Sheng Dai

Oak Ridge National Laboratory, Oak Ridge, Florida, United States

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Publications (654)3214.03 Total impact

  • Advanced Materials 08/2015; · 17.49 Impact Factor
  • Nature Communications 08/2015; · 10.74 Impact Factor
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    Pengfei Zhang · Huiyuan Zhu · Sheng Dai
    ChemCatChem 08/2015; DOI:10.1002/cctc.201500368 · 5.04 Impact Factor
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    ABSTRACT: Rare-earth elements provide the cornerstones to clean sustainable energy and modern technologies such as computers, communications, and transportation. As such, the recovery of rare earths (REs) from minerals such as bastnaesite remains important for modern times. As the light lanthanides (La–Nd) constitute the majority (typically >98.7 %) of the REs in bastnaesite with the heavy REs (Sm–Lu) contributing the remainder (approximately 1.3 %), an enrichment of heavier REs may serve as an effective means of assisting rare-earth recovery. Such an extractive metallurgy process involving ionic liquids (ILs) leads to an enrichment of heavy REs by nearly an order of magnitude. The acidic IL N,N-dimethylacetamidium bis(trifluoromethylsulfonyl)imide (DMAH+NTf2–) in the IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM+NTf2–) dissolves froth flotation bastnaesite, synthetic bastnaesite analogues (RECO3F), RE2O3, and RE2(CO3)3 minerals. An overall reaction for the dissolution of bastnaesite is proposed for this IL system. This IL system may provide the initial stages of a greater RE separation scheme for bastnaesite froth flotation concentrates.
    Berichte der deutschen chemischen Gesellschaft 08/2015; DOI:10.1002/ejic.201500509
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    ABSTRACT: We have studied the origin of the exchange bias effect in the Au-Fe3O4 dumbbell nanoparticles in two samples with different sizes of the Au seed nanoparticles (4.1 and 2.7 nm) and same size of Fe3O4 nanoparticles (9.8 nm). The magnetization, small-angle neutron-scattering, synchrotron x-ray diffraction, and scanning transmission electron microscope measurements determined the antiferromagnetic FeO wüstite phase within Fe3O4 nanoparticles, originating at the interface with the Au nanoparticles. The interface between antiferromagnetic FeO and ferrimagnetic Fe3O4 is giving rise to the exchange bias effect. The strength of the exchange bias fields depends on the interfacial area and lattice mismatch between both phases. We propose that the charge transfer from the Au nanoparticles is responsible for a partial reduction of the Fe3O4 into the FeO phase at the interface with Au nanoparticles. The Au-O bonds are formed, presumably across the interface to accommodate an excess of oxygen released during the reduction of magnetite.
    Physical review. B, Condensed matter 08/2015; 92(5):054416. DOI:10.1103/PhysRevB.92.054416 · 3.66 Impact Factor
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    ABSTRACT: Polymeric amines such as poly(ethyleneimine) supported on mesoporous oxides are promising candidate adsorbents for CO2 capture processes. An important aspect to the design and optimization of these materials is a fundamental understanding of how the properties of the oxide support such as pore structure, particle morphology, and surface properties affect the efficiency of the guest polymer in its interactions with CO2. Here, these issues are directly addressed via the preparation of an array of SBA-15 support materials with varying textural and morphological properties and with varying content of zirconium doped into the material. Zirconium is incorporated into the SBA-15 either during the synthesis of the SBA-15, or post-synthetically via deposition of Zr species on pre-synthesized SBA-15. It is found that the method of Zr incorporation altered the textural and morphological properties of the parent SBA-15 in different ways. Importantly, the CO2 capacity of SBA-15 impregnated with PEI increased with doped Zr for a 'standard' SBA-15 containing significant microporosity, while no increase in the CO2 capacity was observed upon Zr incorporation for an SBA-15 with improved textural properties. The collected data demonstrate that the textural and morphological properties of the support play a more significant role in impact the ability of PEI to capture CO2 than the support composition.
    Langmuir 08/2015; DOI:10.1021/acs.langmuir.5b02114 · 4.46 Impact Factor
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    ABSTRACT: In this communication, we report a facile approach to constructing catalytic active hierarchical interfaces in 1-dimensional (1D) nanostructure, exemplified by the synthesis of TiO2-supported PtFe-FeOx nanowires (NWs). The hierarchical interface, constituting of atomic level interactions between PtFe and FeOx within each NW and the interactions between NWs and support (TiO2), enables CO oxidation with 100% conversion at room temperature. We identify the role of the two interfaces by probing the CO oxidation reaction with isotopic labeling experiments. Both the oxygen atoms (Os) in FeOx and TiO2 participate in the initial CO oxidation, facilitating the reaction through a redox pathway. Moreover, the intact 1D structure leads to the high stability of the catalyst. After 30 h in the reaction stream, the PtFe-FeOx/TiO2 catalyst exhibits no activity decay. Our results provide a general approach and new insights into the construction of hierarchical interfaces for advanced catalysis.
    Journal of the American Chemical Society 08/2015; DOI:10.1021/jacs.5b07011 · 11.44 Impact Factor
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    ABSTRACT: Graphene and graphene/metal oxide composite materials have attracted considerable interest for energy materials due to their excellent electrochemical performances. Here we propose using melamine as a template for the synthesis of cambered nano-walls of SnO2/rGO materials. Melamine powder can effectively absorb SnO2/GO from the solution to form a core-shell structure of melamine@SnO2/GO. After thermal reduction of GO at 200 oC to form the melamine@SnO2/rGO, melamine was dissolved in hot water at 80 oC, leaving behind the cambered SnO2/rGO nano-walls. Melamine is recyclable since it precipitates when its solution cools to room temperature. The thickness of the SnO2/rGO nano-walls can be easily controlled by adjusting the mass ratio of melamine to SnO2/GO. When the mass ratio was set to ten, cambered walls of SnO2/rGO with thickness of about 100-200 nm were achieved. The resulting SnO2/rGO delivered an initial reversible capacity of at 998 mAh/g at a current density of 100 mA/g and a capacity of 855 mAh/g after 100 discharge-charge cycles in a potential range between 0.02 and 3.0 V vs. Li/Li+. It also showed good rate performance with a reversible capacity of 460 mAh/g at 1A/g. These high capacities can be linked to the special cambered nano-walls which ensure fast solid diffusion in addition to providing an effective liquid-channel and buffer-volume in the electrode. The proposed synthesis method is easily scalable and should be applicable to many other graphene based energy materials.
    07/2015; DOI:10.1039/C5TA03166D
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    ABSTRACT: Herein, we report a green, fast, efficient mechanochemical strategy for charged porous polymers (CPPs). A cationic CPP with basic anions and an anionic CPP with Li(+) cations were fabricated by solid grinding under solvent-free conditions. Compared with solution-based synthesis, mechanochemical grinding can shorten the reaction time from dozens of hours to several minutes (60-90 min) to form polymers possessing a high molecular mass and low polydispersity. During the construction of CPPs, a Pd-catalyzed solid polycondensation based on unactivated organic linkers was introduced. In particular, CPPs with basic phenolic or proline anions showed good activity and stability in SO2 capture, and Li(+) -functionalized CPPs can be post-modified to CPPs with other metal ions by ion exchange, highlighting the tailorable feature of ionic-modified CPPs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Chemistry - A European Journal 07/2015; 21(37). DOI:10.1002/chem.201501814 · 5.70 Impact Factor
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    ABSTRACT: Na-ion batteries are becoming comparable to Li-ion batteries because of their similar chemical characteristics and abundant sources of sodium. However, the materials production should be cost-effective in order to meet the demand for large-scale application. Here, a series of nanosized high-performance cathode materials, Na3 (VO1-x PO4 )2 F1+2x (0≤x≤1), has been synthesized by a solvothermal low-temperature (60-120 °C) strategy without the use of organic ligands or surfactants. The as-synthesized Na3 (VOPO4 )2 F nanoparticles show the best Na-storage performance reported so far in terms of both high rate capability (up to 10 C rate) and long cycle stability over 1200 cycles. To the best of our knowledge, the current developed synthetic strategy for Na3 (VO1-x PO4 )2 F1+2x is by far one of the least expensive and energy-consuming methods, much superior to the conventional high-temperature solid-state method. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Angewandte Chemie International Edition 07/2015; DOI:10.1002/anie.201503188 · 11.26 Impact Factor
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    ABSTRACT: Unique synergistic effects between phosphonium-alkylphosphate ionic liquids (ILs) and zinc dialkyldithiophosphate (ZDDP) are discovered when used together as lubricant additives, resulting in significant friction and wear reductions along with distinct tribofilm composition and mechanical properties. The synergism is attributed to the remarkably 30-70× higher-than-nominal concentrations of hypothetical new compounds (via anion exchange between IL and ZDDP) on the fluid surface/interface. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Advanced Materials 07/2015; DOI:10.1002/adma.201502037 · 17.49 Impact Factor
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    ABSTRACT: A new kind of ionic liquid based on complexation of dipropyl sulfide (DPS) and AlCl3 has been prepared. The equivalent concentration of AlCl3 in the ionic liquid is as high as 2.3 M. More importantly, it is highly fluidic and exhibits an ambient ionic conductivity of 1.25 x 10-4 S cm-1. This new ionic liquid can be successfully used as an electrolyte for electrodeposition of aluminum.
    Chemical Communications 07/2015; DOI:10.1039/C5CC05233E · 6.83 Impact Factor
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    ABSTRACT: Spinel LiMn1.5Ni0.5O4 (LMNO) cathode material synthesized by a sol-gel method is modified by MgF2 nano-coating via wet coating strategy. The results of X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) showed that the MgF2 nano-coating layers do not physically change the bulk structure of pristine material. Compared with the pristine compound, the MgF2-coated LMNO electrodes display enhanced cycling stabilities. Particularly, the 5 wt.% MgF2-coated LMNO demonstrates the best reversibility, with capacity retention of 89.2% after 100 cycles, much higher than that of the pristine material, 70.0%. The dQ/dV analysis and apparent Li+ diffusion coefficient calculation prove that the kinetic property is enhanced after MgF2 surface modification, which partly explains the improved electrochemical performances. Electrochemical impedance spectroscopy (EIS) and flourier transform infrared spectroscopy (FTIR) data confirm that MgF2 coating layer helps in suppressing the fast growth of solid electrolyte interface (SEI) film in repeated cycling, which effectively stabilizes the spinel structure. Additionally, differential scanning calorimetry (DSC) tests show that the MgF2 nano-coating layer also helps in enhancing the thermal stability of LMNO cathode.
    Nanoscale 07/2015; DOI:10.1039/C5NR03564C · 7.39 Impact Factor
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    ABSTRACT: The hydrogenation of levulinic acid has been studied using Ru supported on ordered mesoporous carbons (OMCs) prepared by soft-templating. P- and S-containing acid groups were introduced by postsynthetic functionalization before the addition of 1 % Ru by incipient wetness impregnation. These functionalities and the reaction conditions mediate the activity and selectivity of the levulinic acid hydrogenation. The presence of S-containing groups (Ru/OMC-S and Ru/OMC-P/S) deactivates the Ru catalysts strongly, whereas the presence of P-containing groups (Ru/OMC-P) enhances the activity compared to that of pristine Ru/OMC. Under mild conditions (70 °C and 7 bar H2 ) the catalyst shows high selectivity to γ-valerolactone (GVL; >95 %) and high stability on recycling. However, under more severe conditions (200 °C and p H 2=40 bar) Ru/OMC-P is particularly able to promote GVL ring-opening and the consecutive hydrogenation to pentanoic acid. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    ChemSusChem 06/2015; DOI:10.1002/cssc.201500331 · 7.66 Impact Factor
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    ABSTRACT: The viability of seawater-based uranium recovery depends on the uranium adsorption rate and capacity, since the concentration of uranium in the oceans is relatively low (3.3 μgL−1). An important consideration for a fast adsorption is to maximize the adsorption properties of adsorbents such as surface areas and pore structures, which can greatly improve the kinetics of uranium extraction and the adsorption capacity simultaneously. Following this consideration, macroporous monolith adsorbents were prepared from the copolymerization of acrylonitrile (AN) and N,N’-methylenebis(acrylamide) (MBAAm) based on a cryogel method using both hydrophobic and hydrophilic monomers. The monolithic sorbents were tested with simulated seawater containing a high uranyl concentration (~6 ppm) and the uranium adsorption results showed that the adsorption capacities are strongly influenced by the ratio of monomer to the crosslinker, i.e., the density of the amidoxime groups. The preliminary seawater testing indicates the high salinity content of seawater does not hinder the adsorption of uranium.
    RSC Advances 05/2015; 5(62). DOI:10.1039/C5RA02131F · 3.84 Impact Factor
  • Ziqi Tian · Sheng Dai · De-En Jiang
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    ABSTRACT: Porphyrin-based two-dimensional polymers have uniform micropores and close to atom-thin thicknesses, but they have not been explored for gas separation. Herein we design various expanded porphyrin derivatives for their potential application in membrane gas separation, using CO2/N2 as an example. Pore sizes are determined based on both van der Walls radius and electron density distribution. Potential energy curves for CO2 and N2 passing are mapped by dispersion-corrected density functional theory calculations. The passing-through barriers are used to evaluate CO2/N2 separation selectivity. Promising subunits for CO2 separation have been selected from the selectivity estimates. 2D membranes composed of amethyrin derivatives are shown to have high ideal selectivity on the order of 106 for CO2/N2 separation. Classical molecular dynamics simulation yields a permeance of 104 - 105 GPU for CO2 through extended 2D membranes based on amethyrin derivatives. This work demonstrates that porphyrin systems could offer an attractive bottom-up approach for 2D porous membranes.
    ACS Applied Materials & Interfaces 05/2015; 7(23). DOI:10.1021/acsami.5b03275 · 6.72 Impact Factor
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    ABSTRACT: A facile template-free strategy for the synthesis of mesoporous phenolic polymers with attractive porosities, nitrogen-containing functionalities, and intrinsic hydrophilic skeletons is presented. The resultant polymer has a high BET surface area (548 m2 g-1) and mesopore size (13 nm) and exhibits superior glycopeptide-capturing performance, thus, revealing the potential application of mesoporous polymers in highly selective glycopeptide enrichment. This general capture protocol may open up new opportunities for the development of glycoproteomes.
    ACS Macro Letters 05/2015; 4(5):570-574. DOI:10.1021/acsmacrolett.5b00235 · 5.24 Impact Factor
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    ABSTRACT: Ultrahigh surface area carbons (USACs, e.g., >2000 m2/g) are attracting tremendous attention due to their outstanding performance in energy-related applications. The state-of-art approaches to USACs involve templating or activation methods and all these techniques show certain drawbacks. In this work, a series of USACs with specific surface areas up to 3633 m2/g were prepared in two steps: hydrothermal carbonization (200 °C) of carbonated beverages (CBs) and further thermal treatment in nitrogen (600–1000 °C). The rich inner porosity is formed by a self-templated process during which acids and polyelectrolyte sodium salts in the beverage formulas make some contribution. This strategy covers various CBs such as Coca Cola®, Pepsi Cola®, Dr. Pepper®, and Fanta® and it enables an acceptable product yield (based on sugars), for example: 21 wt% for carbon (2940 m2/g) from Coca Cola®. Being potential electrode materials for supercapacitors, those carbon materials possessed a good specific capacitance (57.2–185.7 F g−1) even at a scan rate of 1000 mV s−1. Thus, a simple and efficient strategy to USACs has been presented.
    Carbon 05/2015; 93. DOI:10.1016/j.carbon.2015.05.019 · 6.16 Impact Factor
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    ABSTRACT: Higher alcohol synthesis from syngas is studied over K/MoS2 domains supported on mesoporous carbon (C), mixed MgAl oxide (MMO), or mixtures thereof. While the carbon support offers high ethanol productivity, the MMO support yields enhanced C3+OH selectivity. MoKMMO-C, whereby Mo is initially contained on MMO then ground with carbon, behaves similar to the parent MoKMMO catalyst, as Mo on MMO has limited mobility during reaction. In contrast, on MoKC-MMO, significant Mo migrates from C to MMO during reaction, giving reactivity associated with Mo species on both supports (high C3+OH selectivity and productivity). MoS2 domain structures are correlated with the selectivity of the catalysts (C3+OH selectivity ∼ double MoS2 layers, total hydrocarbon selectivity ∼ single MoS2 layers). This study advances the understanding of the support’s effect on structure–reactivity relationships for this family of catalysts and introduces a new catalyst composition with desirable reactivity.
    Journal of Catalysis 04/2015; 324. DOI:10.1016/j.jcat.2015.01.015 · 6.07 Impact Factor
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    ABSTRACT: A new fluorinated and alkylated lithium malonatoborate salt, lithium bis(2-methyl-2-fluoromalonato)borate (LiBMFMB), has been synthesized for lithium ion battery application. The new salt based electrolyte, 0.8 M LiBMFMB in ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (1:2 by wt.), exhibits good cycling stability and rate capability in LiNi0.5Mn1.5O4 and graphite based half-cells.
    Chemical Communications 04/2015; 51(48). DOI:10.1039/C5CC01428J · 6.83 Impact Factor

Publication Stats

16k Citations
3,214.03 Total Impact Points

Institutions

  • 1991–2015
    • Oak Ridge National Laboratory
      • Chemical Sciences Division
      Oak Ridge, Florida, United States
  • 1988–2015
    • The University of Tennessee Medical Center at Knoxville
      Knoxville, Tennessee, United States
  • 2014
    • Vanderbilt University
      • Department of Chemical and Biomolecular Engineering
      Nashville, Michigan, United States
    • Zhejiang University
      • Department of Chemical and Biochemical Engineering
      Hang-hsien, Zhejiang Sheng, China
  • 2012
    • Brookhaven National Laboratory
      New York, New York, United States
  • 2011–2012
    • Fudan University
      • Department of Chemistry
      Shanghai, Shanghai Shi, China
  • 2009–2011
    • New Mexico State University
      • Department of Chemistry and Biochemistry
      Las Cruces, New Mexico, United States
    • Brown University
      • Department of Chemistry
      Providence, Rhode Island, United States
  • 2008
    • Jilin University
      • State Key Laboratory of Inorganic Synthesis and Preparative
      Yung-chi, Jilin Sheng, China
    • Georgia Institute of Technology
      • School of Civil & Environmental Engineering
      Atlanta, Georgia, United States
  • 2001
    • The Scripps Research Institute
      • Department of Cell and Molecular Biology
      La Jolla, California, United States
    • Nankai University
      • College of Environmental Science and Engineering
      Tianjin, Tianjin Shi, China
    • Donald Danforth Plant Science Center
      San Luis, Missouri, United States
  • 1989–1997
    • University of Tennessee
      • Department of Chemistry
      Knoxville, Tennessee, United States