Author: Ntombizodwa Ruth MathePublisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 408
Book Description
Synthesis and Characterization of Bimetallic Platinum Nanoparticles for Use in Catalysis
Author: Ntombizodwa Ruth MathePublisher:
ISBN:
Category : Catalysis
Languages : en
Pages : 408
Book Description
Synthesis and Characterization of Bimetallic Platinum-gold Catalysts
Author: Corina MihutGreen Synthesis, Characterization and Applications of Nanoparticles
Author: Ashutosh Kumar ShuklaPublisher: Elsevier
ISBN: 0081025807
Category : Technology & Engineering
Languages : en
Pages : 548
Book Description
Green Synthesis, Characterization and Applications of Nanoparticles shows how eco-friendly nanoparticles are engineered and used. In particular, metal nanoparticles, metal oxide nanoparticles and other categories of nanoparticles are discussed. The book outlines a range of methodologies and explores the appropriate use of each. Characterization methods include spectroscopic, microscopic and diffraction methods, but magnetic resonance methods are also included as they can be used to understand the mechanism of nanoparticle synthesis using organisms. Applications covered include targeted drug delivery, water purification and hydrogen generation. This is an important research resource for those wishing to learn more about how eco-efficient nanoparticles can best be used. Theoretical details and mathematical derivations are kept to a necessary minimum to suit the need of interdisciplinary audiences and those who may be relatively new to the field. Explores recent trends in growth, characterization, properties and applications of nanoparticles Gives readers an understanding on how they are applied through the use of case studies and examples Assesses the advantages and disadvantages of a variety of synthesis and characterization techniques for green nanoparticles in different situations
Synthesis and Characterization of a Bimetallic Platinum(II) Complex
Author: James William GeminPublisher:
ISBN:
Category : Metal-metal bonds
Languages : en
Pages : 72
Book Description
Controlled Synthesis of Pt-Ni Bimetallic Catalysts and Study of Their Catalytic Properties
Author: Yuen WuPublisher: Springer
ISBN: 3662498472
Category : Science
Languages : en
Pages : 119
Book Description
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.
Bimetallic Nanoparticles
Author: Alexandra Marcela LandryPublisher:
ISBN:
Category :
Languages : en
Pages : 92
Book Description
Bimetallic nanoparticles can lead to catalysts with improved turnover rates and selectivities, but many synthetic protocols, such as impregnation or precipitation, typically form particles of non-uniform size and composition. Colloidal methods may be able to improve their uniformity, but often require reagents that poison catalytic surfaces (ex. S, B, P). Such compositional non-uniformity and ubiquitous impurities have prevented rigorous conclusions about the consequences of alloying on reactivity and selectivity. Herein, we describe a sequential galvanic displacement-reduction (GDR) colloidal synthesis method using precursors containing only C, H, O, and N, that leads to bimetallic AuPt and PtPd nanoparticles narrowly distributed in size and composition. Au3+ or Pt4+ precursors were added to monometallic Pt or Pd clusters, respectively, whose surface atoms are thermodynamically driven to reduce and deposit the solvated cations onto cluster surfaces due to the lower reduction potentials (E0) of the seed metal relative to the precursor cations (E0Au> E0Pt> E0Pd); oxidized Pt and Pd surface atoms subsequently return to cluster surfaces upon reduction by the solvent, a reductant (ethanol or ethylene glycol, respectively). Such methods have been previously used to synthesize AuPd clusters from Pd seed clusters. TEM micrographs confirm that initial seed cluster sizes increase monotonically with increasing Au3+ or Pt4+ content, with final bimetallic cluster dispersity values near unity indicating a narrow size distribution. UV visible spectroscopy of AuPt cluster suspensions show no plasmon resonance features characteristic of Au nano-sized surfaces, indicating the presence of Pt atoms at bimetallic surfaces, as expected for GDR processes. Elemental analysis by EDS confirmed the formation of strictly bimetallic particles with the mean composition of the synthesis mixture. The GDR model requires that bimetallic growth be proportional to the initial seed surface area, with the number of precursor atoms deposited per surface metal atom of the seed constant and independent of seed metal size. Elemental analysis using EDS supports this hypothesis for thermodynamically favorable alloys such as PtPd and AuPd, but not for AuPt, an unfavorable alloy. These differences appear to reflect the segregation of metals within AuPt clusters during synthesis, placing the metal with the lower surface energy, Au, at cluster surfaces, and decreasing the availability of Pt0 surface atoms for GDR. Consequently, autocatalytic Au3+ reduction on Au0 sites becomes a competitive Au3+ reduction pathway during the synthesis of AuPt clusters. Polymers such as polyvinylpyrrolidone (PVP)--which bind to metal surfaces during synthesis via charge-transfer interactions--were required in colloidal suspensions to prevent particle agglomeration in solution, but must be removed prior to catalysis. We show that after depositing clusters on SiO2, PVP can be removed from particle surfaces by post-synthetic treatments at mild temperatures (d"423 K) in reductants such as H2 and/or EtOH without significant particle agglomerations. Reductants compete with the polymer at the metal surface, thus breaking the polymer-metal bond. The absence of surface residues was confirmed by the similar cluster sizes derived from O2 chemisorption and TEM measurements. Larger cluster sizes and surfaces that chemisorb oxygen more weakly--such as Pt relative to Pd--were found to facilitate the removal of PVP from metal particles due to weaker metal-polymer bonds. The model catalytic materials prepared in this study are of both fundamental and practical interest to probe the effects of alloying. Using AuPd and AuPt, we investigate the consequences of alloying with Au on the reactivity of catalyst surfaces saturated with either chemisorbed CO* (CO oxidation) or O* (H2 oxidation) that bind strongly to Pt and Pd surfaces and inhibit rates. Singleton Pt-CO* bond energies, reflected in vibrational CO* stretches, were decoupled from dipole-dipole coupling effects using isotopic dilution methods, and were shown to decrease with increasing catalyst Au content. Despite lower CO* binding energies, CO oxidation turnover rates (normalized per metal surface atom) on AuPt catalysts decreased with increasing Au content. These results show that CO oxidation rates depend weakly on CO* binding energy--consistent with the reported structed insensivity of this reaction--and that Au acts primarily as an inert diluent of the active Pt ensembles required for catalysis. In contrast, H2 oxidation turnover rates (normalized per metal surface atom) on AuPt and AuPd catalysts increase with increasing Au content (up to 11 % at. Au content on AuPt and up to 67 % at. Au content on AuPd), indicating that the reactivity of O* saturated surfaces is more sensitive to changes in adsorbate binding energy than surfaces saturated in CO*, consisted with the reported structure sensitivity of reactions on O* saturated surfaces. Reconstruction of CO* adlayers is facile due to highly mobile CO* molecules, thus allowing CO* adlayers to access configurations that help mitigate strong CO* binding and introduce vacancies. O* adlayers, meanwhile, are more strongly bound to Pt and Pd metal surfaces and less mobile. H2 oxidation rates thus depend more strongly on adsorbate binding energy than CO oxidation rates.
Metal Nanoclusters in Catalysis and Materials Science: The Issue of Size Control
Author: Benedetto CorainPublisher: Elsevier
ISBN: 0080555004
Category : Technology & Engineering
Languages : en
Pages : 471
Book Description
Metal Nanoclusters in Catalysis and Materials Science: The Issue of Size Control deals with the synthesis of metal nanoclusters along all known methodologies. Physical and chemical properties of metal nanoclusters relevant to their applications in chemical processing and materials science are covered thoroughly. Special attention is given to the role of metal nanoclusters size and shape in catalytic processes and catalytic applications relevant to industrial chemical processing.An excellent text for expanding the knowledge on the chemistry and physics of metal nanoclusters. Divided in two parts; Part I deals with general aspects of the matter and Part II has to be considered a useful handbook dealing with the production of metal nanoclusters, especially from their size-control point of view. * Divided into two parts for ease of reference: general and operational * Separation of synthetic aspects, physical properties and applications* Specific attention is given to the task of metal nanoclusters size-control
Author: Hui Wang
Author: Paul Chang
Author: Hui Wang