Theses and Dissertations from UMD

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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

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Subject: search.filters.subject.Chemistry, Inorganic

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    Bottom-Up Multiferroic Nanostructures
    (2009) Ren, Shenqiang; Wuttig, Manfred; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Multiferroic and especially magnetoelectric (ME) nanocomposites have received extensive attention due to their potential applications in spintronics, information storage and logic devices. The extrinsic ME coupling in composites is strain mediated via the interface between the piezoelectric and magnetostrictive components. However, the design and synthesis of controlled nanostructures with engineering enhanced coupling remain a significant challenge. The purpose of this thesis is to create nanostructures with very large interface densities and unique connectivities of the two phases in a controlled manner. Using inorganic solid state phase transformations and organic block copolymer self assembly methodologies, we present novel self assembly "bottom-up" techniques as a general protocol for the nanofabrication of multifunctional devices. First, Lead-Zirconium-Titanate/Nickel-Ferrite (PZT/NFO) vertical multilamellar nanostructures have been produced by crystallizing and decomposing a gel in a magnetic field below the Curie temperature of NFO. The ensuing microstructure is nanoscopically periodic and anisotropic. The wavelength of the PZT/NFO alternation, 25 nm, agrees within a factor of two with the theoretically estimated value. The macroscopic ferromagnetic and magnetoelectric responses correspond qualitatively and semi-quantitatively to the features of the nanostructure. The maximum of the field dependent magnetoelectric susceptibility equals 1.8 V/cm Oe. Second, a magnetoelectric composite with controlled nanostructures is synthesized using co-assembly of two inorganic precursors with a block copolymer. This solution processed material consists of hexagonally arranged ferromagnetic cobalt ferrite (CFO) nano-cylinders within a matrix of ferroelectric Lead-Zirconium-Titanate (PZT). The initial magnetic permeability of the self-assembled CFO/PZT nanocomposite changes by a factor of 5 through the application of 2.5 V. This work may have significant impact on the development of novel memory or logic devices through self assembly techniques. It also demonstrates a universal two-phase hard template application. Last, solid-state self assembly had been used recently to form pseudoperiodic chessboard-like nanoscale morphologies in a series of chemically homogeneous complex oxide systems. We improved on this approach by synthesizing a spontaneously phase separated nanolamellar BaTiO3-CoFe2O4 bi-crystal. The superlattice is magnetoelectric with a frequency dependent coupling. The BaTiO3 component is a ferroelectric relaxor with a Vogel-Fulcher temperature of 311 K. Since the material can be produced by standard ceramic processing methods, the discovery represents great potential for magnetoelectric devices.
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    TEMPLATE SYNTHESIZED NANOTUBES, NANOWIRES AND HETEROGENEOUS COAXIAL NANOWIRES FOR ELECTROCHEMICAL ENERGY STORAGE
    (2009) Liu, Ran; Lee, Sang Bok; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Template synthesized nanomaterials have been successfully applied in electrochemical energy storage systems such as supercapacitors and lithium ion batteries. The first part of present study will list examples of applying various nanomaterials such as nanowires, nanotubes and heterostructured nanowires in different electrochemical energy storage systems for enhancing their charge/discharge rates, energy densities and power densities, etc. The following of the thesis will describe the template synthesis of nanomaterials in details. The experimental part of this thesis will concentrate on the fabrication of alumina template and the detailed experimental setups for aluminum anodization and template synthesis of nanomaterials. The rest of the thesis analyzes four cases of using template synthesized nanomaterials in electrochemical energy storage, which include my major work during my PhD studies. The first one is utilizing poly(3,4- ethylenedioxythiophene) (PEDOT) nanotubes as electrode materials for highpowered supercapacitor. The thin-walled nanotubes allow fast charge/discharge of the PEDOT to achieve high power. The second one is related to synthesis and characterization of RuO2/PEDOT composite nanotubes for supercapacitors. Loading appropriate amount of RuO2 can effectively enhance the specific capacitance of PEDOT nanotube. The third case illustrates the synthesis of MnO2/PEDOT coaxial nanowires by one step coelectrodeposition for electrochemical energy storage. The combined properties of MnO2 and PEDOT enable the coaxial nanowires to have very high specific capacitances at high current densities. Their formation mechanism will be explored and their nanostructures are tuned for optimized electrochemical properties. The final case reports the MnO2-Nanoparticles enriched PEDOT nanowires for enhanced electrochemical energy storage capacity. Large amount of the MnO2 nanoparticles can be loaded into PEDOT nanowires after they are soaked in KMnO4 solution. Thus loaded MnO2 nanoparticles effective enhance the energy densities of PEDOT nanowires without causing too much volume expansion to them.
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    Synthesis, Characterization and Catalytic Properties of Bimetallic Nanoparticles
    (2009) Dylla, Anthony Greg; Walker, Robert A; Eichhorn, Bryan W; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Due to the ever-increasing desire for catalysts that possess high activities and selectivities for industrially relevant reactions, much effort is being spent on the synthesis of mono and bimetallic nanoparticles with tunable characteristics such as size, shape and bimetallic composition. Understanding how these characteristics influence catalytic performance is the key to rationally designing catalysts for a specific reaction. While significant breakthroughs have been made, particularly in the area of monometallic nanoparticles with regard to shape and size, relating the bimetallic structure, i.e., core@shell or alloy to a specific reactivity remains a difficult task. Work presented in this thesis describes the synthesis, characterization and catalytic properties of mono and bimetallic nanoparticles. Our efforts were motivated by the desire to understand the relationships that exist between metallic nanoparticle structure and their function as catalysts. This work also seeks to better understand the dynamic changes a nanoparticle's structure undergoes during typical catalytic operating conditions. Our approach is to use a wide array of analytical tools including optical methods, electron microscopy, XRD and mass spectrometry to provide an interlocking description of nanoparticle structure, function and durability. We show how the polymer coatings and degraded carbonaceous deposits affect propene hydrogenation catalytic activity of Pt nanoparticles. We also present a unique view of the interplay between thermodynamic and kinetic variables that control bimetallic nanoparticle alloy structures by looking at ordered and disordered PdCu alloy nanoparticles as a function of particle size. In another study we show that Ru@Pt and PtRu alloy nanoparticle catalysts have similar surface structures under oxidizing conditions but completely different surface structures under reducing conditions as probed by vibrational spectroscopy. These differences and similarities in surface composition correlate very well to their catalytic activity for CO oxidation under oxidizing and reducing environments, respectively. Finally, we present the synthesis and characterization of Cu@Pt nanoparticles with a particular focus on the core@shell formation mechanism. We also show how dramatic changes in the surface electronic structure of Cu versus Cu@Pt nanoparticles can affect their ability to transform light into heat by using Raman spectroscopy to observe graphite formation on the surface of these nanoparticles.
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    LIGAND-ENABLED PLATINUM--CARBON BOND FUNCTIONALIZATION UTILIZING DIOXYGEN AS THE TERMINAL OXIDANT
    (2009) Khusnutdinova, Julia; Vedernikov, Andrei N.; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The use of organotransition metal complexes for selective functionalization of hydrocarbons is of great importance. Dioxygen is the most practical oxidant for large-scale applications in the petroleum industry. The focus of this work is the development of ligand-modulated platinum-based systems that can utilize O2 or air for selective transformation of organoplatinum(II) derivatives into alcohols, diols, aminoalcohols and epoxides in aqueous media. We found that the hemilabile tripod ligand dipyridylmethanesulfonate (dpms) enables facile aerobic functionalization of various PtIIMe complexes and some olefin hydroxo PtII complexes in hydroxylic solvents such as water and alcohols. Complexes LPtII(R)(HX) (L = dpms; R = Me, Ph; HX = H2O, MeOH, PhNH2) are oxidized by O2 to yield virtually quantitatively LPtIV(R)(X)(OH). Some of the derived PtIV alkyls LPtIV(Alk)(X)(OH) (X = OH, OMe) can reductively eliminate methanol in high yield. The mechanism of C-O elimination from LPtIV(Me)(X)(OH) (X = OH, OMe) in acidic aqueous media involves two concurrent pathways: an SN2 attack by water and an SN2 attack by a hydroxo or methoxo ligand of another PtIV species. In the latter case dimethyl ether is produced. The complex (dpms)Pt(ethylene)(OH) is oxidized by O2 in water to give a PtIV hydroxyethyl derivative that reductively eliminates ethylene oxide and ethylene glycol in aqueous solutions. The complexes derived from cyclic alkenes, cis-cyclooctene, norbornene, benzonorbornadiene, (dpms)PtII(cy-alkene)(OH), undergo olefin oxoplatination to give 1,2-oxaplatinacyclobutanes (PtII oxetanes). The derived PtII oxetanes are easily oxidized by O2 to produce PtIV oxetanes. The latter eliminate cleanly the corresponding epoxides by the mechanism of direct C(sp3)-O reductive eliminations, unprecedented in organoplatinum chemistry. The 1,2-azaplatinacyclobutanes (PtII azetidines) LPtII(CH2CH2NHR-&kappaC,&kappaN) (R = t-Bu, Me) are oxidized by O2 in the presence of acids to give PtIV azetidine complexes, [LPt(CH2CH2NHR-&kappaC,&kappaN)(OH)]+. The latter undergo reductive elimination of N-alkyl ethanolammonium salts, HOCH2CH2NH2R+, in acidic aqueous solutions at elevated temperatures. Efficient catalytic systems based on palladium acetate, di(6-pyridyl)ketone and 6-methyldi(2-pyridyl)methanesulfonate ligands, suitable for selective oxidation of ethylene with H2O2 to glycol acetates were developed. Glycol acetates were obtained in high selectivity and high yield on H2O2 under mild reaction conditions.
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    NEW LIGAND MOTIFS FOR PLATINUM-BASED `SHILOV CHEMISTRY' AND DETOURS INTO BASIC ORGANOMETALLIC RESEARCH
    (2009) Khaskin, Eugene; Vedernikov, Andrei N; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The C-H activation reaction at cationic platinum centers utilizing chelating aromatic N-type ligands has been widely studied in TFE (trifluoroethanol): a weakly coordinating solvent. In our laboratory, recent studies involving a modified dipyridine methane ligand revealed that benzene C-H activation in water, methanol and the activation of alkane substrates in TFE is possible. Anionic Pt(II) centers created via an anionic dipyridyl borate ligand present a new and promising direction towards realizing selective oxidation of alkanes. Rapid CH activation of alkanes and arenes is possible in biphasic water/hydrocarbon solvent mixtutes. In the course of CH activation studies with [dpbPtII(Me)2]- (dpb = di-2pyridyl-dimethyl-borate), the complex was found to yield olefin hydrides upon alkane activation. The yield of olefin hydride complexes with the dpb ligand proved low (30-40%). A lipophilic ligand (dtBupb = di-t-butylpyridyl-dimethyl-borate) activated various cyclic and linear olefins with near quantitative yields. The resultant olefin hydride complexes proved to be catalysts for transfer dehydrogenation of cyclic alkanes (TONs up to 13). We found that in the presence of a hydroxylic solvent, a very rapid oxidation of [dpbPtII(Me)2]- complex towards a PtIV species was observed. The proposed reaction mechanism includes rapid coordination of O2 by the highly electron-rich metal complex with subsequent nucleophiilic substitution reaction at boron and a methyl group transfer from the boron atom to the PtIV center. Oxidation with methyl iodide to give penta-coordinate dpbPtIVMe3 and its subsequent reaction with a hydroxylic solvent furnished the same product as under aerobic oxidation conditions. This proved that oxidation had to occur prior to methyl group transfer. Since in this case, our system can be considered as a mechanistic probe for Suzuki coupling, the insight into the nature of alkyl transfer provides a clear model of one the key steps of this widely-utilized transformation. Eventually, we were able to observe a reversible alkyl group transfer between PtIV and B in DMSO solutions. To probe the transfer of an aryl group between PtIV and B, a dpbPtIVMePh2 complex and a PtIVMe3 complex supported by (dpydphb = dipyridyl-diphenyl-borate) were synthesized. While phenyl transfer from PtIV to B was facile already in THF, the reverse, B-to-PtIV phenyl transfer was not observed due to the greater stabilization conferred to the complex by a B-Ph---PtIV moiety. The feasibility of a B-to-PtIV phenyl transfer was demonstrated when [dpydphbPtIIMe2] was oxidized by O2 in isopropanol.
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    Core/Shell and Alloy Nanoparticles of Transition Metals for Heterogeneous Catalysis: Bridging the Gap between Experiment and Theory
    (2008) Alayoglu, Selim; Eichhorn, Bryan W; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This thesis describes the structural and catalytic properties of the architecturally-controlled bimetallic nanoparticles (NPs) of transition metals. In this study, bimetallic nanoparticles with well-defined architectures were synthesized, characterized and evaluated toward various heterogeneous reactions. Random alloy nanoparticles were compared to the core/shell nanoparticles (M@M' NPs where M is the core metal and M' is the shell metal), which is the synthetic counterpart of the theoretically well-studied Near Surface Alloys (NSAs). Thus, the long existing experimental gap with the theory can be bridged via the systematic evaluation of such architecturally-controlled bimetallic NPs. The M@Pt (M=Ru, Rh, Ir, Pd and Au) and Ru@M' (M'=Rh and Pd) core/shell NPs of tunable core sizes and shell thicknesses, and the PtRu alloy and PtRh alloy NPs of various compositions were prepared via poly-ol reduction reactions by using sequential deposition techniques. Seed NPs for the core/shell systems were synthesized via either poly-ol or NaBH4 reduction reactions. The wet-chemical co-deposition technique was employed to synthesize the alloy NPs. The core/shell and alloy NPs were characterized by using a combination of TEM, STEM-EDS, XRD, and FT-IR and Micro Raman -CO probe experiments. Full structural analysis employing techniques such as Extended X-Ray Absorption Fine Structure (EXAFS) and atomic Pair Distribution Function (PDF) was also performed for the 4.1 nm Ru@Pt NPs comprising of 3.0 nm cores and 1-2 MLs thick shells and the 4.4 nm Pt50Ru50 alloy NPs. Through collaborations, the nanoparticle structures were also modeled through EXAFS analyses, PDF fits, Rietveld Refinements and Debye Function simulations. The well-characterized core/shell and alloy NPs were evaluated for preferential oxidation of CO in H2 feeds (PROX). Catalytically, the core/shell NPs were superior to their alloy counterparts with similar particle sizes and identical compositions. The PROX reactivities of the M@Pt (M=Ru, Rh, Ir, Pd and Au) core/shell NPs increased in the order of Au@Pt < Pd@Pt < Ir@Pt < Rh@Pt < Ru@Pt, which is predicted by the NSA theory. Density Functional Theory (DFT) calculations performed by Prof. Mavrikakis at the University of Wisconsin helped elucidate the thermo-chemistry beyond the enhanced PROX activities and the observed surface reactivity trends for the core/shell architectures. The decreased equilibrium surface coverage of CO as well as the new H2-assisted O2 dissociation pathway on the electronically-altered Pt shells were suggested to bring on the room temperature CO oxidation and the subsequent H2 activation with enhanced PROX selectivity. The surface reactivities toward PROX and benzene hydrogenation reactions of the composition series of the PtRu alloy NPs exhibited the `Volcano' behavior, which invoked the Hammer-Norskov theory. The preliminary benzene hydrogenation results on the Ru@Pt NPs system presented in this study also showed a structure dependent correlation in surface activity.
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    Living Coordinative Chain Transfer Polymerization of 1-Alkenes
    (2008-12-05) Zhang, Wei; Sita, Lawrence R.; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    A novel polymerization method, living coordinative chain transfer polymerization (CCTP), was recently developed with monocyclopentadienyl monoamidinate (CpAm) Group 4 metal complexes, which were previously applied for the traditional living coordination polymerization (TLCP) and stereomodulated degenerative transfer living (SDTL) coordination polymerization. In addition to a CpAm precatalyst and a cocatalyst, a chain transfer agent (CTA) was also added to the CCTP system. The CTA undergoes a rapid and reversible chain transfer with the Group 4 metal catalyst, which results in chain growth on an inexpensive main group metal alkyl. This new CCTP technique provides a practical solution towards the intrinsic problem, one chain per catalytic center, for a TLCP polymerization process. The first example of living CCTP was provided with ZnEt2 via Cp*HfMe2[N(Et)C(Me)N(Et)] (35) activated by [PhNHMe2][B(C6F5)4]. It was very efficient for the polymerization of ethene, propene, higher α-olefins and α,ω-nonconjugated dienes, and copolymerization of these monomers. The (co)polymers obtained possess very narrow polydispersity (PDI 1.03-1.10) and tunable molecular weights by several factors including a wide range of equivalents of ZnEt2. The living property of this CCTP system was further confirmed by kinetic studies and end group functionalization. The quantitative chain extension on zinc was clearly shown by in situ NMR spectroscopy. The coordinative chain shuttling polymerization (CCSP) was also studied while binary precatalysts, cocatalysts, or chain transfer agents were applied. The TLCP, SDTL and CCTP of propene via some new CpAm complexes other than 35 were also studied, including the zirconium analogue of 35, Cp*ZrMe2[N(Et)C(Me)N(Et)], and a series of binuclear complexes which have the common structure of [Cp*ZrMe2]2[N(tBu)C(Me)N(CH2)xNC(Me)N(tBu)] (26, x = 8; 27, x = 6; 28, x = 4). The formamidinate precatalyst Cp*ZrMe2[N(tBu)C(H)N(Et)] (12) was also covered in this study. Under both SDTL and CCTP conditions, the binuclear catalysts showed a tether-length dependent chain transfer process as observed by the polymerization results especially by the tacticity of resulting polypropene. Using CCSP process, multi-stereoblock polypropene was successfully prepared via 12 and 27. The structures and properties of these new complexes and (co)polymers were fully characterized by X-ray crystallography, elemental analysis, GPC, DSC, GC and high field NMR spectroscopy.
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    The Redox Chemistry of Dirhodium Carboxamidates: From Fundamental Structures to Catalytic Functions.
    (2008-03-24) Nichols, Jason M.; Doyle, Michael P.; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Redox chemistry is the study of molecular structure and function associated with changes in oxidation state. In this manuscript, the structures and functions of dinuclear rhodium complexes in various oxidation states are investigated. In Chapter 1, probing the structural chemistry of dirhodium(II) carboxamidates reveals that an unprecedented, stable, dirhodium(III) complex can be synthesized and characterized. Bis(σ-phenyl)-tetrakis(μ-caprolactamato)dirhodium(III) [Rh2(cap)4Ph2] was prepared from Rh2(cap)4 by a copper catalyzed, aerobic oxidation with aryl transfer from sodium tetraphenylborate. Structural data was obtained by single crystal X-ray diffraction (XRD) of Rh2(cap)4Ph2 and related structures with systematic changes in oxidation state. X-ray photoelectron spectroscopy (XPS) was used to determine binding energies for the rhodium electrons in the complexes. The structural data and XPS binding energies indicate that the Rh-Rh bonding interaction does not exist in Rh2(cap)4Ph2. In Chapter 2, the synthesis of Rh2(cap)4Ph2 was made general by using aryl-boronic acids as the aryl transfer agent. The synthesis provided access to an array of bis(σ-aryl)-Rh2L4 complexes with varying substitution of the aryl ligands. X-ray structures, electrochemical, and computational analysis of complexes with substituents of varying electron-deficiency confirm the Rh Rh bond cleavage. A second-order Jahn-Teller effect is proposed as the basis for the observed Rh-Rh-C bond angle distortions in the X-ray crystal structures. The delocalization of the aromatic π-system through the Rh2-core was investigated and found to be absent, consistent with the calculated electronic structure. The final chapter explores the catalytic redox chemistry of Rh2(cap)4. The mechanism for the oxidative Mannich reaction catalyzed by Rh2(cap)4 in conjunction with tert-butyl hydroperoxide was investigated. This study revealed that iminium ions were formed by the oxidation of N,N-dialkylanilines with the Rh2(cap)4/TBHP system. Rh2(cap)4 was found to be a catalyst for the homolytic decomposition of TBHP to yield the tert-butylperoxyl radical (t BuOO) in a one-electron redox couple. Iminium ions were formed in a stepwise process from N,N-dialkylaniline via rate-limiting, hydrogen atom transfer to t-BuOO followed by rapid electron transfer to excess oxidant in situ. The net hydrogen atom transfer was found to be a step-wise electron transfer/proton transfer between the N,N-dialkylaniline and t BuOO providing evidence for a novel reactivity mode for peroxyl radicals. Nucleophilic capture of the iminium ion to complete the Mannich process was found to occur without association to Rh2(cap)4 under thermodynamic control.
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    ELECTROCHEMICAL OXIDATION KINETICS OF HYDROGEN AND HIGHER HYDROCARBON FUELS ON SOLID OXIDE FUEL CELLS.
    (2007-11-27) Demircan, Oktay; Eichhorn, Bryan W; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Solid oxide fuel cells (SOFCs) are promising electrochemical energy converting devices due to their ability to use not only hydrogen but also hydrocarbons as a fuel. Although conventional SOFCs with Ni/YSZ anodes and hydrocarbon fuels form carbon deposits that inhibit SOFC performance, an enhancement in performance is observed for the Cu/CeO2/YSZ anode with carbon deposits and H2 fuel. Structural and compositional analyses of these carbon deposits show that graphitic carbon forms on the Cu/CeO2/YSZ. The reason of the 2 to 3 fold enhancement in performance is due to increase in anode conductivity by graphitic carbon deposits. An important problem for fuel oxidation kinetics on SOFC anodes is determining the rate limiting step(s) for fuel oxidation. To assess the effects of YSZ surface chemistry on oxidation processes, porous and dense Au anodes on YSZ electrolytes were prepared to study H2 oxidation. Linear Sweep Voltammetry (LSV) and Electrochemical Impedance Spectroscopy (EIS) were used to identify critical processes in the Au/YSZ anodes as a function of Au geometry. The results show that the surface diffusion on the SOFC anodes and electrolytes is believed most likely to be the rate limiting step. To address the contribution of reduced YSZ on SOFC anode performance, porous Au anodes with different geometrical porous YSZ layers were fabricated. Studies of porous YSZ layers on Au anodes demonstrate that these layers block active sites on Au anodes for dissociative adsorption of hydrogen but help charge transfer reaction of adsorbed species on anode. Other than regular hydrogen as a fuel, isotopically-labeled D2 fuel were used to differentiate effects of both gas phase and surface diffusion on Au anode performance. An observed ~25 % decrease in current and power densities with D2 relative to H2 is attributed to lower surface diffusion of adsorbed D2 fuel species relative to H2 fuel species. Finally, modeling studies for these systems are used to understand more fully the mechanisms of H2 oxidation on SOFC anodes. The interpretations of experimental results are confirmed by using the model that manipulates the effect of various fuel partial pressures on the diffusion parameters of anode surface species. The model developed is able to describe qualitatively the isotope effect on the gas and surface diffusion coefficients by the mass affect. The implementation of the surface diffusion parameters of the water species into this model is critical to manipulate the effect of the fuel partial pressure values on diffusion processes.
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    Architecturally Controlled Bimetallic Nanoparticles for Heterogeneous Catalysis
    (2007-03-28) Zhou, Shenghu; Eichhorn, Bryan; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    This work develops synthetic methods for architecturally controlled AuPt and CuPt bimetallic nanomaterials. The AuPt heteroaggregate, AuPt alloy spherical nanoparticles, and AuPt alloy nanowires were prepared by a sequential or co-reduction method. The unique AuPt heteroaggregate nanostructures, synthesized by the sequential reduction method, contain Au cores with Pt tendrils extending from the Au surfaces. The AuPt alloy nanoparticles or nanowires were prepared by the rapid co-reduction method. This rapid co-reduction method prevents the phase separation and traps the metastable AuPt alloy phase. The AuPt heteroaggregate, alloy spherical nanoparticles, alloy nanowires, and the reported Au@Pt core-shell structures, constitute the rare example of a bimetallic system containing all reported architectures in the literature. Kinetically stabilized Cu@Pt core-shell nanoparticles were prepared by deposition of Pt onto Cu nanoparticles. The Cu@Pt particles exhibit high stability toward alloying upon annealing. In contrast, the Pt@Cu particles readily transform into alloy structures in the same conditions. This abnormal stability of the Cu@Pt particles is attributed to the Kirkendall mass transport effect, where the inherent diffusion direction from the Pt to Cu is hindered by a limited population of vacancies in the Cu cores. These architecturally controlled bimetallic nanomaterials were applied in CO tolerant hydrogen oxidation and de-NOx reactions with hydrogen. In the H2/CO/O2 fuel, the AuPt alloy nanoparticles are CO tolerant in hydrogen oxidation, and the AuPt heteroaggregate nanoparticles exhibit enhanced preferential CO oxidation in the presence of Fe promoters. In the NO/H2 reaction, the Cu@Pt nanoparticles maintain the high activity of pure Pt particles and have a higher selectivity for N2. Under 4/1 H2/NO conditions, the selectivity for N2 over the Cu@Pt catalyst is 45%. In contrast, under the same conditions, the pure Pt catalyst exhibits a selectivity of 22%. The Pt@Pd catalyst enhances activity as well as selectivity due to the near surface alloy effect.