The Experts below are selected from a list of 32733 Experts worldwide ranked by ideXlab platform
Younan Xia - One of the best experts on this subject based on the ideXlab platform.
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photochemical deposition of highly dispersed Pt Nanoparticles on porous ceo2 nanofibers for the water gas shift reaction
Advanced Functional Materials, 2015Co-Authors: Botao Qiao, Younan Xia, Dong Choon Hyun, Jinguo Wang, Moon J Kim, Jingyue LiuAbstract:Ceria (CeO2) nanofibers with high porosity are fabricated using an approach involving sol–gel, electrospinning, and calcination. Specifically, cerium(III) acetylacetonate and polyacrylonitrile (PAN) are dissolved in N,N-dimethylformamide (DMF) and then electrospun into nanofibers. The PAN matrix plays a critical role in stabilizing the porous structure from collapse during calcination in air up to 800 °C. CeO2 porous nanofibers comprising an interconnected network of single crystalline and fully oxidized CeO2 Nanoparticles about 40 nm in size are obtained. The hierarchically porous structure of the CeO2 nanofibers enables the facile deposition of Pt Nanoparticles via heterogeneous nucleation in a photochemical method. When conducted in the presence of poly(vinyl pyrrolidone) (PVP) and 4-benzyolbenzoic acid, uniform Pt Nanoparticles with an average diameter of 1.7 nm are obtained, which are evenly dispersed across the entire surface of each CeO2 nanofiber. The high porosity of CeO2 nanofibers and the uniform distribution of Pt Nanoparticles greatly improve the activity and stability of this catalytic system toward the water-gas shift reaction. It is believed that this method could be extended to produce a variety of catalysts and systems sought for various industrial applications.
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functionalization of electrospun tio2 nanofibers with Pt Nanoparticles and nanowires for catalytic applications
Nano Letters, 2008Co-Authors: Eric Formo, Eric Lee, Dean Campbell, Younan XiaAbstract:This paper reports a simple procedure for derivatizing the surface of anatase TiO2 nanofibers with Pt Nanoparticles and then Pt nanowires. The nanofibers were prepared in the form of a nonwoven mat by electrospinning with a solution containing both poly(vinyl pyrrolidone) and titanium tetraisopropoxide, followed by calcination in air at 510 degrees C. The fiber mat was then immersed in a polyol reduction bath to coat the surface of anatase fibers with Pt Nanoparticles of 2-5 nm in size with controllable density of coverage. Furthermore, the coated fibers could serve as a three-dimensional scaffold upon which Pt nanowires of roughly 7 nm in diameter could be grown at a high density and with a length up to 125 nm. The fiber membranes functionalized with Pt Nanoparticles and nanowires are interesting for a number of catalytic applications. It was found to show excellent catalytic activity for the hydrogenation of azo bonds in methyl red, which could be operated in a continuous mode by passing the dye solution through the membrane at a flow rate of 0.5 mL/s.
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pd catalyzed growth of Pt Nanoparticles or nanowires as dense coatings on polymeric and ceramic particulate supports
Advanced Materials, 2006Co-Authors: Eric Lee, Jingyi Chen, Yadong Yin, Charles T Campbell, Younan XiaAbstract:This Communication describes an approach that can control the growth of Pt into shells that consist of Nanoparticles or nanowires on colloidal spheres. Core/shell particles have been extensively studied largely because of their attractive properties (oPtical, mechanical, magnetic, or catalytic) that are often different from their bulk counterparts. As a result of their unique features, core/shell particles hold promise in potential applications such as controlled delivery, catalysis, magnetic information storage, oPtical sensing, and confinement of reactions. Many research efforts have been directed towards the development of new techniques for “engineering” such materials with well-controlled properties. In general, the properties of core/shell particles can be tailored precisely by varying the composition, dimension, and structure of the cores or shells. One-dimensional (1D) nanostructures, especially nanowires, have attracted much attention due to their potential use as interconnects in fabricating electronic devices. However, with respect to the procedure and cost effectiveness, producing nanowires is far from being trivial. It remains a grand challenge to develop a plausible method for generating large quantities of nanowires from various metals. Here we present a versatile approach capable of generating core/ shell particles, with the cores being polymer or silica beads and the shells being dense, uniform coatings of Pt Nanoparticles or quasiradial Pt nanowires. We recently discovered that the introduction of a trace amount of iron species (Fe or Fe) to the polyol process could induce the formation of Pt nanowires or multipods by significantly reducing the net reduction rate of the salt precursor. We have also shown that these nanowires could be catalytically activated to grow from the surface of micrometersized aggregates consisting of Pt Nanoparticles. Herein, we demonstrate a more affordable and practical method for growing Pt nanowires by using Pd-coated colloidal spheres to imitate the catalytic property of the Pt aggregates. Moreover, this procedure can be modified to grow thick, uniform shells composed of Pt Nanoparticles. The key to the success of these syntheses are Pd Nanoparticles (2–4 nm in size) that can be readily generated in situ as sub-monolayers on colloidal spheres terminated by an amino functional group by reducing a palladium precursor with ethanol under sonication. No growth of Pt Nanoparticles or nanowires was observed when there were no Pd Nanoparticles on the surface of the colloidal spheres. We note that such Pd Nanoparticles have been widely used as a catalyst in the electroless deposition of thin films of metals such as Ni, Cu, and Ag on various substrates. In the present work, Pt nanowires with aspect ratios of up to 30 could be controllably grown through an iron-mediated polyol reduction when there was a catalytic metal exposed on the substrate surface. Furthermore, shells of Pt Nanoparticles with thicknesses of up to 100 nm could be formed by reducing the amount of iron species added to the reaction solution. Figure 1 illustrates the multistep protocol designed to grow Pt Nanoparticles or nanowires as thick coatings on colloidal spheres. In the first step, amino-functionalized melamine beads were sonicated in a solution of [PdCl4] 2– and ethanol for 1 h, resulting in the direct attachment of Pd Nanoparticles to the polymer surface as a sub-monolayer (product A in Fig. 1). Here, ethanol acts as a reducing agent to produce Pd from Pd. The amino-terminated coupling agents on the substrate surface might also act as a primer to attract the Pd Nanoparticles, which nucleated in the solution phase. Dokoutchaev et al. have reported that the surface of amino-derivatized polymer beads showed a large affinity for Pd Nanoparticles. The resulting beads were recovered from the reaction solution by centrifugation and washed several times with ethanol and water. In the next step, the Pd-coated beads were dispersed in ethylene glycol (EG) and heated to 110 °C. After heating for 1 h to activate the immobilized Pd Nanoparticles and to decompose some EG to aldehyde, specific amounts of H2PtCl6/EG and poly(vinyl pyrrolidone)/EG (PVP/EG) were added dropwise to the reaction solution. At this stage, H2PtCl6 was reduced by the aldehyde to form a Pt II intermediate, which could remain in this state at room temperature for more than one month without being reduced further to Pt. The solution was continuously heated for another 2 h (or until the solution turned yellow-green) to ensure C O M M U N IC A IO N
Yusuke Yamauchi - One of the best experts on this subject based on the ideXlab platform.
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polymeric micelle assembly for the direct synthesis of functionalized mesoporous silica with fully accessible Pt Nanoparticles toward an improved co oxidation reaction
Chemical Communications, 2014Co-Authors: Bishnu Prasad Bastakoti, Yusuke Yamauchi, Nobuyoshi Miyamoto, Noelia M Sanchezballester, Hideki Abe, Pavuluri SrinivasuAbstract:Pt-decorated mesoporous silica is directly prepared using a polymeric micelles assembly approach using an asymmetric triblock copolymer, poly(styrene-b-2-vinylpyridine-b-ethylene oxide) as the structure directing agent. Strongly immobilized, fully accessible, and uniformly dispersed Pt Nanoparticles on mesoporous silica wall exhibit superior catalytic activity toward CO oxidation.
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all metal mesoporous nanocolloids solution phase synthesis of core shell pd Pt Nanoparticles with a designed concave surface
Angewandte Chemie, 2013Co-Authors: Hamed Ataeeesfahani, Yusuke Yamauchi, Masataka ImuraAbstract:Colloidal Pd@Pt Nanoparticles with uniform mesopores can be synthesized in one step by a facile solution-phase method involving slow reduction of metal species in strong acidic media. In this system, F127 micelles can directly act as a template to form the mesopores in the product, and the greater reducibility of the Pd species leads to the desired core-shell Pd@Pt nanocolloids.
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synthesis of mesoporous Pt Nanoparticles with uniform particle size from aqueous surfactant solutions toward highly active electrocatalysts
Chemistry: A European Journal, 2011Co-Authors: Liang Wang, Yusuke YamauchiAbstract:: Pores for improved catalysis: Mesoporous Pt Nanoparticles (MPNs) with large surface areas are created within 10 min by a very simple, one-step, aqueous reaction at room temperature. The obtained MPNs exhibit significantly enhanced catalytic activity toward the methanol oxidation reaction.
Nguyen Viet Long - One of the best experts on this subject based on the ideXlab platform.
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synthesis and characterization of polyhedral and quasi sphere non polyhedral Pt Nanoparticles effects of their various surface morphologies and sizes on electrocatalytic activity for fuel cell applications
Journal of Nanoparticle Research, 2011Co-Authors: Nguyen Viet Long, Michitaka Ohtaki, Tong Duy Hien, Randy Jalem, Masayuki NogamiAbstract:In this article, polyhedral and non-polyhedral Pt Nanoparticles were prepared by modified polyol method using AgNO3 as a good structure-modifying agent. Their TEM and HRTEM images showed the particle size in the range of 8–16 nm for both the above cases. The structures and properties of the surfaces of Pt Nanoparticles were investigated through cyclic voltammetry in dilute perchloric acid (HClO4) electrolyte solution. A comparison of the electrocatalytic property in methanol electrooxidation was made. Here, the effects of polyhedral and non-polyhedral morphologies on their catalytic properties were studied. The results revealed that the special catalytic activity of quasi-sphere non-polyhedral Pt Nanoparticles is higher than that of polyhedral Pt Nanoparticles. In addition, Pt Nanoparticles of un-sharp and quasi-sphere morphologies exhibit the tolerance to poisoning species better than that of Pt Nanoparticles of sharp and polyhedral morphologies due to the various morphologies of the catalyst surfaces in the chronoamperometric plots. Therefore, these experimental evidences showed the morphology-dependent catalytic property according to the various morphologies and complexity of their catalyst surfaces.
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synthesis and characterization of polyhedral Pt Nanoparticles their catalytic property surface attachment self aggregation and assembly
Journal of Colloid and Interface Science, 2011Co-Authors: Nguyen Viet Long, Michitaka Ohtaki, Randy Jalem, Masaya Uchida, Hirohito Hirata, Nguyen Duc Chien, Masayuki NogamiAbstract:Abstract In this paper, we presented the preparation procedure of Pt Nanoparticles with the well-controlled polyhedral morphology and size by a modified polyol method using AgNO3 in accordance with the reduction of H2PtCl6 in EG at high temperature around 160 °C. The methods of UV–vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and high resolution (HR) TEM measurements were used to characterize their surface morphology, size, and crystal structure. We have observed that the polyhedral Pt Nanoparticles of sharp edges and corners were produced in the preferential homogenous growth as well as the formation of porous and large Pt particles by self-aggregation and assembly originating from as-prepared polyhedral Pt Nanoparticles. It is most impressive to find that the arrangement of Pt Nanoparticles was observed in their surface attachments, self-aggregation, random and directed surface self-assembly by the bottom-up approach. Their high electrocatalytic activity for methanol oxidation was predicted. The findings and results showed that the polyhedral Pt nanoparticle-based catalysts exhibited the high electrocatalytic activity for their potential applications in developing the efficient Pt-based catalysts for direct methanol fuel cells.
Peng Wu - One of the best experts on this subject based on the ideXlab platform.
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Pt Nanoparticles entrapped in ordered mesoporous carbons an efficient catalyst for the liquid phase hydrogenation of nitrobenzene and its derivatives
Chinese Journal of Catalysis, 2015Co-Authors: Junrui Li, Xiaohong Li, Yue Ding, Peng WuAbstract:Abstract Pt Nanoparticles entrapped in ordered mesoporous CMK-3 carbons with p6mm symmetry were prepared using a facile impregnation method, and the resulting materials were characterized using X-ray diffraction spectroscopy, N2 adsorPtion-desorPtion, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The Pt Nanoparticles were highly dispersed in the CMK-3 with 43.7% dispersion. The Pt/CMK-3 catalyst was an effective catalyst for the liquid-phase hydrogenation of nitrobenzene and its derivatives under the experimental conditions studied here. The Pt/CMK-3 catalyst was more active than commercial Pt/C catalyst in most cases. A highest turnover frequency of 43.8 s−1 was measured when the Pt/CMK-3 catalyst was applied for the hydrogenation of 2-methyl-nitrobenzene in ethanol under oPtimal conditions. It is worthy of note that the Pt/CMK-3 catalyst could be recycled easily, and could be reused at least fourteen times without any loss in activity or selectivity for the hydrogenation of nitrobenzene in ethanol.
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Pt Nanoparticles entrapped in ordered mesoporous carbons for liquid phase hydrogenation of unsaturated compounds
Catalysis Communications, 2012Co-Authors: Yue Ding, Xiaohong Li, Bo Li, Haihong Wang, Peng WuAbstract:Abstract Pt Nanoparticles entrapped in ordered mesoporous carbons were proved effective for liquid-phase hydrogenation of benzaldehyde and its derivatives in water. Due to higher hydrophobicity, Pt/CMK-3 catalyst was slightly superior to Pt/CMK-8 catalyst towards benzaldehyde hydrogenation. Nevertheless, the larger pore volume of Pt/CMK-8 catalyst is more beneficial for mass transfer of benzaldehyde derivatives. In addition, the surface electronic state of Pt particles deposited on CMK-8 is helpful for the activation of carbonyl compounds. Therefore, the Pt/CMK-8 and Pt/CMK-3 catalysts showed tiny differences in most cases. The Pt catalysts can also catalyze the hydrogenation of olefins and other carbonyl compounds.
Masayuki Nogami - One of the best experts on this subject based on the ideXlab platform.
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synthesis and characterization of polyhedral and quasi sphere non polyhedral Pt Nanoparticles effects of their various surface morphologies and sizes on electrocatalytic activity for fuel cell applications
Journal of Nanoparticle Research, 2011Co-Authors: Nguyen Viet Long, Michitaka Ohtaki, Tong Duy Hien, Randy Jalem, Masayuki NogamiAbstract:In this article, polyhedral and non-polyhedral Pt Nanoparticles were prepared by modified polyol method using AgNO3 as a good structure-modifying agent. Their TEM and HRTEM images showed the particle size in the range of 8–16 nm for both the above cases. The structures and properties of the surfaces of Pt Nanoparticles were investigated through cyclic voltammetry in dilute perchloric acid (HClO4) electrolyte solution. A comparison of the electrocatalytic property in methanol electrooxidation was made. Here, the effects of polyhedral and non-polyhedral morphologies on their catalytic properties were studied. The results revealed that the special catalytic activity of quasi-sphere non-polyhedral Pt Nanoparticles is higher than that of polyhedral Pt Nanoparticles. In addition, Pt Nanoparticles of un-sharp and quasi-sphere morphologies exhibit the tolerance to poisoning species better than that of Pt Nanoparticles of sharp and polyhedral morphologies due to the various morphologies of the catalyst surfaces in the chronoamperometric plots. Therefore, these experimental evidences showed the morphology-dependent catalytic property according to the various morphologies and complexity of their catalyst surfaces.
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synthesis and characterization of polyhedral Pt Nanoparticles their catalytic property surface attachment self aggregation and assembly
Journal of Colloid and Interface Science, 2011Co-Authors: Nguyen Viet Long, Michitaka Ohtaki, Randy Jalem, Masaya Uchida, Hirohito Hirata, Nguyen Duc Chien, Masayuki NogamiAbstract:Abstract In this paper, we presented the preparation procedure of Pt Nanoparticles with the well-controlled polyhedral morphology and size by a modified polyol method using AgNO3 in accordance with the reduction of H2PtCl6 in EG at high temperature around 160 °C. The methods of UV–vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and high resolution (HR) TEM measurements were used to characterize their surface morphology, size, and crystal structure. We have observed that the polyhedral Pt Nanoparticles of sharp edges and corners were produced in the preferential homogenous growth as well as the formation of porous and large Pt particles by self-aggregation and assembly originating from as-prepared polyhedral Pt Nanoparticles. It is most impressive to find that the arrangement of Pt Nanoparticles was observed in their surface attachments, self-aggregation, random and directed surface self-assembly by the bottom-up approach. Their high electrocatalytic activity for methanol oxidation was predicted. The findings and results showed that the polyhedral Pt nanoparticle-based catalysts exhibited the high electrocatalytic activity for their potential applications in developing the efficient Pt-based catalysts for direct methanol fuel cells.
