Investigation of Faceted Fuel Cell Catalyst Nanoparticles by Transmission Electron Microscopy PDF Download
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Author: Martin Gocyla
Publisher:
ISBN:
Category : Fuel
Languages : en
Pages :
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Author: Martin Gocyla
Publisher:
ISBN:
Category : Fuel
Languages : en
Pages :
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Author: Elliot Padgett
Publisher:
ISBN:
Category :
Languages : en
Pages : 225
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Hydrogen fuel cells in fuel cell electric vehicles (FCEVs) are a promising technology to reduce, and eventually eliminate, carbon dioxide emissions from transportation. The Pt nanoparticles used to catalyze the fuel cell's electrochemical reactions are an important limiting factor because at present levels, the cost of the Pt catalyst will prevent widespread adoption of FCEVs. Catalysts must be developed to reduce the amount of Pt while meeting vehicle power demands even after many years of use. Strategically improving catalysts requires detailed and statistically robust characterization of their microscopic structure to understand the connections between catalyst synthesis, structure, performance, and durability. This dissertation presents the development and application of (scanning) transmission electron microscopy ((S)TEM) techniques to guide advancement of catalysts through nanostructural characterization. We develop a robust strain mapping technique for complex catalyst specimens. We deploy a new exit wave power cepstrum (EWPC) transform to nanobeam electron diffraction (NBED) patterns to enable precise, high-throughput, dose-efficient strain measurement. This approach is suitable for statistically representative measurements of many particles without special requirements such as zone-axis orientation. We apply this strain mapping technique to core-shell Pt-Co nanoparticles in combination with a continuum elastic theory model and demonstrate two mechanisms contributing to the relaxation of strain at the catalyst surface: lattice dislocations and Poisson expansion due to the spherical geometry. Comparison with electrochemical measurements suggests that the geometrical Poisson relaxation accounts for the activity of catalysts with thin shells, but catalysts with thick shells experience additional activity loss from dislocation-driven relaxation. We then turn to the larger-scale catalyst structure, investigating the impact of porous carbon support morphology, local reactant transport, and catalyst durability. Using statistical analysis of STEM images, we compare Pt and Pt-Co catalysts on porous and solid carbon supports. Comparison of 3D tomographic images and electrochemical accessibility measurements indicated that carbon pores prevent ionomer adsorption for particles embedded within them, improving the catalyst activity, while allowing proton access through condensed water. By comparing images and composition maps before and after electrochemical stability tests, we find that porous carbon supports suppress Pt particle coalescence, accounting for improved overall durability.
Author: Dai-Ming Tang
Publisher: Springer Science & Business Media
ISBN: 3642372597
Category : Technology & Engineering
Languages : en
Pages : 131
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Using an in situ transmission electron microscopy (TEM) approach to investigate the growth mechanism of carbon nanotubes (CNTs) as well as the fabrication and properties of CNT-clamped metal atomic chains (MACs) is the focus of the research summarized in this thesis. The application of an in situ TEM approach in the above-mentioned research provides not only real-time observation but also monitored machining and structural evolvement at the atomic level. In this thesis, the author introduces a CNT tubular nano furnace that can be operated under TEM for investigation of the CNT nucleation mechanism. By studying the nucleation process of CNTs in the presence of various catalysts, including iron-based metallic catalysts and silicon oxide-based non-metallic catalysts, the physical states of the catalysts as well as the nucleation and growth process of CNTs are revealed. Based on the understanding of the nucleation mechanism, the author proposes a hetero-epitaxial growth strategy of CNTs from boron nitride, which provides a new route for the controllable growth of CNTs. In addition, the author presents an electron beam-assisted nanomachining technique and the fabrication of a CNT-clamped MAC prototype device based on this technique. The formation process of CNT-clamped Fe atomic chains (ACs) can be monitored with atomic resolution. The demonstrated quantized conductance and uninfluenced half-metallic properties of Fe ACs indicate that CNTs can be promising nanoscale electrodes or interconnectors for the linking and assembly of nano and subnano structures.
Author: Philipp A. Heizmann
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Kenneth I. Ozoemena
Publisher: Springer
ISBN: 3319299301
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: Shangfeng Du
Publisher: Academic Press
ISBN: 0128111135
Category : Technology & Engineering
Languages : en
Pages : 97
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Book Description
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: Frances M. Ross
Publisher: Cambridge University Press
ISBN: 1107116570
Category : Science
Languages : en
Pages : 529
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2.6.2 Electrodes for Electrochemistry
Author: Jaroslava Lavková
Publisher:
ISBN:
Category :
Languages : en
Pages : 298
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Book Description
Present doctoral thesis is focused on investigation of novel metal-oxide anode catalyst for fuel cell application by electron microscopy and associated spectroscopies. Catalysts based on Pt-doped cerium oxide in form of thin layers prepared by simultaneous magnetron sputtering deposition on intermediate carbonaceous films grown on silicon substrate have been studied. The influence of the catalyst support composition (a-C and CNx films), deposition time of CeOx layer and other deposition parameters, as deposition rate, composition of working atmosphere and Pt concentration on the morphology of Pt-CeOx layers has been investigated mainly by Transmission Electron Microscopy (TEM). The obtained results have shown that by combination of suitable preparation conditions we are able to tune the final morphology and composition of the catalysts. The composition of carbonaceous films and Pt-CeOx layers was examined by complementary spectroscopy techniques - Energy Dispersive X-ray Spectroscopy (EDX), Electron Energy Loss Spectroscopy (EELS) and X-ray Photoelectron Spectroscopy (XPS). Such prepared porous structures of Pt-CeOx are promising as anode catalytic material for real fuel cell application.
Author: Inamuddin
Publisher: Materials Research Forum LLC
ISBN: 1644900181
Category : Technology & Engineering
Languages : en
Pages : 399
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Book Description
Alcohol fuel cells are very attractive as power sources for mobile and portable applications. As they convert the chemical energy of fuels into electricity, much recent research is directed at developing suitable and efficient catalysts for the process. The present book focuses on pertinent types of nanomaterial-based catalysts, membranes and supports.
Author: Ariel Jackson
Publisher:
ISBN:
Category :
Languages : en
Pages :
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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.
