The Experts below are selected from a list of 7986 Experts worldwide ranked by ideXlab platform
Jeffrey T Miller - One of the best experts on this subject based on the ideXlab platform.
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aqueous phase glycerol reforming with pt and ptmo Bimetallic Nanoparticle catalysts the role of the mo promoter
Topics in Catalysis, 2013Co-Authors: Paul J Dietrich, Tianpin Wu, Aslihan Sumer, James A Dumesic, Julius Jellinek, Nicholas W Delgass, Fabio H Ribeiro, Jeffrey T MillerAbstract:The turnover rate (TOR, normalized to sites measured by CO chemisorption before reaction) and selectivity for the aqueous phase reforming of glycerol have been determined for Pt/C and PtMo/C catalysts. While the TOR of PtMo/C is higher than that of Pt/C by about 4 times at comparable conversion, the selectivity to C–O bond cleavage is higher, thus reducing the H2 yield at high conversion. Under reaction conditions on Pt/C, CO is observed as the most abundant Pt surface species with a fractional coverage of about 0.6 using operando X-ray absorption spectroscopy. Since there is little CO in the effluent (CO2:CO ratios > 100:1, when CO is detected), it is thought that surface CO is converted to H2 and CO2 by the water gas shift reaction. DFT calculations suggest that the role of metallic Mo is to alter the electronic properties of Pt lowering the binding energy of CO and reducing the activation energies of dehydrogenation and C–O bond cleavage. Because the activation energy for C–O cleavage is lowered more than for dehydrogenation, the selectivity for C–O bond cleavage is increased, ultimately lowering the H2 yield compared to Pt/C.
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in situ x ray absorption spectroscopic analysis of gold palladium Bimetallic Nanoparticle catalysts
ACS Catalysis, 2013Co-Authors: Aimee Maclennan, Jeffrey T Miller, Abhinandan Banerjee, Yongfeng Hu, Robert W J ScottAbstract:Gold–palladium core–shell Nanoparticles have been previously shown to be extremely effective catalysts for a number of oxidation reactions including the aerobic oxidation of alcohols. However, the novel activity and durability of such catalysts are still poorly understood, and there are several putative mechanisms by which oxidation reactions can proceed. Previously we showed that Pd(II) salts in the presence of Au Nanoparticles were also effective catalysts for the room temperature oxidation of crotyl alcohol. Herein we show an in situ X-ray absorption spectroscopy (XAS) study at both the Pd–K and Pd-LIII edges of Au Nanoparticle/Pd(II) salt solutions in the presence of crotyl alcohol. Liquid cells with X-ray permeable windows were used to obtain quick-scan XAS data during the oxidation of crotyl alcohol, allowing for time-resolved Pd speciation information and information about the reaction mechanism and kinetics. XAS measurements definitively show that the first step of this reaction involves Pd reduct...
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supported ru pt Bimetallic Nanoparticle catalysts prepared by atomic layer deposition
Nano Letters, 2010Co-Authors: Steven T Christensen, Jeffrey T Miller, Hao Feng, Joseph L Libera, Peter C Stair, Jeffrey W ElamAbstract:Atomic layer deposition (ALD) is used to deposit ruthenium−platinum nanostructured catalysts using 2,4-(dimethylpentadienyl)(ethylcyclopentadienyl) ruthenium, trimethyl(methylcyclopentadienyl) platinum, and oxygen as precursors. Transmission electron microscopy shows discrete 1.2 nm Nanoparticles decorating the surface of the spherical alumina support. The Ru−Pt particles are crystalline and have a crystal structure similar to pure platinum. X-ray fluorescence measurements show that the Nanoparticle composition is controlled by the ratio of metal precursor ALD cycles. X-ray absorption spectroscopy at the Ru K-edge indicates a nearest neighbor Ru−Pt interaction consistent with a Bimetallic composition. Methanol decomposition reactions further confirm a Ru−Pt interaction and show enhanced methanol conversion for the Bimetallic Nanoparticles when compared to catalysts comprised of a mixture of pure Pt and Ru Nanoparticles of similar loading. These results demonstrate that ALD is a viable technique for synthe...
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cleaner water using Bimetallic Nanoparticle catalysts
Journal of Chemical Technology & Biotechnology, 2009Co-Authors: Michael S Wong, Pedro J J Alvarez, Yulun Fang, Nurgul Akcin, Michael O Nutt, Jeffrey T Miller, Kimberly N HeckAbstract:Groundwater contaminated by hazardous chlorinated compounds, especially chlorinated ethenes, continues to be a significant environmental problem in industrialized nations. The conventional treatment methods of activated carbon adsorption and air-stripping successfully remove these compounds by way of transferring them from the water phase into the solid or gas phase. Catalysis is a promising approach to remove chlorinated compounds completely from the environment, by converting them into safer, non-chlorinated compounds. Palladium-based materials have been shown to be very effective as hydrodechlorination catalysts for the removal of chlorinated ethenes and other related compounds. However, relatively low catalytic activity and a propensity for deactivation are significant issues that prevent their widespread use in groundwater remediation. Palladiumon-gold Bimetallic Nanoparticles, in contrast, were recently discovered to exhibit superior catalyst activity and improved deactivation resistance. This new type of material is a significant next-step in the development of a viable hydrodechlorination catalysis technology. c � 2008 Society of Chemical Industry
Michael S Wong - One of the best experts on this subject based on the ideXlab platform.
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cleaner water using Bimetallic Nanoparticle catalysts
Journal of Chemical Technology & Biotechnology, 2009Co-Authors: Michael S Wong, Pedro J J Alvarez, Yulun Fang, Nurgul Akcin, Michael O Nutt, Jeffrey T Miller, Kimberly N HeckAbstract:Groundwater contaminated by hazardous chlorinated compounds, especially chlorinated ethenes, continues to be a significant environmental problem in industrialized nations. The conventional treatment methods of activated carbon adsorption and air-stripping successfully remove these compounds by way of transferring them from the water phase into the solid or gas phase. Catalysis is a promising approach to remove chlorinated compounds completely from the environment, by converting them into safer, non-chlorinated compounds. Palladium-based materials have been shown to be very effective as hydrodechlorination catalysts for the removal of chlorinated ethenes and other related compounds. However, relatively low catalytic activity and a propensity for deactivation are significant issues that prevent their widespread use in groundwater remediation. Palladiumon-gold Bimetallic Nanoparticles, in contrast, were recently discovered to exhibit superior catalyst activity and improved deactivation resistance. This new type of material is a significant next-step in the development of a viable hydrodechlorination catalysis technology. c � 2008 Society of Chemical Industry
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improved pd on au Bimetallic Nanoparticle catalysts for aqueous phase trichloroethene hydrodechlorination
Applied Catalysis B-environmental, 2006Co-Authors: Michael O Nutt, Pedro J J Alvarez, Kimberly N Heck, Michael S WongAbstract:Abstract Groundwater remediation through the catalytic breakdown of the undesired contaminants is a more effective and desirable approach than the conventional physical displacement methods of air-stripping and carbon adsorption. Palladium-on-gold Nanoparticles (Pd/Au NPs) have recently been shown to catalyze the hydrodechlorination of trichloroethene in water, at room temperature, and in the presence of hydrogen, with the most active Pd/Au material found to be >70 times more active than Pd supported on alumina on a per-Pd atom basis. The potential of this catalyst as a groundwater remediation technology could be improved by synthesizing Pd/Au NPs with smaller diameters and immobilizing them on a solid support. For this study, we synthesized Pd/Au NPs with a core diameter of 4 nm and with different Pd loadings and studied them in colloidal form for aqueous-phase trichloroethene hydrodechlorination. The most active catalysts were considerably more active (>1900 L/gPd/min) than Pd NPs (55 L/gPd/min) and conventionally synthesized Pd/Al2O3 (47 L/gPd/min). Accounting for a gas–liquid mass transfer effect and converting the Pd loading to Pd surface coverage using a magic cluster model for the Pd/Au NPs, the reaction rates in terms of initial turnover frequencies were >1.4, 4.35 × 10−2, and 3.76 × 10−2 s−1, respectively. These materials exhibited volcano-like catalytic activity, in which hydrodechlorination rate was maximum near 70% Pd surface coverage. Au appeared to promote catalysis through geometric and electronic effects. Immobilization of the NPs on alumina, magnesia, and silica supports yielded active oxide-supported catalysts.
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designing pd on au Bimetallic Nanoparticle catalysts for trichloroethene hydrodechlorination
Environmental Science & Technology, 2005Co-Authors: Michael O Nutt, Joseph B Hughes, Michael S WongAbstract:Alumina-supported palladium (Pd) catalysts have previously been shown to hydrodechlorinate trichloroethene (TCE) and other chlorinated compounds in water, at room temperature, and in the presence of hydrogen. The feasibility of this catalytic technology to remediate groundwater of halogenated compounds can be improved by re-designing the Pd material in order to increase catalytic activity. We synthesized and characterized Pd supported on gold Nanoparticles (Au NPs) of different Pd loadings. In all cases, we found that these catalysts were considerably more active than Pd NPs, alumina-supported Pd, and Pd-black (62.0, 12.2, and 0.42 L·gPd-1·min-1, respectively). There is a synergistic effect of the Pd-on-Au Bimetallic structure, with the material with the highest TCE hydrodechlorination activity (943 L·gPd-1·min-1) comprised of Au NPs partially covered by Pd metal. The Pd-on-Au Bimetallic catalyst structure provides a new synthesis approach in improving the catalytic properties of monometallic Pd materials...
Khalil Abdelrazek Khalil - One of the best experts on this subject based on the ideXlab platform.
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nicu Bimetallic Nanoparticle decorated graphene as novel and cost effective counter electrode for dye sensitized solar cells and electrocatalyst for methanol oxidation
Applied Catalysis A-general, 2015Co-Authors: Moaaed Motlak, Nasser A M Barakat, Ahmed G Eldeen, A M Hamza, M Obaid, Bong O Yang, Shaheer M Akhtar, Khalil Abdelrazek KhalilAbstract:Abstract NiCu Bimetallic Nanoparticle-decorated graphene was prepared by hydrothermal treatment to be utilized as an efficient and alternative Pt-free counter electrode (CE) for dye-sensitized solar cells (DSSCs). The results indicated that the performance of the introduced modified graphene as CE strongly depends on the composition of the metallic Nanoparticles. Typically, Ni-, Ni 0.25 Cu 0.75 -, Ni 0.6 Cu 0.4 - and Ni 0.75 Cu 0.25 -decorated graphene were synthesized. Investigation of the electrochemical characteristics indicated that the graphene decorated by Ni 0.75 Cu 0.25 Nanoparticles shows the highest catalytic activity and conductivity compared to the other prepared formulations as well as pristine graphene. In DSSC, Ni 0.75 Cu 0.25 Nanoparticle-decorated graphene can remarkably improve the catalytic activity toward triiodide reduction and lower the resistance at the electrolyte–CE interface. Accordingly, the obtained energy conversion efficiencies were 1.72%, 2.39%, 1.24%, 2.87% and 5.1% for pristine, Ni-, Ni 0.25 Cu 0.75 -, Ni 0.6 Cu 0.4 - and Ni 0.75 Cu 0.25 -decorated graphene, respectively. The obtained efficiency for Ni 0.75 Cu 0.25 -decorated graphene is comparable with Pt-based DSSC fabricated by the same procedure (5.9%) which recommends exploiting the introduced modified graphene as efficient and cost-effective CE for the large-scale fabrication of photovoltaic devices. The catalytic performance of the best formulation was examined toward methanol electrooxidation; the results indicated effective and stable electrocatalytic activity.
Gnana G Kumar - One of the best experts on this subject based on the ideXlab platform.
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green synthesis of pt pd Bimetallic Nanoparticle decorated reduced graphene oxide and its robust catalytic activity for efficient ethylene glycol electrooxidation
New Journal of Chemistry, 2018Co-Authors: Raj T Kumar, Gnana G KumarAbstract:A simple one-pot green synthesis method is developed to prepare a platinum–palladium (Pt–Pd) Bimetallic Nanoparticle decorated reduced graphene oxide (rGO) nanocomposite using vermicast extract as a reducing and stabilization agent. Morphological analysis confirms the homogenous decoration of Pt–Pd Nanoparticles over the rGO sheets. Structural studies verify that the fatty acids and amide groups of the vermicast extract play a foremost role in the reduction of graphene oxide (GO) and the metallic ions. Benefiting from Bimetallic features and a precise carbon support, the dehydrogenation of ethylene glycol (EG) and CO tolerance toward EG oxidation is significantly enhanced for rGO/Pt–Pd. The enhanced electrocatalytic activity of rGO/Pt–Pd toward EG oxidation is quantified via its mass activity of 803.4 mA mg−1, which is higher than the prepared nanocatalysts and commercial Pt/C. Furthermore, rGO/Pt–Pd retains a high current density (85%) over 500 cycles from its initial value, revealing its robust tolerance against CO poisoning. Thus the adopted green approach affords a cost-efficient and biocompatible carbonaceous metal nanocomposite with desirable electrocatalytic activity and stability for EG electrooxidation, demonstrating its wide applicability in high performance energy conversion devices.
Ruo Yuan - One of the best experts on this subject based on the ideXlab platform.
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electrochemistry of cholesterol biosensor based on a novel pt pd Bimetallic Nanoparticle decorated graphene catalyst
Talanta, 2013Co-Authors: Lei Zhang, Yaqin Chai, Ruo YuanAbstract:Abstract A new electrochemical biosensor with enhanced sensitivity was developed for detection of cholesterol by using platinum–palladium–chitosan–graphene hybrid nanocomposites (PtPd–CS–GS) functionalized glassy carbon electrode (GCE). An electrodeposition method was applied to form PtPd Nanoparticles-doped chitosan–graphene hybrid nanocomposites (PtPd–CS–GS), which were characterized by scanning electron microscopy (SEM) and electrochemical methods. The presence of the PtPd–CS–GS nanocomposites not only accelerated direct electron transfer from the redox enzyme to the electrode surface, but also enhanced the immobilized amount of cholesterol oxidase (ChOx). Under optimal conditions, the fabricated biosensor exhibited wide linear ranges of responses to cholesterol in the concentration ranges of 2.2×10−6 to 5.2×10−4 M, the limit of detection was 0.75 μM (S/N=3). The response time was less than 7 s and the Michaelis–Menten constant ( K m app ) was found as 0.11 mM. In addition, the biosensor also exhibited excellent reproducibility and stability. Along with these attractive features, the biosensor also displayed very high specificity to cholesterol with complete elimination of interference from UA, AA, and glucose.
