Cells Electrolyzers and Metal Air Batteries written by Teko Napporn and published by Elsevier. This book was released on 2021-01-30 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal Oxide-Based Nanostructured Electrocatalysts for Fuel Cells, Electrolyzers, and Metal-Air Batteries is a comprehensive book summarizing the recent overview of these new materials developed to date. The book is motivated by research that focuses on the reduction of noble metal content in catalysts to reduce the cost associated to the entire system. Metal oxides gained significant interest in heterogeneous catalysis for basic research and industrial deployment. Metal Oxide-Based Nanostructured Electrocatalysts for Fuel Cells, Electrolyzers, and Metal-Air Batteries puts these opportunities and challenges into a broad context, discusses the recent researches and technological advances, and finally provides several pathways and guidelines that could inspire the development of ground-breaking electrochemical devices for energy production or storage. Its primary focus is how materials development is an important approach to produce electricity for key applications such as automotive and industrial. The book is appropriate for those working in academia and R&D in the disciplines of materials science, chemistry, electrochemistry, and engineering. Includes key aspects of materials design to improve the performance of electrode materials for energy conversion and storage device applications Reviews emerging metal oxide materials for hydrogen production, hydrogen oxidation, oxygen reduction and oxygen evolution Discusses metal oxide electrocatalysts for water-splitting, metal-air batteries, electrolyzer, and fuel cell applications

Download or read book Rational Design and Synthesis of Inorganic Nanostructures for Tandem Catalysis and CO2 Conversion written by Chenlu Xie and published by . This book was released on 2018 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: The subject of this dissertation focuses on the design and synthesis of new catalysts with well-defined structures and superior performance to meet the new challenges in heterogenous catalysis. The past decade has witness the development of nanoscience as well as the inorganic catalysts for industrial applications, however there are still fundamental challenges and practical need for catalysis. Specifically, it is desirable to have the ability to selectivity produce complex molecules from simple components. Another great challenge faced by the modern industry is being environmentally friendly, and going for a carbon neutral economy would require using CO2 as feedstock to produce valuable products. The work herein focuses on the design and synthesis of inorganic nanocrystal catalysts that address these challenges by achieving selective and sequential chemical reactions and conversion of CO2 to valuable products. Chapter 1 introduces the development of heterogenous catalysis and the colloidal synthesis of metal nanoparticles catalysts with well-controlled structure. Tremendous efforts have been devoted to understanding the nucleation and growth process in the colloidal synthesis and developing new methods to produce metal nanoparticles with controlled sizes, shapes, composition. These well-defined catalytic system shows promising catalytic performance, which can be modulated by their structure (size, shape, compositions and the metal-oxide interfaces). The chapters hereafter explore the synthesis of new catalysts with controlled structures for catalysis. Chapter 2 presents the design and synthesis of a three dimensional (3D) nanostructured catalysts CeO2-Pt@mSiO2 with dual metal-oxide interfaces to study the tandem hydroformylation reaction in gas phase, where CO and H2 produced by methanol decomposition (catalyzed by CeO2-Pt interface) were reacted with ethylene to selectively yield propyl aldehyde (catalyzed by Pt-SiO2 interface). With the stable core-shell architecture and well-defined metal-oxide interfaces, the origin of the high propyl aldehyde selectivity over ethane, the dominant byproduct in conventional hydroformylation, was revealed by in-depth mechanism study and attributed to the synergybetween the two sequential reactions and the altered elementary reaction steps of the tandem reaction compared to the single-step reaction. The effective production of aldehyde through the tandem hydroformylation was also observed on other light olefin system, such as propylene and 1-butene. Chapter 3 expands the strategy of tandem catalysis into conversion of CO2 with hydrogen to value-added C2-C4 hydrocarbons, which is a major pursuit in clean energy research. Another well-defined 3D catalyst CeO2–Pt@mSiO2–Co was designed and synthesized, and CO2 was converted to C2-C4 hydrocarbons with 60% selectivity on this catalyst via reverse water gas shift reaction and subsequent Fischer–Tropsch process. In addition, the catalysts is stable and shows no obvious deactivation over 40 h. The successful production of C2−C4 hydrocarbons via a tandem process on a rationally designed, structurally well-defined catalyst demonstrates the power of sophisticated structure control in designing nanostructured catalysts for multiple-step chemical conversions. Chapter 4 turns to electrochemistry and apply the precision in catalyst structural design to the development of electrocatalysts for CO2 reduction. Herein, atomic ordering of bimetallic nanoparticles were synthetically tuned, from disordered alloy to ordered intermetallic, and it showed that this atomic level control over nanocrystal catalysts could give significant performance benefits in electrochemical CO2 reduction to CO. Atomic-level structural investigations revealed the atomic gold layers over the intermetallic core to be sufficient for enhanced catalytic behavior, which is further supported by DFT analysis.

Download or read book Electrochemical Activation of Catalysis written by Costas G. Vayenas and published by Springer Science & Business Media. This book was released on 2007-05-08 with total page 597 pages. Available in PDF, EPUB and Kindle. Book excerpt: I knew nothing of the work of C. G. Vayenas on NEMCA until the early nineties. Then I learned from a paper of his idea (gas interface reactions could be catalyzed electrochemically), which seemed quite marvelous; but I did not understand how it worked. Consequently, I decided to correspond with Professor Vayenas in Patras, Greece, to reach a better understanding of this concept. I think that my early papers (1946, 1947, and 1957), on the relationship between the work function of metal surfaces and electron transfer reactions thereat to particles in solution, held me in good stead to be receptive to what Vayenas told me. As the electrode potential changes, so of course, does the work function at the interface, and gas metal reactions there involve adsorbed particles which have bonding to the surface. Whether electron transfer is complete in such a case, or whether the effect is on the desorption of radicals, the work function determines the strength of their bonding, and if one varies the work function by varying the electrode potential, one can vary the reaction rate at the interface. I got the idea. After that, it has been smooth sailing. Dr. Vayenas wrote a seminal article in Modern Aspects of Electrochemistry, Number 29, and brought the field into the public eye. It has since grown and its usefulness in chemical catalytic reactions has been demonstrated and verified worldwide.

Download or read book Strong metal support interaction of Pt based electrocatalysts with transition metal oxides nitrides carbides for oxygen reduction reaction written by Min Chen and published by OAE Publishing Inc.. This book was released on 2023-06-06 with total page 31 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Metal Nanoparticles Over Active Ionic Conductive Supports for the Reverse Water Gas Shift Reaction written by Raha Einakchi and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Electrochemical water splitting based on metal oxide composite nanostructures written by Aneela Tahira and published by Linköping University Electronic Press. This book was released on 2020-05-14 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: The occurrence of available energy reservoirs is decreasing steeply, therefore we are looking for an alternative and sustainable renewable energy resources. Among them, hydrogen is considered as green fuel with a high density of energy. In nature, hydrogen is not found in a free state and it is most likely present in the compound form for example H2O. Water covers almost 75% of the earth planet. To produce hydrogen from water, it requires an efficient catalyst. For this purpose, noble materials such as Pt, Ir, and Ru are efficient materials for water splitting. These precious catalysts are rare in nature, very costly, and are restricted from largescale applications. Therefore, search for a new earth-abundant and nonprecious materials is a hot spot area in the research today. Among the materials, nanomaterials are excellent candidates because of their potential properties for extended applications, particularly in energy systems. The fabrication of nanostructured materials with high specific surface area, fast charge transport, rich catalytic sites, and huge ion transport is the key challenge for turning nonprecious materials into precious catalytic materials. In this thesis, we have investigated nonprecious nanostructured materials and they are found to be efficient for electrochemical water splitting. These nanostructured materials include MoS2-TiO2, MoS2, TiO2, MoSx@NiO, NiO, nickeliron layered double hydroxide (NiFeLDH)/Co3O4, NiFeLDH, Co3O4, Cu-doped MoS2, Co3O4- CuO, CuO, etc. The composition, morphology, crystalline structure, and phase purities are investigated by a wide range of analytical instruments such as XPS, SEM, HRTEM, and XRD. The production of hydrogen/oxygen from water is obtained either in the acidic or alkaline media. Based on the functional characterization we believe that these newly produced nanostructured materials can be capitalized for the development of water splitting, batteries, and other energy-related devices.

Download or read book Metal Nanoparticles for Catalysis written by Franklin Tao and published by Royal Society of Chemistry. This book was released on 2014-06-12 with total page 285 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalysis is a central topic in chemical transformation and energy conversion. Thanks to the spectacular achievements of colloidal chemistry and the synthesis of nanomaterials over the last two decades, there have also been significant advances in nanoparticle catalysis. Catalysis on different metal nanostructures with well-defined structures and composition has been extensively studied. Metal nanocrystals synthesized with colloidal chemistry exhibit different catalytic performances in contrast to metal nanoparticles prepared with impregnation or deposition precipitation. Additionally, theoretical approaches in predicting catalysis performance and understanding catalytic mechanism on these metal nanocatalysts have made significant progress. Metal Nanoparticles for Catalysis is a comprehensive text on catalysis on Nanoparticles, looking at both their synthesis and applications. Chapter topics include nanoreactor catalysis; Pd nanoparticles in C-C coupling reactions; metal salt-based gold nanocatalysts; theoretical insights into metal nanocatalysts; and nanoparticle mediated clock reaction. This book bridges the gap between nanomaterials synthesis and characterization, and catalysis. As such, this text will be a valuable resource for postgraduate students and researchers in these exciting fields.

Download or read book Nano electrocatalyst for Oxygen Reduction Reaction written by Omar Solorza Feria and published by CRC Press. This book was released on 2024-06-21 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: Global warming switches our reliance from fossil fuels to green, sustainable renewable energy sources. Because of its promising nature, high-efficiency nano-electrocatalysts have sparked interest in renewable energy. Hydrogen fuel cell/polymer electrolyte membrane (PEM) vehicles are the most environmentally conscious electromobility vehicles, with a high energy density and quick refuelling technology, prompting the auto industry to launch a variety of PEM fuel cell vehicles around the world. Oxygen reduction reaction (ORR) primary research interests include fuel cells and metal-air batteries. The sluggish kinetic reaction of ORR, which is responsible for the rate-limiting reaction at the PEM fuel cell cathodic system, further decreases energy efficiency. Optimising ORR for market expansion with cost-effective and efficient nano-electrocatalysts, on the other hand, remains a challenge. The book covers fundamental ORR reaction kinetics theories, tools, and techniques. It also explains the nano electrocatalysts for ORR made of noble, non-noble, and nanocarbon materials. Finally, the book explores the applications of PEM fuel cells and metal-air batteries.

Download or read book Nanostructured Non Precious Oxygen Reduction Reaction Catalysts for Electrochemical Energy Applications written by Jason Wu and published by . This book was released on 2015 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fuel cell and state of the art battery technologies share a common electrochemical reaction in their operation. The oxygen reduction reaction (ORR) is a key phenomenon for the efficient operation for both electrochemical devices. However, ORR often suffers from slow kinetics and requires electrocatalysts to speed-up the reaction to practical levels. The use of platinum based catalysts has long been considered the most effective solution in improving ORR kinetics; however, platinum is an extremely expensive metal and is limited in world supply. It is critical to find alternative, non-precious catalysts to replace platinum catalysts. Heat treated non-precious catalysts produced through high temperature pyrolysis of temperatures over 600 °C are promising class of materials, showing high catalytic activity and stability in both acidic and alkaline conditions. However, heat treated non-precious catalysts do not match platinum based catalysts in terms of stability and activity. Furthermore, the active sites of heat treated non-precious catalysts are still under debate. In the present work, non-precious carbon catalysts were synthesized via pyrolysis of carbon in the presence of nitrogen and a transition metal then evaluated and characterized. Iron is chosen as the transition metal for all of the experiments as it is naturally abundant, relatively safe, and displays the highest activity amongst transition metals in this application. In fact, iron displays the highest redox potential which has been noted to be related to the binding of dioxygen species. A number of different catalysts were synthesized then studied by varying the synthesis conditions and precursors employed to increase the activity of non-precious carbon catalysts. First, a new nitrogen rich ligand is synthesized to be used as the nitrogen source during pyrolysis. This ligand will chelate with iron in the system and thus will help prevent agglomeration of iron particles during pyrolysis, resulting in many isolated active sites. The ratios of iron to ligand were varied and the affects of varying the mass of iron in the system on catalytic activity was studied. Following this work, support-less catalysts focusing on employing one-dimensional nanofiber structures were synthesized using polyacrylonitrile as the basis of producing one-dimensional nanofibers. One-dimensional nanofibrous electrocatalysts were synthesized via electrospinning a solution of polyacrylonitrile in DMF. Iron was added into the solution as well to ensure the electrospun fibers were well impregnated with iron. The resulting nanofibers were then pyrolyzed and the catalysts were evaluated and characterized. The results that followed indicated that surface area and porosity of catalysts plays a significant role in obtaining highly active catalysts. Highly porous carbon catalysts were then synthesized, evaluated, and characterized as a result of this discovery. These catalysts were produced via electrospinning an emulsion of polyacrylonitrile and fumed silica particles. After pyrolysis, these particles were removed by treating the catalyst with HF acid. The results of the work completed have shown that it is possible to produce non-precious catalysts that can replace platinum, bringing us a step closer to full commercialization of renewable energy devices.

Download or read book Nanostructure of Transition Metal and Metal Oxide for Electrocatalysis written by Yanjuan Gu and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Nanostructure of Transition Metal and Metal Oxide for Electrocatalysis" by Yanjuan, Gu, 谷艳娟, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled NANOSTRUCTURE OF TRANSITION METAL AND METAL OXIDE FOR ELECTROCATALYSIS Submitted by Gu Yan Juan for the degree of Doctor of Philosophy at The University of Hong Kong in August 2006 Pd, Pt, and Ru nanoparticles that were uniformly dispersed on multi-walled carbon nanotubes (MWNTs) were synthesized by vacuum pyrolysis using metal acetylacetonate as metal precursor, and the nanocomposites were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X- ray diffraction (XRD). The size and distribution of the nanoparticles were strongly affected by the reaction time, temperature, and the initial mass ratio of the metal precursors to MWNTs. The higher temperature, the smaller Pd nanoparticles were formed at the range of 250 to 500 C. The average size of the Pd nanoparticles increased with the increase in mass ratio of the metal precursors to MWNTs. The particle size of Pt and Ru showed little change with the change in mass ratio. Pt and Ru nanoparticles had the mean diameters of 3.00.6 and 2.50.4 nm when the mass ratio of Pt(acac) and Ru(acac) to 2 3 MWNTs was both 2:1 at 500 C. The electrocatalytic activity of Pt/MWNTs and PtRu/MWNTs was investigated at room temperature by cyclic voltammetry and chronoamperometry. All of the electrochemical results showed that the PtRu/MWNTs catalyst exhibit high activity for methanol oxidation that resulted from the high surface area of carbon nanotubes and the platinum/ruthenium nanoparticles. Compared with Pt/MWNTs, the onset potential is much lower and the ratio of forward anodic peak current to reverse anodic peak current is much higher for methanol oxidation. Pt Ru /MWNTs displayed the best electrocatalytic 45 55 activities among all carbon nanotubes supported Pt and PtRu catalysts. Hyperbranched RuO nanostructures can be formed through the oxidation of Ru nanoparticles at relatively low temperatures in air, which is a very simple and low cost method. The morphology of the RuO nanostructure is closely associated with the dispersivity of the Ru nanoparticles on the MWNTs. Cu, Pt and Pd nanoparticles are very effective catalysts in the formation of RuO hyperbranched nanostructures. The electrochemical studies of these nanorods demonstrated that they display characteristic properties of RuO (110) surface. The successful attachment of Pt nanoparticles to RuO surface through a simple, two-step chemically controlled procedure is reported. The effect of the single crystal structure of RuO nanorods on the electrocatalytic activity of Pt nanoparticles was investigated, showing that the presence of the RuO nanorods greatly increases the electrochemical activity of electrodes toward methanol oxidation, not only increasing the current density but also shifting the onset potential of methanol electrooxidation to over 200 mV lower than that on the Pt nanoparticle electrode. The results described here also demonstrate the ability of metal oxide nanorods to serve as a conductive support for fuel cell applications. DOI: 10.5353/th_b3777439 Subjects: Electrocatalysis Transition metals Nanoparticles Nanostructured materials Methanol - Oxidation

Download or read book Development of Molecular Transition metal Catalysts for the Reverse Water gas Shift Reaction and the Selective Transformation of Carbon Dioxide and Hydrogen to Formic Acid Esters and Methanol written by Niklas Franz Westhues and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: