Synthesis of Shape-specific Platinum Nanoparticles, Their Performance as Fuel Cell Catalysts, and Other Novel Nanocomposite Materials for Alternative Energy Technologies PDF Download

Author: Jason A. Michel
Publisher:
ISBN:
Category : Fuel cells
Languages : en
Pages : 392

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Author: Shangfeng Du
Publisher: Academic Press
ISBN: 0128111135
Category : Technology & Engineering
Languages : en
Pages : 97

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One-dimensional Nanostructures for PEM Fuel Cell Applications provides a review of the progress made in 1D catalysts for applications in polymer electrolyte fuel cells. It highlights the improved understanding of catalytic mechanisms on 1D nanostructures and the new approaches developed for practical applications, also including a critical perspective on current research limits. The book serves as a reference for the design and development of a new generation of catalysts to assist in the realization of successful commercial use that have the potential to decarbonize the domestic heat and transport sectors. In addition, a further commercialization of this technology requires advanced catalysts to address major obstacles faced by the commonly used Pt/C nanoparticles. The unique structure of one-dimensional nanostructures give them advantages to overcome some drawbacks of Pt/C nanoparticles as a new type of excellent catalysts for fuel cell reactions. In recent years, great efforts have been devoted in this area, and much progress has been achieved. Provides a review of 1D catalysts for applications in polymer electrolyte fuel cells Presents an ideal reference for the design and development of a new generation of catalysts to assist in the realization of successful commercial use Highlights the progress made in recent years in this emerging field

Author: Shuhu Sun
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Proton exchange membrane fuel cells (PEMFCs) are promising energy converting technologies to generate electricity by mainly using hydrogen as a fuel, producing water as the only exhaust. However, short life-time and high cost of Pt catalyst are the main obstacles for the commercialization of PEMFCs. In the conventional carbon black upported platinum nanoparticle (NP) commercial catalyst, carbon supports are prone to oxidation and corrosion over time that results in Pt NPs migration, coalescence, even detaching from the catalyst support. In addition, Ostwald ripening of the Pt NPs could also occur due to their high surface energy and zero dimensional structural features. All these contribute to the degradation of fuel cell performance. This research aims at fabricating various advanced nanomaterials, including (1) Pt-based highly efficient nanocatalysts and (2) alternative nanostructured durable catalyst supports, to address the above-mentioned challenges in PEMFCs. It is well known that the catalytic activity and durability of Pt catalysts are highly dependent on their size and shape. In contrast to commercially-used Pt spherical nanoparticles, one-dimensional (1D) structures of Pt, such as nanowires (NWs), exhibit additional advantages associated with their anisotropy and unique structure. We first reported a new approach to address both activity and durability challenges of PEM fuel cells by using 1D Pt nanowires (PtNWs) as electrocatalyst. Pt NWs were synthesized via a very simple environmentally-friendly aqueous solution route at room temperature, without the need of heating, surfactants or complicated experimental apparatus. This novel PtNW nanostructure showed much improved activity and durability than the state-of-the-art commercial Pt/C catalyst which is made of Pt nanoparticles. Further, Pt NWs were grown on Sn@CNT nanocable support to form a novel 3D fuel-cell electrode (PtNW/Sn@CNT). This approach allows us to combine the advantages of both PtNW catalyst and Sn@CNT 3D nanocable support for fuel cell applications. The PtNW/Sn@CNT 3D electrodes showed greatly enhanced electrocatalytic activities for ORR, MOR and improved CO tolerance than commercial Pt/C nanoparticle catalyst. To save more platinum, ultrathin Pt NWs with even smaller diameters of 2.5 nm (vs. 4 nm reported in our previous work) have been successfully synthesized when using N-doped CNTs as support. Direct evidence for the formation of ultrathin Pt NWs was provided by systematically investigating their growth process under TEM. Nitrogen doping in CNTs played a key role in the formation of ultrathin Pt nanowires. In terms of low durability of PEM fuel cell catalysts, the corrosion of current commonly-used carbon black support materials have been identified to be the major contributor to the catalyst failure. One of the major challenges lies in the development of inexpensive, efficient, and highly durable alternative catalyst supports that possess high corrosion resistance, high conductivity and high surface area. In this work, a series of promising alternative nanostructured catalyst supports, including 0D Nb-doped CNTs as support. Direct evidence for the formation of ultrathin Pt NWs was provided by systematically investigating their growth process under TEM. Nitrogen doping in CNTs played a key role in the formation of ultrathin Pt nanowires. In terms of low durability of PEM fuel cell catalysts, the corrosion of current commonly-used carbon black support materials have been identified to be the major contributor to the catalyst failure. One of the major challenges lies in the development of inexpensive, efficient, and highly durable alternative catalyst supports that possess high corrosion resistance, high conductivity and high surface area. In this work, a series of promising alternative nanostructured catalyst supports, including 0D Nb-doped TiO2 hollow nanospheres, 1D TiSix-NCNT nanostructures, and 2D graphene nanosheets, have been synthesized by various methods and used as catalyst supports. Pt nanoparticles were then deposited on these novel supports, showing enhanced catalytic activities and durabilities. Most interestingly, a new technique, atomic layer deposition (ALD), was used to uniformly deposit Pt nanoparticles, subnanometer clusters and single atoms on graphene nanosheets. Downsizing Pt nanoparticles to clusters or even single atoms could significantly increase their catalytic activity and is therefore highly desirable to maximize the efficiency. In summary, the discoveries in this thesis contribute to applying various novel nanostructured materials to design highly active and stable electrocatalyst and durable catalyst support to develop high performance and low cost PEM fuel cells.

Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 906

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

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

Author: Yuen Wu
Publisher: Springer
ISBN: 3662498472
Category : Science
Languages : en
Pages : 119

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This thesis focuses on the controlled synthesis of Pt–Ni bimetallic nanoparticles and the study of their catalytic properties. It discusses in detail the nucleation mechanism and the growth process of bimetallic systems, which is vital for a deeper understanding of the design of bimetallic catalysts. The author presents four pioneering studies: (1) syntheses of water-soluble octahedral, truncated octahedral, and cubic Pt–Ni nanocrystals and the study of their structure-activity relationship in model hydrogenation reactions; (2) a strategy for designing a concave Pt–Ni alloy using controllable chemical etching; (3) defect-dominated shape recovery of nanocrystals, which is a new synthesis strategy for trimetallic catalysts; (4) a sophisticated construction of Au islands on Pt−Ni, which is an ideal trimetallic nanoframe catalyst. This thesis inspires researchers working in materials, catalysis as well as other interdisciplinary areas.

Author: Md Ariful Hoque
Publisher:
ISBN:
Category :
Languages : en
Pages : 128

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The pressing demand for high performance, operationally stable and inexpensive electrocatalyst materials for proton exchange membrane fuel cells (PEMFCs) has spurred significant research and development interest in this field. Until now, fuel cells based on commercially available Pt/C electrocatalysts have not met some of the technical challenges to the widespread commercial adoption of PEMFCs. The main issues associated with the commercial validity of PEMFCs are the high cost and inadequate long term operational stability of Pt/C catalysts typically used to facilitate the inherently sluggish oxygen reduction reaction (ORR). Therefore, the replacement of Pt/C with novel and more effective catalyst materials is critical. These expensive precious metal catalysts make up a large portion of the overall PEMFC stack cost and suffer degradation under harsh potentiodynamic conditions. Therefore, careful electrocatalyst design strategies must be developed to reduce the cost of ORR catalysts with sufficient activity and stability to meet the technical targets set for the use of PEMFCs. In this work, two approaches are applied to develop new electrocatalyst materials for PEMFCs. The first is to design unique sulfur-doped graphene (SG) and sulfur-doped CNT (S-CNT) supports with the objective of replacing the traditional carbon black to enhance stability toward carbon corrosion. The second is to deposit Pt nanoparticles and nanowires onto SG and S-CNT with the objective of exceeding the activity and stability possible with conventional catalysts. These two catalyst technologies are developed with the ultimate objective of integrating the Pt electrodes into membrane electrode assembly (MEA) to provide excellent PEMFC performance. The first study focuses on the use of SG prepared by a thermal shock/quench anneal process as a unique Pt nanoparticle support (Pt/SG). These materials are subjected to a variety of physicochemical characterizations and electrochemical investigation for the ORR. Based on half-cell electrochemical testing in acidic electrolyte, Pt/SG demonstrated increased ORR activity and unprecedented stability over the state-of-the-art commercial Pt/C, maintaining 87% of its electrochemically active surface area following accelerated durability testing. Density functional theory (DFT) calculations highlighted that the interactions between Pt and graphene are enhanced significantly by sulfur doping, leading to a tethering effect that can explain the outstanding electrochemical stability. Furthermore, sulfur dopants resulted in a downshift of the Pt d-band center, explaining the excellent ORR activity and rendering SG as a new and highly promising class of catalyst supports for electrochemical energy technology and PEMFCs. The beneficial impacts of SG support can be utilized by growing more stable nanostructures such as Pt nanowires on SG to further improve the activity and stability of Pt catalysts. Toward this end, we carried out the direct growth of platinum nanowires on SG (PtNW/SG) by a simple, surfactant free solvothermal technique. The growth mechanism, including Pt nanoparticle nucleation on SG, followed by nanoparticle attachment with orientation along the 111 direction is also highlighted. PtNW/SG demonstrated increased Pt mass activity and a specific activity that is 188% higher than state-of-the-art commercial Pt/C catalysts. Most notably, under a harsh potentiodynamic condition (potential cycles: 3000, potential range: 0.05 to 1.5 V vs RHE), PtNW/SG retained 58% of its electrochemically active surface area and 67% of its ORR activity in comparison to Pt/C that retained less than 1% of its surface area and activity and so failed. Given the evidence that SG is a promising support for Pt catalysts, the next logical step is to investigate the influence of sulfur on catalytic materials. Accordingly, we study the effects of sulfur on the electrochemical activity and stability of various SG supported platinum nanowires (PtNW/SGs). To investigate the influence of sulfur, a series of SG materials with varying sulfur contents ranging from 0.35 to 3.95 at% are investigated as Pt nanowire catalyst supports. Based on the physico-chemical characterizations, electrochemical measurements and DFT calculations, the amount of sulfur is shown to significantly affect the electrokinetics of the Pt nanowires. The best ORR kinetics are observed for the Pt nanowires supported on graphene with 1.40 at% sulfur. At higher sulfur contents, further enhancements are not observed, and in fact, leads to a loss of activity. At lower sulfur contents, the beneficial role of sulfur does not have a marked impact on performance so that the characteristics and performance more closely resemble that obtained with undoped graphene supports. Obviously, the beneficial effect of sulfur dopant species can be utilized by doping sulfur into other types of carbon supports such as CNT (S-CNT). Finally, we report on the synthesis, characterization and electrochemical evaluation of S-CNT-supported Pt nanowires (PtNW/S-CNT). PtNW/S-CNT synthesized by a modified solvothermal method demonstrated an increased mass activity and a specific activity 570% higher than state-of-the-art Pt/C. The stability of PtNW/S-CNT is also shown to be very impressive through accelerated degradation testing. Only insignificant changes to the electrochemically active surface area (ECSA, 93% retention) and mass activity (81% retention) of PtNW/S-CNT are observed over the course of cycling, in contrast to sizable losses observed with commercial Pt/C (

Author: Kenneth I. Ozoemena
Publisher: Springer
ISBN: 9783030104122
Category : Science
Languages : en
Pages : 583

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Global experts provide an authoritative source of information on the use of electrochemical fuel cells, and in particular discuss the use of nanomaterials to enhance the performance of existing energy systems. The book covers the state of the art in the design, preparation, and engineering of nanoscale functional materials as effective catalysts for fuel cell chemistry, highlights recent progress in electrocatalysis at both fuel cell anode and cathode, and details perspectives and challenges in future research.

Author: Jianbo Wu
Publisher:
ISBN:
Category :
Languages : en
Pages : 217

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Book Description
"With rapid depletion of fossil fuel and the increasing concern over CO2 release, there is an urgent need to develop a new technology using alternative energy sources. Polymer electrolyte membrane fuel cell (PEMFC) is considered one of the promising technologies due to their high energy efficiency, and environmental friendliness. Platinum has been widely used as electrocatalyst in PEMFCs because of its ability to absorb and dissociate important chemical species, such as hydrogen and oxygen. The high cost of platinum used in the electrocatalysts however hinders the real world applications of PEMFCs. It is critical that consumption of platinum be reduced without sacrificing catalytic performance. Highly active and durable electrocatalysts with low Pt content need to be developed in order to advance the fuel cell technology. Studies have demonstrated that both d-band electron and surface geometric structure can greatly affect the activity of catalysts and be optimized by tailoring their composition and surface. In this thesis I present the synthesis, characterization and electrochemical property of facet-controlled platinum bimetallic alloy nanoparticles. A series of Pt-M (M= Co, Cu, Fe, Ni and Pd) bimetallic alloys with various shapes bounded with {111} or {100} facets have been prepared and their electrocatalytic properties have been tested. The surface-defined Pt3Ni nanocrystals have exhibited enhanced activity in oxygen reduction reaction (ORR), which is proportional to the surface ratio of {111} over {100} facets, when the shape of Pt3Ni nanocrystals changes gradually from cube to truncated octahedron, and to octahedron. Beyond the shape-controlled synthetic approach assisted by commonly used capping agents and reducing agents to produce bimetallic alloy nanocrystals with different compositions. CO, a gaseous reducing agent, was introduced to control the morphology of platinum alloys. Electrochemical stripping and Fourier transform infrared spectroscopy (FTIR) were used to show the strong facet-sensitive adsorption and oxidation play the key roles for the shape-controlled synthesis. This facet-preferential adsorption and oxidation property was also applied to address the issue on CO poisoning in methanol oxidation reaction (MOR). The size-dependent ORR catalytic properties of {111} surface-dominated octahedral Pt3Ni nanocrystals were examined in order to narrow the gap in ORR activity shown between the nanocrystal catalysts and extended single crystal surface of Pt3Ni alloys. The area-specific ORR activities of Pt3Ni catalysts at 0.9 V were 0.85 mA/cm2 Pt for the nanocubes, and 1.26 mA/cm2 Pt for the nanooctahedra. The ORR mass activity of the octahedral Pt3Ni catalyst reached 0.44 A/mg Pt. Pt-M (M = Au, Ni, Pd) alloy icosahedral nanocrystals was obtained based on CO assisted reduction methods. The area specific activity of icosahedral Pt3Ni catalysts (1.82 mA/cm2Pt) was about 50% higher than that of the octahedral (1.26 mA/cm2Pt), even though both shapes are bounded by {111} facets. Density functional theory (DFT) calculation and molecular dynamic simulation results showed that this improvement may come from strain-induced electronic effects. A quantitative surface segregation model on durability of bimetallic alloy ORR catalysts was established by studying the anisotropic diffusion coefficient, diffusion length and atomic size of non-platinum metals"--Pages v-vi.

Author:
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Category :
Languages : en
Pages :

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While gold and platinum have long been recognized for their beauty and value, researchers at the Savannah River National Laboratory (SRNL) are working on the nano-level to use these elements for creative solutions to our nation's energy and security needs. Multiinterdisciplinary teams consisting of chemists, materials scientists, physicists, computational scientists, and engineers are exploring unchartered territories with shape-selective nanocatalysts for the development of novel, cost effective and environmentally friendly energy solutions to meet global energy needs. This nanotechnology is vital, particularly as it relates to fuel cells. SRNL researchers have taken process, chemical, and materials discoveries and translated them for technological solution and deployment. The group has developed state-of-the art shape-selective core-shell-alloy-type gold-platinum nanostructures with outstanding catalytic capabilities that address many of the shortcomings of the Direct Methanol Fuel Cell (DMFC). The newly developed nanostructures not only busted the performance of the platinum catalyst, but also reduced the material cost and overall weight of the fuel cell.