Download or read book Advanced Non precious Metal Catalyst for Oxygen Reduction Reaction in Polymer Electrolyte Membrane Fuel Cells written by Gaopeng Jiang and published by . This book was released on 2018 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: To address the global energy and environmental challenges, the polymer electrolyte membrane fuel cell (PEMFC) is proposed and developed as one of the most promising power source candidates for various applications including electric vehicles, stationary power stations and portable devices due to its high efficiency and low emissions. However, the intrinsically sluggish reaction at the cathode, namely the oxygen reduction reaction (ORR), hinders the large-scale commercialization of the PEMFC as expensive and scarce platinum-based catalysts are used to accelerate this reaction. In order to reduce the cost of PEMFC, non-precious metal catalyst (NPMC) towards ORR has been developed and already brought itself from a pure scientific curiosity to a practically viable option for some commercial applications. In this work, two classes of low-cost NPMCs are investigated. One class is composed of high temperature treated transition metal-nitrogen-carbon M-N-C (M=Fe, Co) complex catalyst, especially iron-nitrogen-carbon complex (Fe-N-C) catalyst. These materials can demonstrate decent ORR activity and durability and provide high power output at moderate operating voltages. The other class with an even lower cost is the metal-free catalyst, which omits the metal content from M-N-C catalysts completely. This type of catalyst demonstrates excellent durability, especially in the presence of species that can cause contamination (e.g. carbon monoxide) or species that can cross-over (e.g. methanol). These two classes of NPMCs are developed and delivered with the ultimate objective of achieving a significant cost reduction in PEMFC while maintaining excellent PEMFC performance and durability. Herein, the research in this thesis starts with novel N, S-co-doped Fe-N-C catalysts to meet the objective of obtaining a highly economical and efficient NPMC. The catalyst is fabricated via pyrolyzing the composite of in-situ polymerized novel N, S-co-containing precursor, polyrhodanine (PRh) onto the acid-treated carbon black via the initiation of FeCl3. The N, S-co-doped Fe-N-C catalyst is obtained after two heat-treatment steps with one acid-leaching step in between. The catalyst demonstrates excellent ORR activity, bearing a half-wave potential of 0.77 V vs RHE in the acidic electrolyte. It also shows an excellent H2-air PEMFC performance, ranking the obtained peak power density (386 mW cm-2 at 0.46 V) among the best reported NMPC catalyst in H2-air PEMFC in the world. The N, S-co-doped Fe-N-C catalyst tends to catalyze the oxygen reduction via four electron pathway according to its number of transferred electrons (>3.94) and low peroxide yield (

Download or read book Advanced Carbon Nanomaterials as Non precious Metal Catalysts for Fuel Cells written by Pouyan Zamani and published by . This book was released on 2017 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer electrolyte membrane fuel cells (PEMFCs) are electrochemical devices that efficiently convert hydrogen and oxygen into electricity and water. Their clean point of operation emissions and continuous operation have resulted in PEMFCs being highly touted as integral components of sustainable energy infrastructures, most notably in the transportation sector as a green alternative to the internal combustion engine. The issues associated with hydrogen production and distribution aside, the commercial viability of PEMFCs into the auto- motive sector is hindered by their high cost and inadequate long-term operational stability. The main factor behind both of these problems 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 PEMFC stack cost and tend to degrade in the cathode environment that is very corrosive due to the acidic and potentiodynamic conditions. The current cost targets for PEMFCs are unattainable unless the extensive reliance on this precious metal is alleviated. The cost reduction can ultimately be accomplished by developing alternative cathode catalysts for the ORR. Research on new platinum catalyst supports or nanostructured platinum alloys to increase ORR activity on a precious metal mass basis have been largely successful. This approach is not ideal, however, due to the volatile pricing and geopolitical instabilities that can likely affect the supply of platinum. For these reasons, the development of entirely non-precious metal catalysts (NPMCs) for the ORR is highly desirable. This is the objective of this thesis, as will be presented in the following sections.

Download or read book Improving Oxygen Reduction Reaction Catalysts for Polymer Electrolyte Membrane Fuel Cells written by Jarrid A. Wittkopf and published by . This book was released on 2017 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer electrolyte membrane fuel cells include proton exchange membrane fuel cells (PEMFCs) and hydroxide exchange membrane fuel cells (HEMFCs). PEMFCs use a proton conducting electrolyte, generating an acidic environment, while HEMFCs employ a hydroxide conducting electrolyte, providing a basic environment. For both types of fuel cells, the oxygen reduction reaction (ORR) at the cathode is sluggish and controls the fuel cell performance. Therefore, this thesis focuses on improving ORR catalyst activity and durability. ☐ PEMFCs, the more mature technology, have been commercially implemented in fuel cell cars like the Toyota Mirai and Honda Clarity. However, PEMFCs are expensive because they require a large amount of platinum (Pt) catalyst to overcome the ORR overpotential and the rapid catalyst degradation caused by the acidic operating environment. Current PEMFCs use Pt nanoparticles supported on amorphous carbon black as ORR catalysts. These catalysts have activity and durability concerns resulting from both the Pt nanoparticles and the amorphous carbon support. Strategies to improve catalyst activity and durability include generating a support-less catalyst, increasing the durability of the catalyst support, and switching to a basic environment. ☐ A transition to unsupported catalysts with an extended surface structure improves specific activity and durability and in turn, the cost-effectiveness of the entire fuel cell. Pt-coated copper nanowires (Pt/CuNW) exemplify these desirable catalytic traits. Improving this platform, post-synthetic processing is used to further enhance the ORR performance of the Pt/CuNW catalyst. Specifically, annealing followed by electrochemical dealloying increases activity by introducing geometric lattice tuning through Cu alloying. The resultant bimetallic PtCu-coated copper nanowire (PtCu/CuNW) catalyst yields ORR specific and mass activities of 2.65 mA cmPt-2 and 1.24 A mgPt-1, surpassing the respective DOE targets (SA and MA) of 0.72 mA cmPt-2 and 0.44 A mgPt-1. PtCu/CuNWs demonstrate enhanced durability over Pt nanoparticle catalysts by maintaining 64.1 % of its active surface area after undergoing 30,000 cycles of a potential cycling accelerated durability test (0.6 - 1.1 vs RHE). Post durability PtCu/CuNWs outperformed the DOE targets with a SA and MA of 1.50 mA cmPt-2 and 0.477 A mgPt-1 ☐ Alternately, increasing catalyst support durability through the introduction of a more durable carbon support has also been accomplished. Highly graphitic and cost-effective Cup-stacked carbon nanofiber supports have the potential to address the support durability concerns. Pt supported on carbon black (Vulcan XC-72) and cup-stacked carbon nanofibers as well as each carbon support alone underwent a high potential (1.4 V vs RHE) accelerated durability test in acidic and basic environments using rotating disk electrode techniques. It was shown that in all environments the cup-stacked carbon nanofiber support demonstrated higher durability and the catalysts tested in the basic environment had better overall stability compared to their acidic counterpart. ☐ HEMFCs have the potential for incorporating a wide variety of non-precious metal catalysts and promise to dramatically lower the fuel cell cost. One commercially available non-precious metal catalyst is Acta 4020. This carbon-based catalyst, containing 3.5 wt. % transition metals, when compared to state-of-the-art Pt/C catalysts shows comparable ORR performance and superior durability while exposed to a potential cycling (0.6 – 1.1 V vs RHE) accelerated durability test. Fuel cell testing also demonstrated the feasibility of incorporating this catalyst into the cathode electrode of a HEMFC.

Download or read book Non Noble Metal Fuel Cell Catalysts written by Zhongwei Chen and published by John Wiley & Sons. This book was released on 2014-04-03 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written and edited by top fuel cell catalyst scientists and engineers from both industry and academia, this is the first book to provide a complete overview of this hot topic. It covers the synthesis, characterization, activity validation and modeling of different non-noble metal electrocatalysts, as well as their integration into fuel cells and their performance validation, while also discussing those factors that will drive fuel cell commercialization. With its well-structured approach, this is a must-have for researchers working on the topic, and an equally valuable companion for newcomers to the field.

Download or read book Advanced Electrocatalysts for Low Temperature Fuel Cells written by Francisco Javier Rodríguez-Varela and published by Springer. This book was released on 2018-10-09 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces the reader to the state of the art in nanostructured anode and cathode electrocatalysts for low-temperature acid and alkaline fuel cells. It explores the electrocatalysis of anode (oxidation of organic molecules) and cathode (oxygen reduction) reactions. It also offers insights into metal-carbon interactions, correlating them with the catalytic activity of the electrochemical reactions. The book explores the electrocatalytic behaviour of materials based on noble metals and their alloys, as well as metal-metal oxides and metal-free nanostructures. It also discusses the surface and structural modification of carbon supports to enhance the catalytic activity of electrocatalysts for fuel-cell reactions.

Download or read book Development of Non precious Metal Catalysts for the Oxygen Reduction Reaction written by Melissa Ellen Kreider and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Eliminating greenhouse gas emissions to mitigate the effects of climate change is a global imperative. To achieve this goal, the world's dependence on fossil fuels must be ended and renewable energy technologies must be developed and deployed on a massive scale. The electrocatalytic oxygen reduction reaction (ORR) is an important limiting step in several promising technologies, including fuel cells, metal-air batteries, and the sustainable synthesis of hydrogen peroxide. Polymer electrolyte membrane fuel cells (PEMFCs) are a clean and efficient technology for converting chemical energy, e.g. in the form of hydrogen fuel, into electrical energy for transportation and backup power generation. The majority of the efficiency losses in a PEMFC are due to the sluggish kinetics of the ORR, requiring significant loadings of platinum-based catalysts at the cathode. The scarcity and high cost of platinum is therefore a limiting factor for the widespread development of PEMFC technologies. In this dissertation, we develop several low-cost, non-precious metal ORR catalysts for acidic and alkaline media, as well as techniques for understanding the relationship between performance and material properties. First, we investigate the performance of a thin film, carbon-free nickel nitride catalyst, finding substantial ORR activity in acidic and alkaline media. We identify significant surface oxidation with testing and air exposure. Utilizing electrochemical cycling and stability testing informed by Pourbaix diagrams, the role of surface oxidation in determining catalyst activity and stability is explored. This work demonstrates the importance of understanding material surface properties and stability. We next use a molybdenum (oxy)nitride thin film system to probe the role of structure and composition in ORR performance in acidic conditions. Using extensive materials characterization, the depth-dependent structure and composition of the films are determined, discovering the high O content in the bulk of films with a highly-defected structure. This bulk O content is found to be the strongest predictor of ORR activity. We use in situ characterization techniques to understand the material changes that occur during reaction, particularly those associated with potential-dependent catalytic behavior, finding that the catalyst surface undergoes distortion, amorphization, and O incorporation. We identify a potential window in which the intrinsic catalytic activity can be enhanced without the roughening or dissolution that lead to instability. This work demonstrates how ex situ and in situ techniques can be used to develop a rigorous understanding of a catalyst material, which can then be leveraged to optimize catalyst performance. Finally, we explore corrosion-resistant, conductive antimonates as a framework for enhancing the activity and stability of transition metal active sites. The antimonates are found to have superior intrinsic activity on a TM mass basis relative to the comparable oxides in alkaline electrolyte. Strategies for improving catalyst performance including electrode engineering and doping are investigated. Validating a theoretical prediction, a Mn-Cr antimonate solid solution is found to have enhanced mass activity compared to the pure Mn antimonate (on a TM basis). Further modifications of the antimonate framework are discussed, as well as strategies for materials discovery and development. In summary, this thesis addresses the challenge of PEMFC catalyst cost and performance through the discovery and development of non-precious metal ORR catalysts. Utilizing thorough materials and electrochemical characterization, we aim to develop fundamental understanding of these catalysts and strategies for improving their performance. For the ORR and beyond, this work demonstrates approaches to materials discovery and development that will be needed to advance and commercialize a wide variety of renewable energy technologies.

Download or read book Electrocatalysis in Fuel Cells written by Minhua Shao and published by Springer Science & Business Media. This book was released on 2013-04-08 with total page 748 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fuel cells are one of the most promising clean energy conversion devices that can solve the environmental and energy problems in our society. However, the high platinum loading of fuel cells - and thus their high cost - prevents their commercialization. Non- or low- platinum electrocatalysts are needed to lower the fuel cell cost. Electrocatalysis in Fuel Cells: A Non and Low Platinum Approach is a comprehensive book summarizing recent advances of electrocatalysis in oxygen reduction and alcohol oxidation, with a particular focus on non- and low-Pt electrocatalysts. All twenty four chapters were written by worldwide experts in their fields. The fundamentals and applications of novel electrocatalysts are discussed thoroughly in the book. The book is geared toward researchers in the field, postgraduate students and lecturers, and scientists and engineers at fuel cell and automotive companies. It can even be a reference book for those who are interested in this area.

Download or read book Nanostructured Non precious Metal Catalyst and Its Behavior in the Catalyst Layer in PEM Fuel Cells written by Ja-Yeon Choi and published by . This book was released on 2017 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer electrolyte membrane (PEM) fuel cells have been viewed as promising power source candidates for transport, stationary, and portable applications due to their high efficiency and low emissions. The platinum is the most commonly used catalyst material for the oxygen reduction reaction (ORR) at the cathode of PEM fuel cells; however, the limited abundance and high cost of platinum hinder the large-scale commercialization of fuel cells. Two approaches being widely accepted to overcome this limitation are 1) to improve Pt utilization to boost the activity while reducing the loading, or 2) to develop non-precious metal catalysts (NPMCs) with sufficient activity and stability to be used in the PEM fuel cells. Despite the ample amount of research and improvements, the activity and stability of these NPMCs must be further improved to be practical in PEMFC applications. The activity can be further enhanced by several different approaches including but not limited to: 1) use of different dopants (nitrogen, boron, sulfur, etc.) precursors, 2) use of different non-platinum group metals (Fe, Co, Mn), 3) utilizing high surface area support materials and 4) applying heat treatment in various conditions. The combination of these approaches affect the active site density and distribution, electronic structure of the active site thus affecting its kinetics and turn over frequency, electrical conductivity and stability of the catalyst in various ways. Herein, two chapters are included exploring with the above mentioned combinations to synthesize highly active and stable catalysts, followed by another chapter investigating its fuel cell performance and discussing possible causes of stability loss with a method to verify the issue with flooding of the microporous active sites. In the first study, non-precious metal oxygen reduction reaction (ORR) catalysts were prepared by pyrolyzing a carbon supported complex consisting of iron acetate coordinated with 1,2,4,5-tetracyanobenzene (TCNB) in an iron phtalocyanine-like polymer arrangement. By employing these small precusursor molecules, it is expected that more uniform and complete coverage of the carbon support material can be obtained, and by using the in situ formation and polymerization of FePc, effective iron-center segregation can be achieved. The results suggest that this type of catalyst has great potential used as a non-precious PEM fuel cell catalyst. In the second study, Co-N decorated porous graphene aerogel catalyst was synthesized as an efficient catalyst for ORR. In the preparation process, polyaniline (PANI) is introduced as a pore-forming agent to aid in the self-assemble of graphene species into a porous aerogel networks, and a nitrogen precursor to induce in situ nitrogen doping. Such highly desired structures can not only expose sufficient active sites for the ORR but also guarantee the fast mass transfer in the catalytic process, which provides significant catalytic activity with positive onset and half wave potentials, low hydrogen peroxide yield and remarkable stability in acid medium. In the last chapter, with a highly microporous catalyst made with dual nitrogen precursors (phenanthroline and polyaniline), a systematic study is performed to investigate micropore flooding in-situ before and after stability testing. The results do not support micropore flooding as being a large contributor to instability, at least for the family of NPMCs evaluated in this work. The protocol outlined here can be used by other researchers in the NPMC community to diagnose micropore flooding in their own respective catalysts. Several recommendations for future work were suggested in the last section of this work to further apply the knowledge to design a highly active, durable, and low-cost NPMCs.

Download or read book Nanostructured Materials Supported Oxygen Reduction Catalysts in Polymer Electrolyte Membrane Fuel Cells written by Ja-Yeon Choi and published by . This book was released on 2013 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: Polymer electrolyte membrane (PEM) fuel cells have been viewed as promising power source candidates for transport, stationary, and portable applications due to their high efficiency and low emissions. The platinum is the most commonly used catalyst material for the oxygen reduction reaction (ORR) at the cathode of PEM fuel cells; however, the limited abundance and high cost of platinum hinder the large-scale commercialization of fuel cells. To overcome this limitation, it is necessary to enhance the catalyst utilization in order to improve the catalytic activity while decreasing or eliminating the use of platinum. The material on which the catalyst is supported is important for the high dispersion and narrow distribution of Pt nanoparticles as well as other non-precious metal active sites, and these characteristics are closely related to electrocatalytic activity of the catalysts. The support materials can influence the catalytic activity by interplaying with catalytic metals, and the durability of the catalyst is also greatly dependent on its support. A variety of support materials like carbons, oxides, carbides, and nitrides have been employed as supports materials for fuel cell catalysts, and much effort has been devoted to the synthesis of the novel carbon supports with large surface area and/or pore volume, including nanostructured carbons such as carbon nanotubes (CNTs), carbon nanofibers, and mesoporous carbon. These novel nanostructured carbon materials have achieved promising performance in terms of catalytic activity and durability. However, there is still enormous demand and potential for the catalysts to improve.

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 Oxygen Reduction Reaction written by Kushal Sengupta and published by Elsevier. This book was released on 2022-06-14 with total page 524 pages. Available in PDF, EPUB and Kindle. Book excerpt: Oxygen Reduction Reaction: Fundamentals, Materials and Applications covers the design, synthesis and performance efficacies of the entire spectrum of oxygen reduction catalysts, extrapolating down to their applications in practical, alternative, renewable energy devices. Catalysts covered include heme inspired iron-based, heme inspired non-iron-based, non-heme-based, noble metal-based, non-noble metal-based and metal-free homogeneous and heterogeneous catalysts. The book contains critical analyses and opinions from experts around the world, making it of interest to scientists, engineers, industrialists, entrepreneurs and students. Discusses the fundamental aspects of oxygen reduction reactions Offers a comprehensive analysis of the choice and development of catalyst materials for oxygen reduction reaction Reviews emerging catalyst systems for oxygen reduction reaction Includes analyses of catalytic performance parameters to evaluate their efficacy in oxygen reduction reactions under varied operating conditions Covers the importance of oxygen reduction reaction catalysts and processes in real-life applications

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.

Download or read book Non precious Metal Based Electrocatalysts for Oxygen Reduction in Proton Exchange Membrane Fuel Cells and Electrolyzers written by Urszula Tylus and published by . This book was released on 2014 with total page 111 pages. Available in PDF, EPUB and Kindle. Book excerpt: The oxygen reduction reaction (ORR) is a key process in various electrochemical energy conversion devices such as fuel cells and metal batteries as it enables CO2-free electrical energy generation. One of the major challenges in these devices is the sluggish kinetics of ORR and thus the need for stable and highly active electrocatalysts. The currently utilized catalytic materials are based on precious group metals (PGM), including platinum, rhodium, or silver. Although the PGM-based catalysts are highly active and reasonably stable under harsh acidic fuel cell conditions, the PGM-systems contribute to high cost of the energy conversion device. This is further aggravated by the high sensitivity of the PGM-catalysts to the presence of small amounts of impurities in the real world environment causing performance decay. These challenges pushed researchers to look for a cost-effective and highly active alternate catalyst materials based on non-precious group metals (non-PGM). Currently, the most promising non-PGM systems are comprised of transition metal-nitrogen-carbon (M-N-C) containing catalysts. Despite several decades of effort to obtain the "perfect" M-N-C catalyst, there is still a fair amount of work to be done mainly towards understanding the origin of ORR activity in these complex M-N-C systems. The objective in these studies is to design the optimal active structure that is able to provide high and selective performance sustained even in very corrosive environments. Element-specific in-situ X-ray absorption spectroscopy (XAS) coupled with standard electrochemical methodology (mainly Rotating Ring Disc Eelectrode, RRDE) is a great tool to study surface active catalytic systems. With a careful experimental design, "in-situ" XAS is able to provide very useful mechanistic information regarding structural properties of the active centers and their behavior in simulated electrochemical environments. Chapter 1 contains a brief description of fundamental aspects of the oxygen reduction reaction, and related challenges. This includes: electrolyte-dependent general description of the ORR mechanistic pathways, and currently known relations between electronic/structural properties of known PGM and non-PGM materials and their catalytic activity. The major electroanalytical and spectroscopic techniques are also discussed, aiming to provide introductory information to the reader needed to understand the experimental work discussed in the following chapters. As the main point of interest is ORR kinetics, which comprise the performance and degradation modes in an aqueous environment, Chapter 2 discusses comparative characteristics of mechanistic ORR pathways (in acid and alkaline media) with a group of the M-N-C catalysts synthesized via various routes. The electroanalytical studies shown in Chapter 2 are followed by more detailed mechanistic investigations (in Chapter 3) wherein the ORR kinetics on the M-N-C catalysts is investigated using "in-situ" spectro-electrochemical XAS methodologies of transition metal centers. Different forms of the metals and their mechanistic roles are investigated by ORR kinetic studies and behavioral monitoring after selective removal or blocking each of the moieties. The information obtained by the mechanistic studies are used in Chapter 4 to discuss the effect of chloride anions on the overall M-N-C activity with the aim to predict their potential use as O2-consuming cathodes in industrial environments involving presence of the chloride species, known to be a strong poison for platinum-based catalysts. Finally, Chapter 5 shows performance non-PGM catalysts developed at NEU based on carbon supported polymer and self-supported Metal Organic Framework (MOF) iron comprising M-N-C catalysts as oxygen depolarized cathodes for recycling of chlorine gas from hydrochloric acid, a common bi-product in industrial chemical plants. Chapter 5 discusses structure-property relationship of the M-N-C catalysts, and their iron-based active centers to overall catalytic performance and stability in such corrosive environment as concentrated hydrochloric acid. The Chapter 5 also covers a promising preliminary study of utilization of the M-N-C catalysts as Oxygen De-polarized Cathodes (ODC) in the chlor-alkali process for Cl2-production. Finally, Chapter 6 summarized the work presented here and discusses future perspectives for applications of the non-PGM catalysts.

Download or read book PEM Fuel Cells written by Gurbinder Kaur and published by Elsevier. This book was released on 2021-11-16 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: PEM Fuel Cells: Fundamentals, Advanced Technologies, and Practical Application provides a comprehensive introduction to the principles of PEM fuel cell, their working condition and application, and the latest breakthroughs and challenges for fuel cell technology. Each chapter follows a systematic and consistent structure with clear illustrations and diagrams for easy understanding. The opening chapters address the basics of PEM technology; stacking and membrane electrode assembly for PEM, degradation mechanisms of electrocatalysts, platinum dissolution and redeposition, carbon-support corrosion, bipolar plates and carbon nanotubes for the PEM, and gas diffusion layers. Thermodynamics, operating conditions, and electrochemistry address fuel cell efficiency and the fundamental workings of the PEM. Instruments and techniques for testing and diagnosis are then presented alongside practical tests. Dedicated chapters explain how to use MATLAB and COMSOL to conduct simulation and modeling of catalysts, gas diffusion layers, assembly, and membrane. Degradation and failure modes are discussed in detail, providing strategies and protocols for mitigation. High-temperature PEMs are also examined, as are the fundamentals of EIS. Critically, the environmental impact and life cycle of the production and storage of hydrogen are addressed, as are the risk and durability issues of PEMFC technology. Dedicated chapters are presented on the economics and commercialization of PEMFCs, including discussion of installation costs, initial capital costs, and the regulatory frameworks; apart from this, there is a separate chapter on their application to the automotive industry. Finally, future challenges and applications are considered. PEM Fuel Cells: Fundamentals, Advanced Technologies, and Practical Application provides an in-depth and comprehensive reference on every aspect of PEM fuel cells fundamentals, ideal for researchers, graduates, and students. Presents the fundamentals of PEM fuel cell technology, electrolytes, membranes, modeling, conductivity, recent trends, and future applications Addresses commercialization, public policy, and the environmental impacts of PEMFC in dedicated chapters Presents state-of-the-art PEMFC research alongside the underlying concepts

Download or read book Nanostructured and Advanced Materials for Fuel Cells written by San Ping Jiang and published by CRC Press. This book was released on 2013-12-07 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: Boasting chapters written by leading international experts, Nanostructured and Advanced Materials for Fuel Cells provides an overview of the progress that has been made so far in the material and catalyst development for fuel cells. The book covers the most recent developments detailing all aspects of synthesis, characterization, and performance.It

Download or read book Heterogeneous Catalysts written by Wey Yang Teoh and published by John Wiley & Sons. This book was released on 2021-02-23 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents state-of-the-art knowledge of heterogeneous catalysts including new applications in energy and environmental fields This book focuses on emerging techniques in heterogeneous catalysis, from new methodology for catalysts design and synthesis, surface studies and operando spectroscopies, ab initio techniques, to critical catalytic systems as relevant to energy and the environment. It provides the vision of addressing the foreseeable knowledge gap unfilled by classical knowledge in the field. Heterogeneous Catalysts: Advanced Design, Characterization and Applications begins with an overview on the evolution in catalysts synthesis and introduces readers to facets engineering on catalysts; electrochemical synthesis of nanostructured catalytic thin films; and bandgap engineering of semiconductor photocatalysts. Next, it examines how we are gaining a more precise understanding of catalytic events and materials under working conditions. It covers bridging pressure gap in surface catalytic studies; tomography in catalysts design; and resolving catalyst performance at nanoscale via fluorescence microscopy. Quantum approaches to predicting molecular reactions on catalytic surfaces follows that, along with chapters on Density Functional Theory in heterogeneous catalysis; first principles simulation of electrified interfaces in electrochemistry; and high-throughput computational design of novel catalytic materials. The book also discusses embracing the energy and environmental challenges of the 21st century through heterogeneous catalysis and much more. Presents recent developments in heterogeneous catalysis with emphasis on new fundamentals and emerging techniques Offers a comprehensive look at the important aspects of heterogeneous catalysis Provides an applications-oriented, bottoms-up approach to a high-interest subject that plays a vital role in industry and is widely applied in areas related to energy and environment Heterogeneous Catalysts: Advanced Design, Characterization and Applications is an important book for catalytic chemists, materials scientists, surface chemists, physical chemists, inorganic chemists, chemical engineers, and other professionals working in the chemical industry.

Download or read book Non precious Metal Electrocatalysts for the Oxygen Reduction Reaction in Proton Exchange Membrane PEM Fuel Cells written by Deepika Singh and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The growth process of nitrogen-doped carbon nano-structures (CNx) was studied using in-situ and ex-situ characterization techniques. It was found that the Co phase was seen to go through different transformations during the pyrolysis process, depending on the growth substrate used. CNx fibers that formed were acid-washed, and the structure of CNx obtained as well as the nitrogen content was significantly different on the two substrates, which led to activity differences seen in RRDE.