Longwei Yin

Shandong University, Chi-nan-shih, Shandong Sheng, China

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Publications (41)178.87 Total impact

  • Xiaoyu Feng · Jianxin Zhang · Longwei Yin ·

    Materials Research Bulletin 11/2015; DOI:10.1016/j.materresbull.2015.11.008 · 2.29 Impact Factor
  • Xiaoyu Feng · Jianxin Zhang · Longwei Yin ·
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    ABSTRACT: LiMn2O4 spinel cathode materials were modified with 1%, 3% and 5% Co3(PO4)2 coating with a simple chemical deposition process, followed by calcinations at 420°C for 3h in air. The Co3(PO4)2 surface modified samples showed much better capacity retention at both room temperature and 60°C than bare LiMn2O4. Especially, 3wt.% Co3(PO4)2 coated sample exhibited superior capacity retention with only 12% capacity loss after 100cycles at 60°C with a final capacity around 110mAhg-1. From the electrochemical impedance spectroscopy (EIS) analysis, Co3(PO4)2 surface coating suppressed the undesirable growth of electrochemical impedance spectroscopy (SEI). The cyclic voltammetry (CV) confirmed that Co3(PO4)2 surface modification improved the stability of the LiMn2O4 structure. Therefore, Co3(PO4)2 will be a promising coating material for LiMn2O4 to improve the cyclic performance.
  • Qun Li · Longwei Yin · Jingyun Ma · Zhaoqiang Li · Zhiwei Zhang · Ailian Chen · Caixia Li ·
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    ABSTRACT: In-situ magnesiothermic reduction reaction route was developed to synthesize mesoporous Si/C (silicon/carbon) hybrids with ordered pore channel retention and tunable carbon incorporated content as high performance anode materials for LIBs (lithium ion batteries). The effect of carbon incorporation on the microstructures and electrochemical performance of the Si/C hybrid LIBs anodes is investigated. The incorporation of carbon in the Si/C hybrids not only prevents the ordered structure of mesoporous silicon from collapsing, but also increases the electrical conductivity of the synthesized Si/C hybrids. The as-prepared Si/C hybrid LIBs anode with an optimal carbon content of 7.05 wt%, displays improved electrochemical performance with a high reversible specific capacity, rate capability and excellent cyclic performance, showing a higher specific capacity of up to 1452 mAh g−1 at a current density of 200 mA g−1 after 100 cycles and a high coulombic efficiency of up to 99.2%. The great improvement of the electrochemical performance of the ordered mesoporous Si/C hybrid LIBs anodes can be attributed to the unique ordered structure, large surface area, the homogeneously incorporated carbon in the Si/C hybrids. The synthesized ordered mesoporous Si/C hybrids are promising for potential applications as LIB anode materials with enhanced electrochemical performance.
    Energy 04/2015; 85. DOI:10.1016/j.energy.2015.03.090 · 4.84 Impact Factor
  • Caixia Li · Longwei Yin ·
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    ABSTRACT: In order to overcome the main obstacles for lithium–sulfur batteries, such as poor conductivity of sulfur, polysulfide intermediate dissolution, and large volume change generated during the cycle process, a hard-template route is developed to synthesize large-surface area carbon with abundant micropores and mesopores to immobilize sulfur species. The microstructures of the C/S hybrids are investigated using field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, nitrogen adsorption–desorption isotherms, and electrochemical impedance spectroscopy techniques. The large surface and porous structure can effectively alleviate large strain due to the lithiation/delithiation process. More importantly, the micropores can effectively confine small molecules of sulfur in the form of S2–4, avoiding loss of active S species and dissolution of high-order lithium polysulfides. The porous C/S hybrids show significantly enhanced electrochemical performance with good cycling stability, high specific capacity, and rate capability. The C/S-39 hybrid with an optimal content of 39 wt% S shows a reversible capacity of 780 mA h g−1 after 100 cycles at the current density of 100 mA g−1. Even at a current density of 5 A g−1, the reversible capacity of C/S-39 can still maintain at 420 mA h g−1 after 60 cycles. This strategy offers a new way for solving long-term reversibility obstacle and designing new cathode electrode architectures.
    Particle and Particle Systems Characterization 03/2015; 32(7). DOI:10.1002/ppsc.201400259 · 3.08 Impact Factor
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    ABSTRACT: A FeCO3/graphene nanocomposite (FCO/GNS), in which FeCO3 nanoflakes aligned by nanowires well dispersed in graphene matrix, is successfully synthesized via a simple one-pot hydrothermal route. With the electronic conductor, buffer, dispersion and synergetic lithium storage effect of graphene, the composite exhibits significantly improved electrochemical activity and cycling stability relative to bare flower-like FeCO3 microspheres, as well as excellent rate performance and a great recovery capability, delivering a charge capacity of 934.4, 798.6, 661.4, 451.9, 403.4, 268.9 and 193.1 mAh g−1 at 0.2, 0.4, 0.8, 2, 3, 4 and 5 C, respectively, and a recovery capacity of up to 1166 mAh g−1 after 255 cycles from 0.1 to 5 C. Combining the experimental data with voltage profiles and CV curves, conversion reactions of the resulted FeCO3 are inferred to be not limited to the transition between FeCO3 and Li2CO3 but involving further reduction of Li2CO3. All the results suggest that the obtained FCO/GNS nanocomposite is a very promising anode material for lithium ion batteries.
    Electrochimica Acta 12/2014; 148:283–290. DOI:10.1016/j.electacta.2014.09.162 · 4.50 Impact Factor
  • Source
    Dong Xiang · Longwei Yin · Jingyun Ma · Enyan Guo · Qun Li · Zhaoqiang Li · Kegao Liu ·
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    ABSTRACT: Nanocomposites of NiFex embedded in ordered mesoporous carbon (OMC) (x = 0, 1, 2) were prepared by a wet impregnation and hydrogen reduction process and were used to construct electrochemical biosensors for the amperometric detection of hydrogen peroxide (H2O2) or glucose. The NiFe2/OMC nanocomposites were demonstrated to have a large surface area, suitable mesoporous channels, many edge-plane-like defective sites, and a good distribution of alloyed nanoparticles. The NiFe2/OMC and Nafion modified glass carbon electrode (GCE) exhibited excellent electrocatalytic activities toward the reduction of H2O2 as well. By utilizing it as a bioplatform, GOx (glucose oxidase) cross-linked with Nafion was immobilized on the surface of the electrode for the construction of an amperometric glucose biosensor. Our results indicated that the amperometric hydrogen peroxide biosensor (NiFe2/OMC + Nafion + GCE) showed good analytical performances in term of a high sensitivity of 4.29 μA mM(-1) cm(-2), wide linearity from 6.2 to 42 710 μM and a low detection limit of 0.24 μM at a signal-to-noise ratio of 3 (S/N = 3). This biosensor exhibited excellent selectivity, high stability and negligible interference for the detection of H2O2. In addition, the immobilized enzyme on NiFe2/OMC + Nafion + GCE, retaining its bioactivity, exhibited a reversible two-proton and two-electron transfer reaction, a fast heterogeneous electron transfer rate and an effective Michaelis-Menten constant (K) (3.18 mM). The GOx + NiFe2/OMC + Nafion + GCE could be used to detect glucose based on the oxidation of glucose catalyzed by GOx and exhibited a wide detection range of 48.6-12 500 μM with a high sensitivity of 6.9 μA mM(-1) cm(-2) and a low detection limit of 2.7 μM (S/N = 3). The enzymic biosensor maintained a high selectivity and stability features, and shows great promise for application in the detection of glucose.
    The Analyst 11/2014; 140(2). DOI:10.1039/c4an01549e · 4.11 Impact Factor
  • Enyan Guo · Longwei Yin ·
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    ABSTRACT: We report on high-performance dye-sensitized solar cells (DSSCs) based on nitrogen doped anatase TiO2–CuxO core–shell mesoporous hybrids synthesized through a facile and controlled combined sol–gel and hydrothermal process in the presence of hexadecylamine as the structure-directing agent. The matching of band edges between CuxO and TiO2 to form a semiconductor heterojunction plays an important role in effective separation of light induced electrons and holes, providing a promising photoanode for DSSCs because of its wide absorption spectrum, high electron injection efficiency, and fast electron transference. DSSCs based on the mesoporous TiO2–CuxO core–shell hybrids show a high short-circuit current density of 9.60 mA cm−2 and a conversion efficiency of 3.86% under one sun illumination. While DSSCs based on the N-doped mesoporous TiO2–CuxO hybrids exhibit the higher short-circuit current density of 13.24 mA cm−2 and a conversion efficiency of 4.57% under one sun illumination. In comparison with un-doped TiO2–CuxO hybrids, the doping of nitrogen into the lattice of TiO2 can extend the light absorption in the ultraviolet range to the visible light region and effectively decrease the recombination rate of photo-generated electrons and holes. The presented N-doped mesoporous TiO2–CuxO hybrids as photoanodes could find potential applications for high performance DSSCs.
    Physical Chemistry Chemical Physics 11/2014; 17(1). DOI:10.1039/C4CP03132F · 4.49 Impact Factor
  • Zhaoqiang Li · Liang Wang · Xiaoli Ge · Hongwei Ge · Longwei Yin ·
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    ABSTRACT: A controllable synthetic route was developed to synthesize nanocrystalline NiO nanoparticles incoporated in ordered mesoporous carbon (OMC), with an adjustable size, content and distribution of NiO nanoparticles, as anode materials for lithium ion batteries (LIBs) with improved electrochemical lithium storage performance. The effects of size, distribution and content of NiO nanoparticles on the electrochemical performances of the mesoporous NiO/OMC nanocomposites as anode materials for LIBs were investigated using galvanostatical charge–discharge and cyclic voltammetry techniques. An optimal 20% NiO content of the one-step route synthesized of 20NiO/OMC nanocomposite with NiO nanoparticles homogeneously embedded within OMC matrices, and with a smaller size of 10 nm of NiO nanoparticles, displays a highly improved rate capability and reversible capacity for LIBs, exhbiting a high specific capacity up to 762 mAh g–1, and a high coulombic efficiency of up to 98.4% after 60 cycles at a current density of 100 mA g–1. Even at a high current of 1600 mA g–1, it still delivers a capacity of 272 mAh g–1, about 5 times the capacity of pure OMC sample. Such significant improvement of electrochemical performance is ascribed to the unique structures of the NiO/OMC nanocomposites with a variety of favorable properties. The OMC matrix with a thin wall provides short solid-state diffusion length of Li, building electron passway between the dielectric NiO nanoparticles, hinder the agglomeration of NiO nanopar- ticles and buffer the volume change of NiO during discharge/charge processes. The addition of appropriate amount of NiO nanoparticles provides a proper surface area to appropriately reduce the number of active sites of OMC and increase the capacity retention. The synergetic effect between the conducting OMC matrix and NiO nanoparticles makes it a promising anode material for LIBs with high specific capacity, high rate capability, high coulombic efficiency.
    Journal of Applied Statistics 10/2014; 6(10). DOI:10.1166/sam.2014.1983 · 0.42 Impact Factor
  • Bin Yao · Zhaojun Ding · Jianxin Zhang · Xiaoyu Feng · Longwei Yin ·
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    ABSTRACT: The severe capacity decay of LiFePO4 at low temperatures (<= 0 degrees C) limits its wide applications as cathode materials for energy storage batteries. Creating comprehensive carbon network between particles with improved electronic conductivity is a well known solution to this problem. Here, a novel structured LiFePO4/C composite was prepared by a facile solid state route, in which nanosized LiFePO4 spheres were encapsulated by in-situ graphitized carbon cages. With the enhancement in electronic conductivity (2.15e-1 S cm(-l)), the composite presented excellent rate performance at room temperature and remarkable capacity retention at -40 degrees C, with charge transfer resistance much lower than commercial LiFePO4.
    ChemInform 08/2014; 45(33). DOI:10.1002/chin.201433016
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    ABSTRACT: To improve the electrochemical performance of spinel ZnMn2O4, i.e., its limited specific capacity, cycling performance, and rate properties, owing to its inherent poor electrical conductivity and large volume changes during lithiation and delithiation processes, spinel ZnMn2O4 nanocrystals are anchored into a three dimensional (3D) porous carbon aerogel (CA) through a facile solution immersion chemical route. The designed 3D spinel ZnMn2O4/CA hybrids display the advantages of both spinel ZnMn2O4 and porous CA: enormous interfacial surface area, connected 3D framework, abundant porosity and high electron transport properties of CA, and electrochemical properties of nanostructured spinel ZnMn2O4 oxide materials. The synthesized novel ZnMn2O4/CA hybrids display a significantly improved electrochemical performance, with a high reversible specific capacity, and high-rate capability, as well as an excellent cycling performance, superior to that of previously reported ZnMn2O4-based materials. After 50 cycles, the 50%ZnMn2O4/CA hybrid displays a reversible capacity of 833 mAh g−1 at a current density of 100 mAg-1, much higher than the theoretical capacity of 784 mAh g−1 for pure spinel ZnMn2O4 materials, corresponding to a Coulombic efficiency of 99.9%. The greatly improved cycle stability, specific capacity, and high rate performance of the ZnMn2O4/CA hybrids can be attributed to the synergistic interaction between spinel-structured ZnMn2O4 nanoparticles and the 3D interconnected porous CA matrix.
    Advanced Functional Materials 07/2014; 24(26). DOI:10.1002/adfm.201400108 · 11.81 Impact Factor
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    ABSTRACT: To eliminate capacity-fading effects due to the loss of sulfur cathode materials as a result of polysulfide dissolution in lithium–sulfur (Li–S) cells, 3D carbon aerogel (CA) materials with abundant narrow micropores can be utilized as an immobilizer host for sulfur impregnation. The effects of S incorporation on microstructure, surface area, pore size distribution, and pore volume of the S/CA hybrids are studied. The electrochemical performance of the S/CA hybrids is investigated using electrochemical impedance spectroscopy, galvanostatical charge–discharge, and cyclic voltammetry techniques. The 3D porous S/CA hybrids exhibit significantly improved reversible capacity, high-rate capability, and excellent cycling performance as a cathode electrode for Li–S batteries. The S/CA hybrid with an optimal incorporating content of 27% S shows an excellent reversible capacity of 820 mAhg−1 after 50 cycles at a current density of 100 mAg−1. Even at a current density of 3.2C (5280 mAg−1), the reversible capacity of 27%S/CA hybrid can still maintain at 521 mAhg−1 after 50 cycles. This strategy for the S/CA hybrids as cathode materials to utilize the abundant micropores for sulfur immobilizers for sulfur impregnation for Li–S battery offers a new way to solve the long-term reversibility obstacle and provides guidelines for designing cathode electrode architectures.
    Advanced Functional Materials 05/2014; 24(17). DOI:10.1002/adfm.201303080 · 11.81 Impact Factor
  • Enyan Guo · Longwei Yin · Luyuan Zhang ·
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    ABSTRACT: We report on solar cells based on CdS QD sensitized anatase TiO2 hierarchical nanostructures prepared via a facile and controlled hydrothermal process. To adjust the size of CdS QDs, the TiO2 surfaces were first treated with thiolactic acid which provides a binding site for Cd2+ ions. CdS QDs with controllable size are grown onto the TiO2 hierarchical nanostructures. The CdS QDs/TiO2 hierarchical heterojunction nanocomposites display a red shift from the ultraviolet to the visible light region with a longer wavelength for the absorption edge. The matching of band edges between CdS and TiO2 to form a semiconductor heterojunction plays an important role in effective separation of light induced electrons and holes, providing a promising photoanode for its wide absorption spectrum, high electron injection efficiency, and fast electron transference. Under UV-vis irradiation, both CdS and TiO2 are excited. Under visible light irradiation, photons are captured by CdS QDs, with the photogenerated electron-hole pairs rapidly separated into electrons and holes at the interface between TiO2 and CdS QDs. In addition to this, more photoelectrons are generated from TiO2 by harvesting UV photons. TiO2 collects the photoelectrons from CdS and passes them through to the back contact. The holes (from both CdS and TiO2) generated in the process are transferred to the solid-liquid interface. Under one sun illumination, the solar cells based on CdS QDs/TiO2 hierarchical heterojunction nanocomposites with a smaller average size of 7.6 nm for CdS QDs show a maximum short circuit current density of 6.09 mA cm−2 and a conversion efficiency of 3.06%. The performance improvement of the solar cells based on CdS QDs/TiO2 hierarchical nanostructures can be attributed to the unique microstructure characteristics and the bandgap energy matching between the CdS QDs and TiO2.
    CrystEngComm 04/2014; 16(16):3403. DOI:10.1039/c4ce00019f · 4.03 Impact Factor
  • Xiaoyu Feng · Yun Tian · Jianxin Zhang · Longwei Yin ·
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    ABSTRACT: In this paper, the effect of different aluminum precursors, i.e., Al(OH)3 and Al2O3, on the structural and electrochemical properties of spinel LiMn2 − xAlxO4 (x = 0, 0.05, 0.1, 0.15) is investigated by X-ray diffraction (XRD), micro-Raman spectroscopy (RS), field-emission scanning electron microscopy (FE-SEM) and charge–discharge cycling test. In particular, the ratio of Raman intensity at 625 cm− 1 to Raman intensity at 585 cm− 1 provides crucial insights into the Al substitution in spinel LiMn2O4 lattice. The XRD patterns and FE-SEM images show that the crystal structure and the particle morphologies of LiMn2 − xAlxO4 are not altered by use of either Al(OH)3 or Al2O3 as Al precursors. However, the Raman spectra show that Al doping behavior is significantly affected by Al precursors, with Al(OH)3 serving as a more effective Al precursor than Al2O3. Such conclusion is further supported by the electrochemical cycling results.
    Powder Technology 02/2014; 253:35–40. DOI:10.1016/j.powtec.2013.11.006 · 2.35 Impact Factor
  • Zhaoqiang Li · Xuekun Wang · Changbin Wang · Longwei Yin ·
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    ABSTRACT: A hybrid of iron oxide nanoparticle modified ordered mesoporous carbon (OMC) was successfully prepared via a controllable two-step route. Electrochemical lithium storage experimental results reveal that the FeOx/OMC composites can effectively reduce the capacity decay caused by volume change, and decrease the irreversible capacity of ordered mesoporous carbon. The first discharge capacities of FeOx/OMC and OMC are 1718 mA h g−1 and 1685 mA h g−1, respectively, while the first charge capacities of the FeOx/OMC and OMC electrodes are 1004 mA h g−1 and 528 mA h g−1, respectively. Apparently, the FeOx/OMC hybrids display a higher reversible capacity of more than 660 mA h g−1 and higher initial coulombic efficiency (58.4%). More importantly, at high charge-discharge rates, even at a current density of 1600 mA g−1, the capacity of the FeOx/OMC electrode is still maintained at 320 mA h g−1 even after 50 cycles, almost 5.4 times higher than the capacity of 50 mA h g−1 for the pure OMC sample. The high rate of performance is important for applications where fast charge and discharge are needed. The prominent improvement of electrochemical performance can be attributed to the synergistic effects of the FeOx/OMC composites. The FeOx nanoparticles can reduce the large amounts of active sites due to the high specific surface of the OMC, which results in a high irreversible capacity. While the OMC in the composite not only provides an elastic buffer space to accommodate the volume expansion/contraction of FeOx nanoparticles during the Li ions insertion/extraction process, but also efficiently prevents crumbling of electrode material upon continuous cycling, thus maintaining large capacity, good Coulombic efficiency, high rate capability and cycling stability. Furthermore, the OMC in the composite with good electrical conductivity can serve as the conductive channels between FeOx nanoparticles. This excellent electrochemical performance of the FeOx/OMC hybrid makes it a candidate anode material for commercial lithium-ion batteries.
    RSC Advances 10/2013; 3(38):17097. DOI:10.1039/c3ra40682b · 3.84 Impact Factor
  • Xuekun Wang · Zhaoqiang Li · Longwei Yin ·
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    ABSTRACT: We developed a facile infiltration chemical route to fabricate nanocomposites with SnO2 nanoparticle embedded ordered mesoporous carbon (SnO2@OMC) as anode materials for lithium-ion batteries application. The content of SnO2 in the composites can be optimized by changing the mass ratio of SnCl2·2H2O to OMC. The as-prepared materials were characterized by X-ray diffraction, N2 adsorption-desorption analysis techniques, field emission scanning electron microscopy, and high resolution transmission electron microscopy. Electrochemical performance results reveal that the SnO2@OMC composite containing 20 at% SnO2 displays an extraordinary reversible capacity up to 769 mA h g−1 and a high coulombic efficiency up to nearly 98.7% even after 60 cycles at a high current density of 100 mA g−1. Meanwhile, SnO2@OMC composite exhibits excellent rate capabilities. Even at a current rate as high as 1600 mA g−1, it still maintains a stable charge-discharge capacity of 440 mA h g−1 after 60 cycles. The outstanding electrochemical performance of the synthesized SnO2@OMC composites could be ascribed to its unique structural characteristics. The SnO2@OMC nanocomposites are promising candidates as anode materials for rechargeable lithium-ion batteries.
    CrystEngComm 10/2013; 15(37):7589. DOI:10.1039/c3ce41256c · 4.03 Impact Factor
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    Yubing Xia · Longwei Yin ·
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    ABSTRACT: The core-shell structured Fe2O3@TiO2 nanocomposites prepared via a heteroepitaxial growth route using the Fe2O3 spindle as a hard template display improved photocatalytic degradation activity for Rhodamine B dye under visible light irradiation. The ratio of α-Fe2O3 : TiO2 in the α-Fe2O3@TiO2 core-shell nanocomposites can be tuned by etching the α-Fe2O3 core via controlling the concentration of HCl and etching time. An appropriate concentration of the Fe2O3 core could effectively induce a transition of the optical response from the UV to the visible region and decrease the recombination rate of photogenerated electrons and the holes of the core-shell structured catalyst, greatly contributing to the enhancement of visible light response and visible light photocatalytic activity of the Fe2O3@TiO2 catalysts. It is revealed that the optical response and photocatalytic performance of the core-shell α-Fe2O3@TiO2 nanocomposites can be tuned by adjusting the molar ratio of Fe2O3 : TiO2 of the α-Fe2O3@TiO2 nanocomposites. The α-Fe2O3@TiO2 core-shell nanocomposite with an optimal molar ratio of 7% for Fe2O3 : TiO2 exhibits the best photocatalytic performance under visible light irradiation. It is shown that the Fe2O3/TiO2 heterojunction structure is responsible for the efficient visible-light photocatalytic activity. As the concentration of Fe2O3 is high, Fe(3+) ions will act as recombination centres of the photogenerated electrons and holes. The present core-shell Fe2O3@TiO2 nanoparticles displaying enhanced photodegradation activity could find potential applications as photocatalysts for the abatement of various organic pollutants.
    Physical Chemistry Chemical Physics 10/2013; 15(42). DOI:10.1039/c3cp53178c · 4.49 Impact Factor
  • Jingyun Ma · Dong Xiang · Zhaoqiang Li · Qun Li · Xuekun Wang · Longwei Yin ·
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    ABSTRACT: The ordered mesoporous carbon/TiO2 (OMCT) nanocomposites with TiO2 nanocrystals embedded within ordered mesoporous carbon (OMC) were prepared by a simple solvothermal method. The effect of TiO2 nanoparticle incorporation in OMC matrix on the mesoporous structure, pore size, pore volume, surface area and microstructure of OMCT composites was investigated using X-ray diffraction, N2 adsorption-desorption and Brunauer-Emmett-Teller method, scanning electron microscopy and transmission electron microscopy. The electrochemical lithium storage capacities of OMCT composites with different incorporated TiO2 nanoparticles are comparatively investigated using cyclic voltammetry and galvanostatic charge-discharge techniques. It is suggested that the OMCT composites as anode materials for lithium ion batteries display a greatly improved electrochemical performance with high reversible capacity, coulombic efficiency, rate capability and cycling performance. As an anode electrode for Li-ion battery, OMCT15 composite with an incorporated TiO2 nanocrystal content possesses a high reversible capacity of 540.9 mA h g−1 even up to 60 cycles at a high current density of 100 mA g−1, with a stable coulombic efficiency of 98% and good rate capability. Especially at the current density of 1600 mA g−1 after 50 cycles, the reversible capacity of the OMCT15 remains at a value of 260 mA h g−1, 5 times that of the OMC (48.9 mA h g−1) and 21 times that of the pure TiO2 (12.4 mA h g−1) electrodes, respectively. The improved electrochemical lithium storage performance of high reversible capacity, coulombic efficiency, rate performance and cycling ability can be mainly attributed to the synergic effects between the TiO2 nanoparticles and the three dimensional OMC matrices.
    CrystEngComm 09/2013; 15(34):6800. DOI:10.1039/c3ce40642c · 4.03 Impact Factor
  • Ailian Chen · Caixia Li · Rui Tang · Longwei Yin · Yongxin Qi ·
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    ABSTRACT: A novel hybrid of MoO2-ordered mesoporous carbon (MoO2-OMC) was prepared through a two-step solvothermal chemical reaction route. The electrochemical performances of the mesoporous MoO2-OMC hybrids were examined using galvanostatical charge-discharge, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS) techniques. The MoO2-OMC hybrid exhibits significantly improved electrochemical performance of high reversible capacity, high-rate capability, and excellent cycling performance as an anode electrode material for Li ion batteries. It is revealed that the MoO2-OMC hybrid could deliver the first discharge capacity of 1641.8 mA h g(-1) with an initial Coulombic efficiency of 63.6%, and a reversible capacity as high as 1049.1 mA h g(-1) even after 50 cycles at a current density of 100 mA g(-1), much higher than the theoretical capacity of MoO2 (838 mA h g(-1)) and OMC materials. The MoO2-OMC hybrid demonstrates an excellent high rate capability with capacity of ∼600 mA h g(-1) even at a charge current density of 1600 mA g(-1) after 50 cycles, which is approximately 11.1 times higher than that of the OMC (54 mA h g(-1)) materials. The improved rate capability and reversible capacity of the MoO2-OMC hybrid are attributed to a synergistic reaction between the MoO2 nanoparticles and mesoporous OMC matrices. It is noted that the electrochemical performance of the MoO2-OMC hybrid is evidently much better than the previous MoO2-based hybrids.
    Physical Chemistry Chemical Physics 07/2013; 15(32). DOI:10.1039/c3cp51255j · 4.49 Impact Factor
  • Dong Xiang · Rui Tang · Qingcai Su · Longwei Yin ·
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    ABSTRACT: Hybrids of bimetallic NiFex crystalline nanoparticles homogeneously embedded in ordered mesoporous carbon (OMC) for electrochemical hydrogen storage applications were fabricated through wet impregnation and H2 reduction techniques. The size and distribution of NiFex nanoparticles of NiFex/OMC hybrids can be tuned by controlling the molar ratio of Ni:Fe, with the smallest diameter of 4.7 nm for the NiFe2 alloy nanoparticles. The effects of NiFex nanoparticle incorporation into the OMC matrix on the surface area, pore volume, pore size and electrochemical hydrogen storage performances were comparatively investigated using adsorption isotherms of nitrogen, electrochemical impedance spectroscopy, potentiodynamic polarization, cyclic voltammetry and galvanostatic charge–discharge techniques. With the molar ratio of Ni:Fe decreasing, the discharge capacity and the cycle performance of the NiFex/OMC hybrids display a notable improvement due to the homogenous dispersion of NiFex nanoparticles, higher surface area, larger mesopore volume, lower defect ration, and smaller charge-transfer resistance. The NiFe2/OMC samples display greatly improved electrochemical hydrogen storage discharge capacity of 418 mA h g−1, which is about four times as high as that of the pure OMC electrode.
    CrystEngComm 06/2013; 15(27):5442-5451. DOI:10.1039/C3CE40369F · 4.03 Impact Factor
  • Jianmin Wu · Longwei Yin · Luyuan Zhang ·
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    ABSTRACT: The modification of electronic structure, bandgap energy and photoluminescence properties of hexagonal boron nitride (h-BN) nanosheets has been challenging due to the inherent inertness and chemical stability of h-BN. In the present work, we realized tuning the electronic structure and bandgap energy properties of h-BN nanosheets via a controllable Ce3+ ions doping through a one-step facile thermal chemical reaction route using HBO3, C3H6N6 and Ce(Ac)3·nH2O as reactant precursors. As the Ce3+ ions incorporating content is lower than the critical threshold saturation value of 1.25%, the Ce-doped BN samples show an obvious band gap monotonically narrowing trend from 4.42 eV of pure BN to 3.31 eV for 1.25% Ce-doped BN nanosheets. With incorporation of Ce3+ ions into the lattice of h-BN, the intensity of electron paramagnetic resonance (EPR) signals closely associated with the nitrogen vacancies in Ce-doped BN samples, displays a decline trend with increasing the concentration of the incorporated Ce3+ ions, suggesting a decrease in the concentration of paramagnetic centers. The introduction of Ce3+ ions can result in the formation of a doping energy level between the conduction and valence bands of BN, and thus shifts the absorption band to the large-wavelength region, corresponding to the bandgap energy narrowing of Ce-doped BN, resulting in a red shift of the absorption edge of the Ce-doped BN samples. The B–N–O–Ce bonding due to the Ce3+ ion doping is responsible for bandgap energy narrowing in the Ce-doped BN materials. As the concentration of the incorporated Ce3+ ions reaches the critical threshold value of 1.25%, no more nitrogen vacancies are available, so the bandgap energy narrowing effect from the Ce3+ ion doping is reduced.
    RSC Advances 04/2013; 3(20):7408-7418. DOI:10.1039/C3RA23132A · 3.84 Impact Factor