Download or read book Recent Advances in Developing Platinum Monolayer Electrocatalysts for the O2 Reduction Reaction written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: For Pt, the best single-element catalyst for many reactions, the question of content and loading is exceedingly important because of its price and availability. Using platinum as a fuel-cell catalyst in automotive applications will cause an unquantifiable increase in the demand for this metal. This big obstacle for using fuel cells in electric cars must be solved by decreasing the content of Pt, which is a great challenge of electrocatalysis Over the last several years we inaugurated a new class of electrocatalysts for the oxygen reduction reaction (ORR) based on a monolayer of Pt deposited on metal or alloy carbon-supported nanoparticles. The possibility of decreasing the Pt content in the ORR catalysts down to a monolayer level has a considerable importance because this reaction requires high loadings due to its slow kinetics. The Pt-monolayer approach has several unique features and some of them are: high Pt utilization, enhanced (or decreased) activity, enhanced stability, and direct activity correlations. The synthesis of Pt monolayer (ML) electrocatalysts was facilitated by our new synthesis method which allowed us to deposit a monolayer of Pt on various metals, or alloy nanoparticles [1, 2] for the cathode electrocatalyst. In this synthesis approach Pt is laid down by the galvanically displacing a Cu monolayer, which was deposited at underpotentials in a monolayer-limited reaction on appropriate metal substrate, with Pt after immersing the electrode in a K2PtCl4 solution.

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 Platinum Monolayer Electrocatalysts for Oxygen Reduction in Fuel Cells written by Junliang Zhang and published by . This book was released on 2005 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Design and Development of Nanostructured Thin Films written by Antonella Macagnano and published by MDPI. This book was released on 2020-05-13 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to their unique size-dependent physicochemical properties, nanostructured thin films are used in a wide range of applications from smart coating and drug delivery to electrocatalysis and highly-sensitive sensors. Depending on the targeted application and the deposition technique, these materials have been designed and developed by tuning their atomic-molecular 2D- and/or 3D-aggregation, thickness, crystallinity, and porosity, having effects on their optical, mechanical, catalytic, and conductive properties. Several open questions remain about the impact of nanomaterial production and use on environment and health. Many efforts are currently being made not only to prevent nanotechnologies and nanomaterials from contributing to environmental pollution but also to design nanomaterials to support, control, and protect the environment. This Special Issue aims to cover the recent advances in designing nanostructured films focusing on environmental issues related to their fabrication processes (e.g., low power and low cost technologies, the use of environmentally friendly solvents), their precursors (e.g., waste-recycled, bio-based, biodegradable, and natural materials), their applications (e.g., controlled release of chemicals, mimicking of natural processes, and clean energy conversion and storage), and their use in monitoring environment pollution (e.g., sensors optically- or electrically-sensitive to pollutants)

Download or read book Electrocatalysts for Low Temperature Fuel Cells written by Thandavarayan Maiyalagan and published by John Wiley & Sons. This book was released on 2017-05-08 with total page 618 pages. Available in PDF, EPUB and Kindle. Book excerpt: Meeting the need for a text on solutions to conditions which have so far been a drawback for this important and trend-setting technology, this monograph places special emphasis on novel, alternative catalysts of low temperature fuel cells. Comprehensive in its coverage, the text discusses not only the electrochemical, mechanistic, and material scientific background, but also provides extensive chapters on the design and fabrication of electrocatalysts. A valuable resource aimed at multidisciplinary audiences in the fields of academia and industry.

Download or read book Development of Platinum free Electrocatalysts for Oxygen Reduction Reaction in the Proton Exchange Membrane Fuel Cell written by Lingyun Liu (Ph. D.) and published by . This book was released on 2006 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Rotating Electrode Methods and Oxygen Reduction Electrocatalysts written by Wei Xing and published by Elsevier. This book was released on 2014-03-26 with total page 323 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rotating Electrode Methods and Oxygen Reduction Electrocatalysts provides the latest information and methodologies of rotating disk electrode and rotating ring-disk electrode (RDE/RRDE) and oxygen reduction reaction (ORR). It is an ideal reference for undergraduate and graduate students, scientists, and engineers who work in the areas of energy, electrochemistry science and technology, fuel cells, and other electrochemical systems. Presents a comprehensive description, from fundamentals to applications, of catalyzed oxygen reduction reaction and its mechanisms Portrays a complete description of the RDE (Rotating Disc Electrode)/RRDE (Rotating Ring-Disc Electrode) techniques and their use in evaluating ORR (Oxygen Reduction Reaction) catalysts Provides working examples along with figures, tables, photos and a comprehensive list of references to help understanding of the principles involved

Download or read book Electrocatalysts for Fuel Cells and Hydrogen Evolution written by Abhijit Ray and published by BoD – Books on Demand. This book was released on 2018-12-05 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book starts with a theoretical understanding of electrocatalysis in the framework of density functional theory followed by a vivid review of oxygen reduction reactions. A special emphasis has been placed on electrocatalysts for a proton-exchange membrane-based fuel cell where graphene with noble metal dispersion plays a significant role in electron transfer at thermodynamically favourable conditions. The latter part of the book deals with two 2D materials with high economic viability and process ability and MoS2 and WS2 for their prospects in water-splitting from renewable energy.

Download or read book Synchrotron Based In Situ Characterization of Carbon Supported Platinum and Platinum Monolayer Electrocatalysts written by and published by . This book was released on 2015 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding oxidation/dissolution mechanisms of Pt is critical in designing durable catalysts for the oxygen reduction reaction (ORR), but exact mechanisms remain unclear. Our present work explores the oxidation/dissolution of Pt and Pt monolayer (ML) electrocatalysts over a wide range of applied potentials using cells that facilitate in situ measurements by combining X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) measurements. Furthermore, the X-ray absorption near edge structure (XANES) measurement demonstrated that Pt nanoparticle surfaces were oxidized from metallic Pt to [alpha]-PtO2-type oxide during the potential sweep from 0.41 to 1.5 V, and the transition state of O or OH adsorption on Pt and the onset of the place exchange process were revealed by the delta mu ([Delta][mu]) method. Only the top layers of Pt nanoparticles were oxidized, while the inner Pt atoms remained intact. At a higher potential over 1.9 V, [alpha]-PtO2-type surface oxides dissolve due to local acidification caused by the oxygen evolution reaction and carbon corrosion. Pt oxidation of PtML on the Pd nanoparticle electrocatalyst is considerably hampered compared with the Pt/C catalyst, presumably because preferential Pd oxidation proceeds at the defects in Pt MLs up to 0.91 V and through O penetrated through the Pt MLs by the place exchange process above 1.11 V.

Download or read book Investigation of New Pt Monolayer Electrocatalysts for O2 Reduction written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Recent Advances in the Kinetics of Oxygen Reduction written by and published by . This book was released on 1996 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: Oxygen reduction is considered an important electrocatalytic reaction; the most notable need remains improvement of the catalytic activity of existing metal electrocatalysts and development of new ones. A review is given of new advances in the understanding of reaction kinetics and improvements of the electrocatalytic properties of some surfaces, with focus on recent studies of relationship of the surface properties to its activity and reaction kinetics. The urgent need is to improve catalytic activity of Pt and synthesize new, possibly non- noble metal catalysts. New experimental techniques for obtaining new level of information include various {ital in situ} spectroscopies and scanning probes, some involving synchrotron radiation. 138 refs, 18 figs, 2 tabs.

Download or read book Polymer Electrolyte Fuel Cell Durability written by Felix N. Büchi and published by Springer Science & Business Media. This book was released on 2009-02-08 with total page 489 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers a significant number of R&D projects, performed mostly after 2000, devoted to the understanding and prevention of performance degradation processes in polymer electrolyte fuel cells (PEFCs). The extent and severity of performance degradation processes in PEFCs were recognized rather gradually. Indeed, the recognition overlapped with a significant number of industrial dem- strations of fuel cell powered vehicles, which would suggest a degree of technology maturity beyond the resaolution of fundamental failure mechanisms. An intriguing question, therefore, is why has there been this apparent delay in addressing fun- mental performance stability requirements. The apparent answer is that testing of the power system under fully realistic operation conditions was one prerequisite for revealing the nature and extent of some key modes of PEFC stack failure. Such modes of failure were not exposed to a similar degree, or not at all, in earlier tests of PEFC stacks which were not performed under fully relevant conditions, parti- larly such tests which did not include multiple on–off and/or high power–low power cycles typical for transportation and mobile power applications of PEFCs. Long-term testing of PEFCs reported in the early 1990s by both Los Alamos National Laboratory and Ballard Power was performed under conditions of c- stant cell voltage, typically near the maximum power point of the PEFC.

Download or read book Developing New Catalysts for Electrochemical Energy Conversion written by Ariel Jackson and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Reliance on fossil fuels as society's primary energy source has detrimental effects on climate, air quality and public health, economic competitiveness, and geo-political stability. A rapid transition to renewable energy is required and hydrogen fuel cells offer a promising pathway, particularly in the transportation sector. Despite significant progress over the past two decades, large scale commercialization of fuel cell automobiles has not been realized. Several companies have been leasing prototypes and claim that production models will go on sale for the first time in 2015, however the scarcity and cost of platinum--required to catalyze the electrochemical reactions in the fuel cell--remains the primary impediment to full implementation of fuel cell powered vehicles. Most of the Pt in a fuel cell is used on the oxygen electrode (cathode) to catalyze the sluggish oxygen reduction reaction (ORR). The primary pathway to reducing the Pt loading is to develop catalysts that are more active than Pt. In this dissertation, I will focus on the development of a new type of ORR electrocatalyst, ruthenium-core platinum-shell (Ru@Pt) nanoparticles. Theoretical understanding of the ORR mechanisms has improved dramatically in the last decade, demonstrating that the key parameter for catalytic activity is the binding strength of oxygen to the catalyst surface. In a theory-experiment collaboration, density functional theory (DFT) calculations showed that the oxygen binding strength to a Ru@Pt surface was more optimal (slightly weaker) than pure Pt. Using the DFT calculations to guide the catalyst design, we prepared Ru@Pt nanoparticles using a liquid phase synthesis. We confirmed that the nanoparticles have the intended Ru-core Pt-shell structure using a combination of transmission electron microscopy (TEM), scanning transmission electron microscopy-energy dispersive spectroscopy (STEM-EDS), and Z-contrast annular dark field-scanning transmission electron microscopy (ADF-STEM). The activity of the catalysts was tested using rotating disk electrochemistry, and a greater than two fold improvement was exhibited in the specific (per reaction-site) activity of Ru@Pt over state-of-the-art commercial Pt nanoparticles. We devised a new electrochemical conditioning treatment, tailored to the Ru@Pt catalyst, which involves cycling the nanoparticles between highly oxidizing and reducing potentials. The conditioning further improved the activity of Ru@Pt by a factor of two. While unprotected Ru nanoparticles are unstable at the oxidative potentials encountered in the conditioning treatment, analysis with STEM-EDS shows that the Pt-shell protects the Ru-core, mitigating Ru dissolution. Optimization of the Ru@Pt nanoparticle structure led to a seven fold enhancement in mass activity (activity per gram of Pt) over the first generation Ru@Pt catalysts. The effect of Pt content in the synthesis was investigated and the particle size, surface area, and activity were found to vary with Pt composition, with the mass activity maximized at a Pt:Ru ratio equal to one. Optimized Ru@Pt exhibited a mass activity of 0.497 A mg-1Pt at 0.9 V vs. RHE, exceeding the Department of Energy 2020 target. The Ru@Pt catalyst was tested for durability and retained 85% of its starting mass activity after 30,000 stability cycles, compared to commercial Pt nanoparticles which had a lower initial mass activity and only retained 62%. The newly developed Ru@Pt catalysts demonstrate impressive activity and stability and are a promising platform for reducing Pt use in fuel cells.

Download or read book Renewable Polymers and Polymer Metal Oxide Composites written by Sajjad Haider and published by Elsevier. This book was released on 2022-03-17 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt: Renewable Polymers and Polymer-Metal Oxide Composites: Synthesis, Properties, and Applications serves as a reference on the key concepts of the advances of polymer-oxide composites. The book reviews knowledge on polymer-composite theory, properties, structure, synthesis, and their characterization and applications. There is an emphasis on coupling metal oxides with polymers from renewable sources. Also, the latest advances in the relationship between the microstructure of the composites and the resulting improvement of the material’s properties and performance are covered. The applications addressed include desalination, tissue engineering, energy storage, hybrid energy systems, food, and agriculture. This book is suitable for early-career researchers in academia and R&D in industry who are working in the disciplines of materials science, engineering, chemistry and physics. Provides basic principles, theory and synthetic methods of composite materials, polymer composites and metal oxides Reviews the latest advances in polymer-oxide-based applications in medicine, water treatment, energy and sensing Discusses materials from renewable resources, including lifecycle assessment, economic aspects and potential application in tissue engineering, photovoltaics and food packaging

Download or read book Reactivity and Stability of Platinum and Platinum Alloy Catalysts Toward the Oxygen Reduction Reaction written by Sergio Rafael Calvo and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Density functional theory (DFT) is used to study the reactivity of Pt and Pt-M (M: Pd, Co, Ni, V, and Rh) alloy catalysts towards the oxygen reduction reaction (ORR) as a function of the alloy overall composition and surface atomic distribution and compared to that on pure Pt surfaces. Reactivity is evaluated on the basis of the adsorption strength of oxygenated compounds which are intermediate species of the four-electron oxygen reduction reaction, separating the effect of the first electron-proton transfer from that of the three last electron-proton transfer steps. It is found that most homogeneous distribution PtxM catalysts thermodynamically favor the dissociation of adsorbed OOH in comparison with pure Platinum and adsorb strongly O and OH due to the strong oxyphilicity of the M elements. On the other hand, in all cases skin Platinum surfaces catalysts do not favor the dissociation of adsorbed OOH and do favor the reduction of M-O and M-OH with respect to Platinum. Considering the overall pathway of the reactions to catalyze the ORR most of the skin Platinum monolayer catalysts provide more negative free energy changes and should behave at least in a similar way than Platinum in following order: Pt3V (skin Pt)> Pt3Co (skin Pt)> Pt3Ni (skin Pt)> Pt> PtPd (skin)> Pt4Rh (skin Pt)> PtPd3 (skin). In all cases, the reactivity is shown to be not only sensitive to the overall composition of the catalyst, but most importantly to the surface atomic distribution. Proposed electrochemical dissolution reactions of the catalyst atoms are also analyzed for the ORR catalysts, by computing the free energy changes of Platinum and bimetallic Pt-X (X: Co, Pd, Ni, and Rh) catalysts. It is found that Platinum is thermodynamically more stable than Pt-alloys in Pt3Co, Pt3Pd, Pt3Ni and Pt4Rh.

Download or read book PEM Fuel Cell Electrocatalysts and Catalyst Layers written by Jiujun Zhang and published by Springer Science & Business Media. This book was released on 2008-08-26 with total page 1147 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proton exchange membrane (PEM) fuel cells are promising clean energy converting devices with high efficiency and low to zero emissions. Such power sources can be used in transportation, stationary, portable and micro power applications. The key components of these fuel cells are catalysts and catalyst layers. “PEM Fuel Cell Electrocatalysts and Catalyst Layers” provides a comprehensive, in-depth survey of the field, presented by internationally renowned fuel cell scientists. The opening chapters introduce the fundamentals of electrochemical theory and fuel cell catalysis. Later chapters investigate the synthesis, characterization, and activity validation of PEM fuel cell catalysts. Further chapters describe in detail the integration of the electrocatalyst/catalyst layers into the fuel cell, and their performance validation. Researchers and engineers in the fuel cell industry will find this book a valuable resource, as will students of electrochemical engineering and catalyst synthesis.

Download or read book Nanostructured Oxygen Reduction Catalyst Designs to Reduce the Platinum Dependency of Polymer Electrolyte Fuel Cells written by Drew Christopher Higgins and published by . This book was released on 2015 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer electrolyte fuel cells (PEFCs) are electrochemical devices that efficiently convert hydrogen and oxygen into electricity and water. Their clean point of operation emissions and fast refueling times have resulted in PEFCs being highly touted as integral components of sustainable energy infrastructures, most notably in the transportation sector. The issues associated with hydrogen production and distribution aside, the commercial viability of PEFCs is still hindered by the high cost and inadequate long term operational stability. A main contributor towards both of these issues is the platinum-based electrocatalysts used at the cathode to facilitate the inherently sluggish oxygen reduction reaction (ORR). These expensive precious metal catalysts comprise almost half of the overall PEFC stack cost, and undergo degradation under the cathode environment that is very corrosive due to the acidic and potentiodynamic conditions. There is therefore ample room for cost reduction if reduced platinum ORR catalysts can be developed with sufficient activity and durability to meet the technical targets set for the use of PEFCs in automobiles. In this work, two classes of nanostructured catalysts are investigated. The first is high activity platinum or platinum alloy materials with the objective of surpassing the activity of conventional catalysts on a precious metal basis to achieve cost reductions. The second is non-platinum group metal (non-PGM) catalysts, that while intrinsically less active than platinum, can still provide high power output at moderate operating voltages, such as those encountered during automobile operation. These two catalyst technologies are developed and delivered with the ultimate objective of integrating them together into platinum/non-PGM hybrid electrodes to provide excellent PEFC performance with a reduced platinum dependency. In Chapter 4, titanium nitride - carbon nanotube (TiN-CNT) core-shell nanocomposites developed by a simplistic two step fabrication procedure are reported. These materials are physicochemically characterized by a variety of microscopy and spectroscopy techniques and used as platinum nanoparticle elelectrocatalyst supports (Pt/TiN-CNT) for the ORR. Through half-cell electrochemical testing in acidic electrolyte, improved ORR activity was demonstrated for Pt/TiN-CNTs compared with state of the art commercial Pt/C. The one-dimensional morphology of the TiN-CNT supports is also conducive for integration into highly porous electrode structures with excellent interconnectivity to ensure reactant access and electronic conductivity throughout the catalyst layer, respectively. The long term stability of this catalyst however remains questionable, likely due to oxidation of the titanium nitride surface that results in a thin passivating layer. It is becoming increasingly evident that corrosion of platinum nanoparticle supports is inevitable during fuel cell operation. To overcome this, a focus was then placed on the development of supportless nanostructured platinum catalyst designs. Platinum cobalt nanowires (Pt-Co-NWs) were prepared by simplistic, template free microwave-irradiation process as discussed in Chapter 5. Using cobalt as an alloying element was undertaken owing to the documented ability of this transition metal to modulate the adsorptive properties of platinum and induce increased ORR activity. The one-dimensional anisotropic nanostructure can also provide increased platinum stability owing to the reduced surface energies in comparison to zero dimensional nanoparticles. The Pt-Co-NWs displayed promising ORR activity a through half-cell testing in 0.1 M HClO4. Most notably, using harsh accelerated durability testing (ADT) that consisted of 1,000 electrochemical potential cycles from 0 to 1.5 V vs. RHE at 50 °C, the Pt-Co-NWs maintained the majority of their ORR activity, highlighting exemplary stability. While simple, the drawback of this synthesis approach is that it did not allow for nanowire diameters that were below 40 nm. This resulted in inaccessible platinum atoms within the nanowire cores, highlighting the fact that further improved ORR activity on a platinum mass basis could be achieved with reduced diameters. To accomplish this, the electrospinning approach was used to prepare PtCoNWs (please note the nomenclature distinction). Through investigations in which synthesis parameters were systematically investigated, electrospinning was found to provide a versatile platform for the synthesis of nanowires with tunable diameters and atomic compositions. PtCoNWs with a near unity stoichiometric ratio, excellent atomic distribution and an average diameter of 28 nm were evaluated for ORR activity. Over a four-fold enhancement in Pt mass-based activity at an electrode potential of 0.9 V vs RHE is obtained in comparison to pure platinum nanowires, highlighting the beneficial impact of the alloying structure. A near 7-fold specific activity increase is also observed in comparison to commercial Pt/C catalyst, along with improved electrochemically active surface area retention through repetitive (1,000) potential cycles. Electrospinning is thereby an attractive approach to prepare morphology and composition controlled PtCoNWs that could potentially one day replace conventional nanoparticle catalysts. With the development of PtCoNWs established, developing non-PGM catalysts that can be hybridized with the high activity platinum-based catalysts was required. In Chapter 7, single crystal cobalt disulfide (CoS2) octahedral nanoparticles supported on graphene/carbon nanotube composites were prepared as ORR catalysts. During the simplistic, one-pot solvothermal synthesis, the nanostructured carbon supports were also simultaneously doped with nitrogen and sulfur. Time dependent studies elucidated the growth process of the {111} facet encased octahedra that could only be prepared when carbon support materials were incorporated into the reaction mixture. The impact of carbon support on ORR activity was clear, with the graphene/carbon nanotube composite supported CoS2 octahedra (CoS2-CG) outperforming CoS2 supported on just graphene or carbon nanotubes. Additionally, CoS2-CG provided an on-set potential (0.78 V vs. RHE) and half-wave potential (0.66 V vs. RHE) that was 60 mV and 150 mV higher than the CoS2 particle agglomerates formed when no carbon support was included during catalyst preparation. By combining the synergistic properties of the graphene/carbon nanotube composite and unique shape controlled single crystal CoS2 nanoparticles, CoS2-CG comprises the highest activity non-precious metal transition metal chalcogenide reported to date, and is presented as an emerging catalyst for the ORR in fuel cells. Chapter 8 provides a summary of the conclusions of this body of work, along with strategies that can be employed to capitalize on the scientific advancements made through this thesis. The delivery of PtCoNWs and CoS2-CG that can be reliably prepared by simple techniques provides the crucial first step towards the development of platinum/non-PGM hybrid electrodes. Future projects should focus on the integration of these two catalysts into new electrode arrangements in an attempt to exploit their individual properties. Through this approach, it is hypothesized that synergistic coupling of these two catalysts can lead to PEFC systems with reduced activation losses from the PtCoNWs, along with CoS2-CG providing increased maximum power densities at lower cell voltages, all at reduced platinum contents in comparison to state of the art PEFC cathodes.