Download or read book Electrocatalysts Having Platium Monolayers on Palladium Palladium Alloy and Gold Alloy Core shell Nanoparticles and Uses Thereof written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The invention relates to platinum-coated particles useful as fuel cell electrocatalysts. The particles are composed of a noble metal or metal alloy core at least partially encapsulated by an atomically thin surface layer of platinum atoms. The invention particularly relates to such particles having a palladium, palladium alloy, gold alloy, or rhenium alloy core encapsulated by an atomic monolayer of platinum. In other embodiments, the invention relates to fuel cells containing these electrocatalysts and methods for generating electrical energy therefrom.

Download or read book Electrocatalysts Having Gold Monolayers on Platinum Nanoparticle Cores and Uses Thereof written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The invention relates to gold-coated particles useful as fuel cell electrocatalysts. The particles are composed of an electrocatalytically active core at least partially encapsulated by an outer shell of gold or gold alloy. The invention more particularly relates to such particles having a noble metal-containing core, and more particularly, a platinum or platinum alloy core. In other embodiments, the invention relates to fuel cells containing these electrocatalysts and methods for generating electrical energy therefrom.

Download or read book Platinum Monolayer Electrocatalysts written by Radoslav Adzic and published by Springer Nature. This book was released on 2020-08-11 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Synthesis and Characterization of Nanostructured Palladium based Alloy Electrocatalysts written by Arindam Sarkar and published by . This book was released on 2009 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: Low temperature fuel cells like proton exchange membrane fuel cells (PEMFC) are expected to play a crucial role in the future hydrogen economy, especially for transportation applications. These electrochemical devices offer significantly higher efficiency compared to conventional heat engines. However, use of exotic and expensive platinum as the electrocatalyst poses serious problems for commercial viability. In this regard, there is an urgent need to develop low-platinum or non-platinum electrocatalysts with electrocatalytic activity for the oxygen reduction reaction (ORR) superior or comparable to that of platinum. This dissertation first investigates non-platinum, palladium-based alloy electrocatalysts for ORR. Particularly, Pd-M (M = Mo and W) alloys are synthesized by a novel thermal decomposition of organo-metallic precursors. The carbon-supported Pd-M (M = Mo, W) electrocatalyts are then heat treated up to 900 °C in H2 atmosphere and investigated for their phase behavior. Cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements reveal that the alloying of Pd with Mo or W significantly enhances the catalytic activity for ORR as well as the stability (durability) of the electrocatalysts. Additionally, both the alloy systems exhibit high tolerance to methanol, which is particularly advantageous for direct methanol fuel cells (DMFC). The dissertation then focuses on one-pot synthesis of carbon-supported multi-metallic Pt-Pd-Co nanoalloys by a rapid microwave-assisted solvothermal (MW-ST) method. The multi-metallic alloy compositions synthesized by the MW-ST method show much higher catalytic activity for ORR compared to their counterparts synthesized by the conventional borohydride reduction method. Additionally, a series of Pt encapsulated Pd-Co nanoparticle electrocatalysts are synthesized by the MW-ST method and characterized to understand their phase behavior, surface composition, and electrocatalytic activity for ORR. Finally, the dissertation focuses on carbon-supported binary Pt@Cu and ternary PtxPd1-x@Cu "core-shell" nanoparticles synthesized by a novel galvanic displacement of Cu by Pt4+ and Pd2+ at ambient conditions. Structural characterizations suggest that the Pt@Cu nanoparticles have a Pt-Cu alloy layer sandwiched between a copper core and a Pt shell. The electrochemical data clearly point to an enhancement in the activity for ORR for the Pt@Cu "core-shell" nanoparticle electrocatalysts compared to the commercial Pt electrocatalyst, both on per unit mass of Pt and per unit active surface area basis. The increase in activity for ORR is ascribed to electronic modification of the outer Pt shell by the Pt-Cu alloy core. However, incorporation of Pd to obtain PtxPd1-x@Cu deteriorates the activity for ORR.

Download or read book Platinum and Platinum Alloy coated Palladium and Palladium Alloy Particles and Uses Thereof written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The present invention relates to particle and nanoparticle composites useful as oxygen-reduction electrocatalysts. The particle composites are composed of a palladium or palladium-alloy particle or nanoparticle substrate coated with an atomic submonolayer, monolayer, bilayer, or trilayer of zerovalent platinum atoms. The invention also relates to a catalyst and a fuel cell containing the particle or nanoparticle composites of the invention. The invention additionally includes methods for oxygen reduction and production of electrical energy by using the particle and nanoparticle composites of the invention.

Download or read book Palladium platinum Core shell Electrocatalysts for Oxygen Reduction Reaction Prepared with the Assistance of Citric Acid written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Core-shell structure is a promising alternative to solid platinum (Pt) nanoparticles as electrocatalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). A simple method of preparing palladium (Pd)-platinum (Pt) core-shell catalysts (Pd@Pt/C) in a gram-batch was developed with the assistance of citric acid. The Pt shell deposition involves three different pathways: galvanic displacement reaction between Pd atoms and Pt cations, chemical reduction by citric acid, and reduction by negative charges on Pd surfaces. The uniform ultrathin (~0.4 nm) Pt shell was characterized by in situ X-ray diffraction (XRD) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images combined with electron energy loss spectroscopy (EELS). Compared with state-of-the-art Pt/C, the Pd@Pt/C core-shell catalyst showed 4 times higher Pt mass activity and much better durability upon potential cycling. As a result, both the mass activity and durability were comparable to that of Pd@Pt/C synthesized by a Cu-mediated-Pt-displacement method, which is more complicated and difficult for mass production.

Download or read book Synthesis of Palladium gold Alloy Nanoparticle Catalysts for the Reduction of Nitrite in Water written by Sarah Seraj and published by . This book was released on 2018 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: Hydrogenation using palladium-based (Pd-based) catalysts has emerged as a promising treatment method for nitrate in drinking water. However, low catalytic activity and longevity can be a barrier to widespread adoption over conventional treatment methods. Controlling catalyst structure at the molecular scale is one approach to improving catalytic activity and longevity. Intermetallic palladium-gold nanoparticle (PdAu NP) alloy catalysts of varying composition were synthesized for nitrite reduction using a polyol reduction method and microwave-assisted heating. The average size of PdAu NPs was 4.1 ± 2.2 nm. Enhanced nitrite reduction has been previously observed for Pd combined with Au in a core-shell NP structure, but has not been studied for intermetallic PdAu alloy NPs. Moreover, the mechanism by which Au enhances Pd-catalyzed nitrite reduction is not well understood. The PdAu NPs were loaded into an amorphous silica support and evaluated for nitrite reduction in a batch reactor. Reaction followed pseudo first-order kinetics for greater than 80% of conversion. Catalyst activity showed volcano-like behavior with varying composition .... All PdAu alloys were significantly more active for nitrite reduction compared to pure Pd NPs, despite Au being catalytically inactive for hydrogenation. Sulfide fouling and catalyst longevity studies were conducted. The presence of Au in the catalyst structure did not appear to enhance resistance to sulfide fouling. Moreover, catalyst activity was reduced upon repeated cycles of nitrite reduction. Further investigation is required to understand the mechanism for catalyst deactivation.

Download or read book Gold promoted Structurally Ordered Intermetallic Palladium Cobalt Nanoparticles for the Oxygen Reduction Reaction written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Considerable efforts to make palladium and palladium alloys active catalysts and a possible replacement for platinum have had a marginal success. Here, we report on a structurally ordered Au10Pd40Co50 catalyst that exhibits comparable activity to conventional platinum catalysts in both acid and alkaline media. Electron microscopic techniques demonstrate that via addition of gold atoms PdCo nanoparticles undergo at elevated temperatures an atomic structural transition from core-shell to a rare intermetallic ordered structure with twin boundaries forming stable, and facets. The superior stability of this catalyst compared to platinum after 10,000 potential cycles in alkaline media is attributed to the atomic structural order of PdCo nanoparticles along with protective effect of clusters of gold atoms on the surface. This strategy of making ordered palladium intermetallic alloy nanoparticles can be used in diverse heterogeneous catalysis where particle size and structural stability matters.

Download or read book Gold Based Electro Catalysts written by Prabalini Sivasubramaniam and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Gold electrocatalysts have been of growing interest in recent years owing to their reactivity for a variety of important reactions such as the oxygen reduction reaction. This activity has been shown to be dependent on the size of the supported electrocatalyst nanoparticles. In this thesis the effects of Au nanoparticle size are explored for the oxygen reduction, ethanol oxidation and carbon monoxide oxidation reactions (Chapter four). The results show the oxygen reduction and ethanol oxidation reactions were favoured using larger particles, 6 nm in diameter, whilst the CO oxidation reaction was more facile on smaller particles, 3 nm in diameter. The effects of size are attributed to the size dependent strength of the Au-O (H) bond. Modified Au nanoparticles, in which the Au serves as a core for a Pt or Pd shell have also been of recent interest, as Au has been less expensive than Pt. These core-shell electrocatalysts thus affect both cost and activity advantages as the underlying Au core affect the properties of the shell. In this thesis the effects of the particle size of the Au core on the activity of Pt or Pd shells have been investigated (Chapter five). The results show that the oxygen reduction reaction is well again more facile when the core size is larger, whilst the ethanol oxidation reaction now is favoured with the small Au core size. The coverage of Pt or Pd on the Au core was also found to be dependent on the particle size, with smaller particles being covered by thinner shells. Thus, the size dependence of the oxygen reduction activity is once again attributed to O (H) coverage and bond strength, whilst the ethanol oxidation is attributed to either an electronic perturbation of the Pt or Pd by the Au core of an ensemble effect.

Download or read book Addition of Platinum to Palladium cobalt Nanoalloy Catalyst by Direct Alloying and Galvanic Displacement written by Brent Wise and published by . This book was released on 2010 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct methanol fuel cells (DMFC) are being investigated as a portable energy conversion device for military and commercial applications. DMFCs offer the potential to efficiently extract electricity from a dense liquid fuel. However, improvements in materials properties and lowering the cost of the electrocatalysts used in a DMFC are necessary for commercialization of the technology. The cathode electrocatalyst is a critical issue in DMFC because the state-of-the-art catalyst, platinum, is very expensive and rare, and its performance is diminished by methanol that crosses over from the anode to the cathode through the Nafion membrane. This thesis investigates the addition of platinum to a palladium-cobalt nanoalloy electrocatalyst supported on carbon black in order to improve catalyst activity for the oxygen reduction reaction (ORR) and catalyst stability against dissolution in acidic environment without significantly reducing the methanol-tolerance of the catalyst. Platinum was added to the palladium-cobalt nanoalloy catalyst using two synthesis methods. In the first method, platinum was directly alloyed with palladium and cobalt using a polyol reduction method, followed by heat treatment in a reducing atmosphere to form catalysts with 11 and 22 atom % platinum. In the second method, platinum was added to a palladium-cobalt alloy by galvanic displacement reaction to form catalysts with 10 and 22 atom % platinum. The palladium cobalt alloy was synthesized using a polyol method, followed by heat treatment in a reducing atmosphere to alloy the nanoparticles before the Pt displacement. It was found that both methods significantly improve catalyst activity and stability, with the displaced catalysts showing a higher activity than the corresponding alloy catalyst. However the alloy catalysts showed similar resistance to dissolution as the displaced catalysts, and the alloyed catalysts were more tolerant to methanol. The displaced catalyst with 22 atom % platinum (8 wt. % Pt overall) performed similar to a 20 wt. % commercial platinum catalyst in both RDE and single cell DMFC tests. The 10 and 22 atom % Pt displaced catalysts and 22 atom % Pt alloyed all showed higher Pt mass specific activities than a commercial Pt catalyst.

Download or read book Spontaneous Incorporation of Gold in Palladium based Ternary Nanoparticles Makes Durable Electrocatalysts for Oxygen Reduction Reaction written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Replacing platinum by a less precious metal such as palladium, is highly desirable for lowering the cost of fuel-cell electrocatalysts. However, the instability of palladium in the harsh environment of fuel-cell cathodes renders its commercial future bleak. Here we show that by incorporating trace amounts of gold in palladium-based ternary (Pd6CoCu) nanocatalysts, the durability of the catalysts improves markedly. Using aberration-corrected analytical transmission electron microscopy in conjunction with synchrotron X-ray absorption spectroscopy, we show that gold not only galvanically replaces cobalt and copper on the surface, but also penetrates through the Pd-Co-Cu lattice and distributes uniformly within the particles. The uniform incorporation of Au provides a stability boost to the entire host particle, from the surface to the interior. The spontaneous replacement method we have developed is scalable and commercially viable. This work may provide new insight for the large-scale production of non-platinum electrocatalysts for fuel-cell applications.

Download or read book Platinum coated Non noble Metal noble Metal Core shell Electrocatalysts written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Core-shell particles encapsulated by a thin film of a catalytically active metal are described. The particles are preferably nanoparticles comprising a non-noble core with a noble metal shell which preferably do not include Pt. The non-noble metal-noble metal core-shell nanoparticles are encapsulated by a catalytically active metal which is preferably Pt. The core-shell nanoparticles are preferably formed by prolonged elevated-temperature annealing of nanoparticle alloys in an inert environment. This causes the noble metal component to surface segregate and form an atomically thin shell. The Pt overlayer is formed by a process involving the underpotential deposition of a monolayer of a non-noble metal followed by immersion in a solution comprising a Pt salt. A thin Pt layer forms via the galvanic displacement of non-noble surface atoms by more noble Pt atoms in the salt. The overall process is a robust and cost-efficient method for forming Pt-coated non-noble metal-noble metal core-shell nanoparticles.

Download or read book Engineering Platinum Alloy Electrocatalysts in Nanoscale for PEMFC Application written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fuel cells are expected to be a key next-generation energy source used for vehicles and homes, offering high energy conversion efficiency and minimal pollutant emissions. However, due to large overpotentials on anode and cathode, the efficiency is still much lower than theoretically predicted. During the past decades, considerable efforts have been made to investigate synergy effect of platinum alloyed with base metals. But, engineering the alloy particles in nanoscale has been a challenge. Most important challenges in developing nanostructured materials are the abilities to control size, monodispersity, microcomposition, and even morphology or self-assembly capability, so called Nanomaterials-by-Design, which requires interdisciplinary collaborations among computational modeling, chemical synthesis, nanoscale characterization as well as manufacturing processing. Electrocatalysts, particularly fuel cell catalysts, are dramatically different from heterogeneous catalysts because the surface area in micropores cannot be electrochemically controlled on the same time scale as more transport accessible surfaces. Therefore, electrocatalytic architectures need minimal microporous surface area while maximizing surfaces accessible through mesopores or macropores, and to "pin" the most active, highest performance physicochemical state of the materials even when exposed to thermodynamic forces, which would otherwise drive restructuring, crystallization, or densification of the nanoscale materials. In this presentation, results of engineering nanoscale platinum alloy particles down to 2 ~ 4 nm will be discussed. Based on nature of alloyed base metals, various synthesis technologies have been studied and developed to achieve capabilities of controlling particle size and particle microcomposition, namely, core-shell synthesis, microemulsion technique, thermal decomposition process, surface organometallic chemical method, etc. The results show that by careful engineering the particle size and microcomposition in nanoscale, it is able to achieve superior electrocatalytic activities comparing with traditional preparative methods. Examples to be discussed are high surface area carbon supported Pt, PtM binary, and PtMN ternary alloys, their synthesis processes, characterizations and electrocatalytic activities towards molecular oxygen reduction.

Download or read book Inorganic Nanoparticles written by Claudia Altavilla and published by CRC Press. This book was released on 2017-12-19 with total page 601 pages. Available in PDF, EPUB and Kindle. Book excerpt: Among the various nanomaterials, inorganic nanoparticles are extremely important in modern technologies. They can be easily and cheaply synthesized and mass produced, and for this reason, they can also be more readily integrated into applications. Inorganic Nanoparticles: Synthesis, Applications, and Perspectives presents an overview of these special materials and explores the myriad ways in which they are used. It addresses a wide range of topics, including: Application of nanoparticles in magnetic storage media Use of metal and oxide nanoparticles to improve performance of oxide thin films as conducting media in commercial gas and vapor sensors Advances in semiconductors for light-emitting devices and other areas related to the energy sector, such as solar energy and energy storage devices (fuel cells, rechargeable batteries, etc.) The expanding role of nanosized particles in the field of catalysis, art conservation, and biomedicine The book’s contributors address the growing global interest in the application of inorganic nanoparticles in various technological sectors. Discussing advances in materials, device fabrication, and large-scale production—all of which are urgently required to reduce global energy demands—they cover innovations in areas such as solid-state lighting, detailing how it still offers higher efficiency but higher costs, compared to conventional lighting. They also address the impact of nanotechnology in the biomedical field, focusing on topics such as quantum dots for bioimaging, nanoparticle-based cancer therapy, drug delivery, antibacterial agents, and more. Fills the informational gap on the wide range of applications for inorganic nanoparticles in areas including biomedicine, electronics, storage media, conservation of cultural heritage, optics, textiles, and cosmetics Assembling work from an array of experts at the top of their respective fields, this book delivers a useful analysis of the vast scope of existing and potential applications for inorganic nanoparticles. Versatile as either a professional research resource or textbook, this effective tool elucidates fundamentals and current advances associated with design, characterization, and application development of this promising and ever-evolving device.

Download or read book Palladium Platinum Nanoparticles written by Simon Tymen and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The high price of platinum currently employed as catalyst for the oxygen reduction reaction in fuel cells represents an obstacle for a widespread usage of these cells. The development of bimetallic particles, reducing the quantity of platinum is a promising solution to increase the viability of the cells and to reduce their price. In this doctoral thesis, palladium was used as a second metal to synthesize bimetallic particles with easy methods. The role of bromide on the properties and performances of the palladium-platinum clusters with a nanoflowers structure was investigated (Chapter 2) and the effect of the time of synthesis on particles prepared by galvanic replacement was analyzed (Chapters 3 and 4). In the end, the formation/dissolution of oxide at the surface of core-shell palladium-platinum nanoparticles was examined (Chapter 4). ...

Download or read book Synthesis of Palladium and Palladium copper Nanostructures as Electrocatalysts written by Haibin Wu and published by . This book was released on 2015 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pd and its alloys are alternatives of Pt as promising catalysts and electrocatalysts for many reactions. Size controlled synthesis of nanoparticles remains a major research subject, since smaller size particles show better catalytic performance. In this work, we developed a modified chemical wet method to prepare Pd and Pd-Cu nanostructures with uniform small size. Different sizes and shapes of Pd nanostructures were successfully synthesized by using the two reducing agents (i.e., L-ascorbyl-6-palmitate or phenylphosphinic acid). The reducing agents play a role to control the final morphologies and sizes of particles. The use of L-ascorbyl-6-palmitate favors to form irregular branch shapes or rods; in contrast, the use of phenylphosphinic acid tends to form spherical nanoparticles. Furthermore, phenylphosphinic acid can assist with size control of Pd particles. Co-reducing Pd and Cu precursors can obtain Pd-Cu nanostructures with different sizes and shapes. The growth mechanism is followed the deposition of Cu on Pd seeds which are reduced prior to Cu. Similar to pure Pd synthesis, phenylphosphinic acid reduced the precursors to form small uniform spherical particles compared to L-ascorbyl-6-palmitate. It was also found that the composition could also be tuned by using different reducing agents. The catalytic activity of Pd and Pd-Cu nanostructures for ethanol oxidation reaction (EOR) has been tested in basic solution for alkaline fuel cell applications. The specific areas of these Pd and Pd-Cu are much higher than those reported previously. It was found that both Pd and Pd-Cu nanostructures exhibited enhanced catalytic activities and to some extent resisted CO-like intermediates poisoning. Most catalysts had enhanced current densities after 500 cycle scan, indicating enhanced stability of those catalysts.

Download or read book Well defined Nanoparticle Electrocatalysts for the Carbon Dioxide and Oxygen Reduction Reactions written by Jamie Allyce Trindell and published by . This book was released on 2020 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt: The lack of structurally diverse electrocatalysts having high activity and controlled selectivity has limited progress in the development of technologically relevant electrochemical transformations. The key to making progress is the synergy between experiment and theory, and particularly experimental model systems against which the efficacy of theory can be benchmarked. The goal of this dissertation is to address the persisting experimental limitations that erode the fruitfulness of this union between theory and electrocatalysis. To this end, well-defined nanoparticle electrocatalysts enabling experimental validation of theoretical predictions are reported here for the carbon dioxide and oxygen reduction reactions, respectively. First, we describe the use of ex-situ scanning transmission electron microscopy (STEM) to analyze the growth of gold nanoparticles (AuNPs) during electrocatalytic CO2 reduction (Chapter 2). Relative to citrate-capped AuNPs, dendrimer-encapsulated Au NPs (Au DENs) demonstrate significantly improved structural stability during CO2 electrolysis. This work highlights the importance of performing catalyst characterization both before and after (and, ideally, during) electrochemical measurements to identify the most accurate computational models for a given electrocatalytic system. Next, we focus on Pd-based nanoalloy catalysts for the oxygen reduction reaction (ORR). Chapter 3 details the experimental verification of PdIr nanoalloy catalysts predicted to have worse catalytic activity towards the oxygen reduction reaction (ORR) than their monometallic counterparts. Specifically, alloying Ir with Pd systematically decreases the ORR activity relative to monometallic Pd NPs. The findings of this study are significant because verifying the ability of theoretical predictions to both rule-in and rule-out potential catalysts holds the key for allowing theory to guide catalyst design. Chapter 4 reports experimental evidence of composition-dependent modulation of O-binding energies on Au [subscript x] Pd [subscript (300-x)] DENs. Specifically, electrochemical characterization identifies unique active sites on AuPd nanoalloys. The concept of surface ensembles, or the presence of unique active sites on the surface of nanoalloys, is a useful concept in theoretical models that is lacking in experimental verification. Altogether, the work described in this dissertation aims to continue to close the gap between theory and experiment in the field of electrocatalysis