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One-pot solvothermal synthesis of graphene wrapped rice-like ferrous carbonate nanoparticles as anode materials for high energy lithium-ion batteries.
Nanoscale
PUBLISHED: 11-20-2014
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Well dispersed rice-like FeCO3 nanoparticles were produced and combined with reduced graphene oxide (RGO) via a one-pot solvothermal route. SEM characterization shows that rice-like FeCO3 nanoparticles are homogeneously anchored on the surface of the graphene nanosheets; the addition of RGO is helpful to form a uniform morphology and reduce the particle size of FeCO3 to nano-grade. As anode materials for lithium-ion batteries, the FeCO3/RGO nanocomposites exhibit significantly improved lithium storage properties with a large reversible capacity of 1345 mA h g(-1) for the first cycle and a capacity retention of 1224 mA h g(-1) after 50 cycles with a good rate capability compared with pure FeCO3 particles. The superior electrochemical performance of the FeCO3/RGO nanocomposite electrode compared to the pure FeCO3 electrode can be attributed to the well dispersed RGO which enhances the electronic conductivity and accommodates the volume change during the conversion reactions. Our study shows that the FeCO3/RGO nanocomposite could be a suitable candidate for high capacity lithium-ion batteries.
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A FeCl2-graphite sandwich composite with Cl doping in graphite layers: a new anode material for high-performance Li-ion batteries.
Nanoscale
PUBLISHED: 10-23-2014
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A composite with FeCl2 nanocrystals sandwiched between Cl-doped graphite layers has been created via a space-confined nanoreactor strategy. This composite can be used as a new type of anode material for Li-ion batteries, which exhibit high reversible capacity and superior rate capability with excellent cycle life.
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Coordination complex pyrolyzation for the synthesis of nanostructured GeO2 with high lithium storage properties.
Chem. Commun. (Camb.)
PUBLISHED: 09-30-2014
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A new (NH4)3H(Ge7O16)(H2O)2.72 precursor-pyrolyzation approach was designed and developed for the facile synthesis of nanostructured GeO2, avoiding the use of any hazardous or expensive germanium compounds. The products show promising anode application in lithium ion batteries with high capacity and excellent cycling stability.
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Selenium/interconnected porous hollow carbon bubbles composites as the cathodes of Li-Se batteries with high performance.
Nanoscale
PUBLISHED: 09-19-2014
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A kind of Se/C nanocomposite is fabricated by dispersing selenium in interconnected porous hollow carbon bubbles (PHCBs) via a melt-diffusion method. Such PHCBs are composed of porous hollow carbon spheres with a size of ?70 nm and shells of ?12 nm thickness interconnected to each other. Instrumental analysis shows that the porous shell of the PHCBs could effectively disperse and sequester most of the selenium, while the inner cavity remains hollow. When evaluated as cathode materials in a carbonate-based electrolyte for Li-Se batteries, the Se/PHCBs composites exhibit significantly excellent cycling performance and a high rate capability. Especially, the Se/PHCBs composite with an optimal content of ?50 wt% selenium (Se50/PHCBs) displays a reversible discharge capacity of 606.3 mA h g(-1) after 120 cycles at 0.1 C charge-discharge rate. As the current density increased from 0.1 to 1 C (678 mA g(-1)), the reversible capacity of the Se50/PHCBs composite can still reach 64% of the theoretical capacity (431.9 mA h g(-1)). These outstanding electrochemical features should be attributed to effective sequestration of Se in the PHCBs, as well as to the ability to accommodate volume variation and enhance the electronic transport by making Se have close contact with the carbon framework.
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Low temperature chemical reduction of fusional sodium metasilicate nonahydrate into a honeycomb porous silicon nanostructure.
Chem. Commun. (Camb.)
PUBLISHED: 05-10-2014
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Honeycomb porous silicon (hp-Si) has been synthesized by a low temperature (200 °C) magnesiothermic reduction of Na2SiO3·9H2O. This process can be regarded as a general synthesis method for other silicide materials. Significantly, hp-Si features excellent electrochemical properties after graphene coating.
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One-step solid state reaction to synthesis of hexagonal BN crystals with rod-like morphology.
J Nanosci Nanotechnol
PUBLISHED: 04-25-2014
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Hexagonal BN crystals have been synthesized from a facile one-step solid state reaction route by sodium tetraphenylborate, hydrazine, zinc powder and sulphur powder as the reactants. The SEM and TEM results showed the BN crystals had the morphology of one-dimensional rod-like shape and with diameters in the range of 100-200 nm and lengths up to several micrometers. Compared with the other reported methods, this route has greatly reduced the reaction temperature. In addition, the growth mechanism of the BN nanorods was discussed in detail. Meanwhile, thermal gravimetric analysis results indicated that the as-prepared BN nanorods have the excellent thermal stability and anti-oxidation properties.
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One-pot hydrothermal synthesis of peony-like Ag/Ag(0.68)V2O5 hybrid as high-performance anode and cathode materials for rechargeable lithium batteries.
Nanoscale
PUBLISHED: 04-02-2014
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A peony-like Ag/Ag0.68V2O5 hybrid assembled from nanosheets with the thickness of 40 nm was synthesized through a one-pot hydrothermal approach from vanadium pentoxide (V2O5), oxalic acid (H2C2O4), and silver nitrate (AgNO3) at 180 °C for 24 h. The hybrid exhibits high performance as both anode and cathode materials for rechargeable lithium batteries. Electrochemical measurements revealed that the as-prepared Ag/Ag0.68V2O5 hybrid displayed excellent cycling stability, especially as an anode material. The resulting anode retains 100% of the initial capacity after 1000 cycles under a current density of 400 mA g(-1). This phenomenon may be attributed to electron conductivity improvement by the existence of metallic silver in the hybrid in addition to the convenient access to lithium ion ingress/egress because of its unique structure.
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Direct large-scale synthesis of 3D hierarchical mesoporous NiO microspheres as high-performance anode materials for lithium ion batteries.
Nanoscale
PUBLISHED: 02-07-2014
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Hierarchically porous materials are an ideal material platform for constructing high performance Li-ion batteries (LIBs), offering great advantages such as large contact area between the electrode and the electrolyte, fast and flexible transport pathways for the electrolyte ions and the space for buffering the strain caused by repeated Li insertion/extraction. In this work, NiO microspheres with hierarchically porous structures have been synthesized via a facile thermal decomposition method by only using a simple precursor. The superstructures are composed of nanocrystals with high specific surface area, large pore volume, and broad pore size distribution. The electrochemical properties of 3D hierarchical mesoporous NiO microspheres were examined by cyclic voltammetry and galvanostatic charge-discharge studies. The results demonstrate that the as-prepared NiO nanospheres are excellent electrode materials in LIBs with high specific capacity, good retention and rate performance. The 3D hierarchical mesoporous NiO microspheres can retain a reversible capacity of 800.2 mA h g(-1) after 100 cycles at a high current density of 500 mA g(-1).
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Hollow MnCo2O4 Submicrospheres with Multilevel Interiors: From Mesoporous Spheres to Yolk-in-Double-Shell Structures.
ACS Appl Mater Interfaces
PUBLISHED: 12-19-2013
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We present a general strategy to synthesize uniform MnCo2O4 submicrospheres with various hollow structures. By using MnCo-glycolate submicrospheres as the precursor with proper manipulation of ramping rates during the heating process, we have fabricated hollow MnCo2O4 submicrospheres with multilevel interiors, including mesoporous spheres, hollow spheres, yolk-shell spheres, shell-in-shell spheres, and yolk-in-double-shell spheres. Interestingly, when tested as anode materials in lithium ion batteries, the MnCo2O4 submicrospheres with a yolk-shell structure showed the best performance among these multilevel interior structures because these structures can not only supply a high contact area but also maintain a stable structure.
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Ferric chloride-Graphite Intercalation Compounds as Anode Materials for Li-ion Batteries.
ChemSusChem
PUBLISHED: 08-16-2013
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Ferric chloride-graphite intercalation compounds (FeCl3 -GICs) with stage?1 and stage?2 structures were synthesized by reacting FeCl3 and expanded graphite (EG) in air in a stainless-steel autoclave. As rechargeable Li-ion batteries, these FeCl3 -GICs exhibit high capacity, excellent cycling stability, and superior rate capability, which could be attributed to their unique intercalation features. This work may enable new possibilities for the fabrication of Li-ion batteries.
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Synthesis of hollow boron nitride nanoboxes with ultrathin walls from cube-like LaB6.
J Nanosci Nanotechnol
PUBLISHED: 08-02-2013
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In this study, cube-like LaB6 was synthesized by Mg coreduction of LaCl3 and B20,3. Then, boron nitride nanoboxes (BNNBs) were produced by nitriding cube-like LaB6, and the latter is not only played as boron source, but also as hard template. The results of characterization (transmission electron microscopy and scanning electron microscopy) indicate that the BN products are hollow structures, the diameter of the nanoboxes is in the range of 200-1000 nm, and the wall thickness of the BN nanoboxes is 16 nm. The specific surface area of BN nanoboxes is 45 m2/g, the pore size is mainly located at 10 nm, and the total pore volume is 0.16 cm3/g. The nitriding of cube-like LaB6 into hollow BNNBs here would provide an alternative route for the synthesis of other hollow BN architectures by other boron-containing materials.
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Iodine assisted low temperature synthesis of 3C-SiC nanostructures and their formation process.
J Nanosci Nanotechnol
PUBLISHED: 07-26-2013
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3C-SiC nanostructures have been synthesized from Si, maltose or glucose and Mg at 120 degrees C in the presence of I2. The as-obtained products are the mixtures of wire-like and tower-shaped SiC nanostructures. Transmission electron microscopy (TEM) and scanning electron microscope (SEM) images show that wire-like nanostructures are formed by the leaning-type packing of triangular nanosheets with the average diameter of 60 nm and tower-shaped nanostructures are formed by the level-type packing of nanosheets with the average diameter of 750 nm and thickness of about 40 nm. The effects of iodine, reaction time and temperature on the morphologies of the final products were also discussed.
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Graphene encapsulated Fe3O4 nanospindles as a superior anode material for lithium-ion batteries.
J Nanosci Nanotechnol
PUBLISHED: 07-19-2013
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Graphene encapsulated Fe3O4 nanospindles were synthesized by a simple hydrothermal method. From field-emission and transmission electron microscopy results, the Fe3O4 nanospindles with the length of about 260 nm are highly encapsulated in graphene matrix. The reversible Li-cycling properties of graphene encapsulated Fe3O4 nanospindles have been evaluated by galvanostatic discharge-charge cycling and cyclic voltammetry. Results show that graphene encapsulated Fe3O4 nanospindles exhibits a high reversible capacity about 745 mA h g(-1) for the first cycle and a stable capacity of about 558 mA h g(-1) for up to 200th cycle in the voltage range of 0.01-3.0 V at a current density of 100 mA g(-1), indicating excellent cycling stability. The graphene in the composite materials could act not only as lithium storage active materials, but also as an electronically conductive matrix to improve the electrochemical performance of Fe3O4.
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MnO@carbon core-shell nanowires as stable high-performance anodes for lithium-ion batteries.
Chemistry
PUBLISHED: 05-10-2013
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A facile method is presented for the large-scale preparation of rationally designed mesocrystalline MnO@carbon core-shell nanowires with a jointed appearance. The nanostructures have a unique arrangement of internally encapsulated highly oriented and interconnected MnO nanorods and graphitized carbon layers forming an external coating. Based on a comparison and analysis of the crystal structures of MnOOH, Mn2 O3 , and MnO@C, we propose a sequential topotactic transformation of the corresponding precursors to the products. Very interestingly, the individual mesoporous single-crystalline MnO nanorods are strongly interconnected and maintain the same crystallographic orientation, which is a typical feature of mesocrystals. When tested for their applicability to Li-ion batteries (LIB), the MnO@carbon core-shell nanowires showed excellent capacity retention, superior cycling performance, and high rate capability. Specifically, the MnO@carbon core-shell nanostructures could deliver reversible capacities as high as 801?mA?h?g(-1) at a high current density of 500?mA?g(-1) , with excellent electrochemical stability after testing over 200 cycles, indicating their potential application in LIBs. The remarkable electrochemical performance can mainly be attributed to the highly uniform carbon layer around the MnO nanowires, which is not only effective in buffering the structural strain and volume variations of anodes during repeated electrochemical reactions, but also greatly enhances the conductivity of the electrode material. Our results confirm the feasibility of using these rationally designed composite materials for practical applications. The present strategy is simple but very effective, and appears to be sufficiently versatile to be extended to other high-capacity electrode materials with large volume variations and low electrical conductivities.
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Controlled synthesis of PbTe nanorods and nanotubes.
J Nanosci Nanotechnol
PUBLISHED: 05-08-2013
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A hydrothermal route has been developed to synthesize lead telluride (PbTe) nanostructures through the reaction between Pb(CH3COO)2 and Na2TeO3. When the surfactant poly(vinyl pyrrolidone) (PVP) was introduced into the solution, uniform PbTe nanorods with a diameter of about 30 nm could be prepared, while absent of PVP, PbTe nanotubes could be synthesized. Furthermore, some interesting Y-, V-, crisscross-shaped PbTe nanotubes were reported for the first time. The resulting materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution TEM (HRTEM). Two different mechanisms are identified to explain the formation of the nanorods and nanotubes herein. A surfactant-assisted oriental attachment mechanism is explained to describe the formation of PbTe nanorods, whereas, we deduce PbTe nanotubes follow a self-generated template route.
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Shape controlled hydrothermal synthesis and characterization of LiFePO4 for lithium ion batteries.
J Nanosci Nanotechnol
PUBLISHED: 05-08-2013
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Various LiFePO4 microstructures were synthesized via hydrothermal or solvothermal routes using different additives. In an aqueous solution, LiFePO4 spindles whose length was about 2 microm were obtained with the assistance of polyvinyl pyrrolidone (PVP). As PVP and P2O7(4-) added in water, ellipsoidal LiFePO4 particles which composed of nanoparticles around 100 nm in diameter were obtained. If the additive was cetyltrimethyl ammonium bromide (CTAB), sheet-like LiFePO4 crystals with the width of 100 nm were prepared. In the mixed solvents of water together with ethanol or acetylacetone, when adding CTAB or polyethylene glycol (20000), LiFePO4 plates or nanoparticles were obtained. The ellipsoidal LiFePO4 had the best electrochemical properties among all these products. It is found that the annealed samples were significantly better than the corresponding unannealed ones. Take the ellipsoidal LiFePO4 for example, the initial discharge capacity of annealed (161 mAh/g) was much higher than the unannealed ones (85 mAh/g) at 0.1 C and the former cell still could deliver a capacity of 143 mAh/g after 30 cycles.
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Facile synthesis and application of CuS nanospheres in aqueous and organic lithium ion batteries.
J Nanosci Nanotechnol
PUBLISHED: 05-08-2013
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Monodispersed CuS nanospheres with a diameter of about 200 nm consisted of nanoplates have been hydrothermally synthesized via a facile process without any surfactant at 120 degrees C. The morphologies of the hierarchical CuS nanospheres were explored by X-ray diffraction, field emission scanning and transmission electron microscopy. In addition, CuS nanospheres cathode material for lithium-ion batteries were studied both in Organic and Aqueous phase. In organic electrolyte, the discharge capacity at first cycle with a cutoff voltage of 3-1.5 V is up to 628 mAh/g. When the voltage range is fixed from 1.8 to 2.6 V, the first discharge capacity reaches 225 mAh/g. After 30 cycles the discharge capacity has still kept at 90 mAh/g. On the other hand, it is well worth noting that here we first report the electrochemical behavior of CuS in aqueous lithium-ion batteries. In aqueous phase, different from other materials which have a drastic decay, it still keeps its initiative capacity 45 mAh/g after 100 cycles.
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Synthesis of Fe3O4@C core-shell nanorings and their enhanced electrochemical performance for lithium-ion batteries.
Nanoscale
PUBLISHED: 03-21-2013
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Fe3O4@C core-shell nanorings (R-Fe3O4@C) were fabricated by a synchronous reduction and carbon deposition process. As the anodes for lithium-ion batteries, these R-Fe3O4@C exhibit a high capacity, excellent cycling stability and good rate performance. This ring-shaped core-shell nanostructure design may pave the way to enhance electrochemical performances of electrode materials.
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Facile synthesis of loaf-like ZnMn?O? nanorods and their excellent performance in Li-ion batteries.
Nanoscale
PUBLISHED: 02-14-2013
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Binary transition metal oxides have been attracting extensive attention as promising anode materials for lithium-ion batteries, due to their high theoretical specific capacity, superior rate performance and good cycling stability. Here, loaf-like ZnMn2O4 nanorods with diameters of 80-150 nm and lengths of several micrometers are successfully synthesized by annealing MnOOH nanorods and Zn(OH)2 powders at 700 °C for 2 h. The electrochemical properties of the loaf-like ZnMn2O4 nanorods as an anode material are investigated in terms of their reversible capacity, and cycling performance for lithium ion batteries. The loaf-like ZnMn2O4 nanorods exhibit a reversible capacity of 517 mA h g(-1) at a current density of 500 mA g(-1) after 100 cycles. The reversible capacity of the nanorods still could be kept at 457 mA h g(-1) even at 1000 mA g(-1). The improved electrochemical performance can be ascribed to the one-dimensional shape and the porous structure of the loaf-like ZnMn2O4 nanorods, which offers the electrode convenient electron transport pathways and sufficient void spaces to tolerate the volume change during the Li(+) intercalation. These results suggest the promising potential of the loaf-like ZnMn2O4 nanorods in lithium-ion batteries.
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A facile route to synthesize multiporous MnCo2O4 and CoMn2O4 spinel quasi-hollow spheres with improved lithium storage properties.
Nanoscale
PUBLISHED: 02-01-2013
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A facile and general way for the synthesis of porous and hollow complex oxides is highly desirable owing to their significant applications for energy storage and other fields. In this contribution, uniform Mn(0.33)Co(0.67)CO(3) and Co(0.33)Mn(0.67)CO(3) microspheres are firstly fabricated solvothermally just by tuning the molar ratio of Mn and Co. Subsequently, the growth of multiporous MnCo(2)O(4) and CoMn(2)O(4) quasi-hollow microspheres by topotactic chemical transformation from the corresponding precursors are realized through a non-equilibrium heat treatment process. Topotactic conversion further demonstrated that the much larger CoMn(2)O(4) pores than those of MnCo(2)O(4) are possibly due to the longer transfer distance of ions. When evaluated as anode materials for LIBs (lithium ion batteries), after 25 cycles at a current density of 200 mA g(-1), the resultant MnCo(2)O(4) and CoMn(2)O(4) quasi-hollow microspheres possessed reversible capacities of 755 and 706 mA h g(-1), respectively. In particular, the MnCo(2)O(4) samples could deliver a reversible capacity as high as 610 mA h g(-1) even at a higher current density of 400 mA g(-1) with excellent electrochemical stability after 100 cycles of testing, indicating its potential application in LIBs. We believe that such good performance results from the appropriate pore size and quasi-hollow nature of MnCo(2)O(4) microspheres, which can effectively buffer the large volume variation of anodes based on the conversion reaction during Li(+) insertion/extraction. The present strategy is simple but very effective, and due to its versatility, it can be extended to other binary, even ternary complex metal oxides with high-performance in LIBs.
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Enhanced lithium storage performances of hierarchical hollow MoS? nanoparticles assembled from nanosheets.
ACS Appl Mater Interfaces
PUBLISHED: 01-31-2013
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MoS(2), because of its layered structure and high theoretical capacity, has been regarded as a potential candidate for electrode materials in lithium secondary batteries. But it suffers from the poor cycling stability and low rate capability. Here, hierarchical hollow nanoparticles of MoS(2) nanosheets with an increased interlayer distance are synthesized by a simple solvothermal reaction at a low temperature. The formation of hierarchical hollow nanoparticles is based on the intermediate, K(2)NaMoO(3)F(3), as a self-sacrificed template. These hollow nanoparticles exhibit a reversible capacity of 902 mA h g(-1) at 100 mA g(-1) after 80 cycles, much higher than the solid counterpart. At a current density of 1000 mA g(-1), the reversible capacity of the hierarchical hollow nanoparticles could be still maintained at 780 mAh g(-1). The enhanced lithium storage performances of the hierarchical hollow nanoparticles in reversible capacities, cycling stability and rate performances can be attributed to their hierarchical surface, hollow structure feature and increased layer distance of S-Mo-S. Hierarchical hollow nanoparticles as an ensemble of these features, could be applied to other electrode materials for the superior electrochemical performance.
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High electrochemical performance of monodisperse NiCo?O? mesoporous microspheres as an anode material for Li-ion batteries.
ACS Appl Mater Interfaces
PUBLISHED: 01-16-2013
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Binary metal oxides have been regarded as ideal and potential anode materials, which can ameliorate and offset the electrochemical performance of the single metal oxides, such as reversible capacity, structural stability and electronic conductivity. In this work, monodisperse NiCo(2)O(4) mesoporous microspheres are fabricated by a facile solvothermal method followed by pyrolysis of the Ni(0.33)Co(0.67)CO(3) precursor. The Brunauer-Emmett-Teller (BET) surface area of NiCo(2)O(4) mesoporous microspheres is determined to be about 40.58 m(2) g(-1) with dominant pore diameter of 14.5 nm and narrow size distribution of 10-20 nm. Our as-prepared NiCo(2)O(4) products were evaluated as the anode material for the lithium-ion-battery (LIB) application. It is demonstrated that the special structural features of the NiCo(2)O(4) microspheres including uniformity of the surface texture, the integrity and porosity exert significant effect on the electrochemical performances. The discharge capacity of NiCo(2)O(4) microspheres could reach 1198 mA h g(-1) after 30 discharge-charge cycles at a current density of 200 mA g(-1). More importantly, when the current density increased to 800 mA·g(-1), it can render reversible capacity of 705 mA h g(-1) even after 500 cycles, indicating its potential applications for next-generation high power lithium ion batteries (LIBs). The superior battery performance is mainly attributed to the unique micro/nanostructure composed of interconnected NiCo(2)O(4) nanocrystals, which provides good electrolyte diffusion and large electrode-electrolyte contact area, and meanwhile reduces volume change during charge/discharge process. The strategy is simple but very effective, and because of its versatility, it could be extended to other high-capacity metal oxide anode materials for LIBs.
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General synthesis of carbon nanocages and their adsorption of toxic compounds from cigarette smoke.
Nanoscale
PUBLISHED: 07-15-2011
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Carbon nanocages (CNCs) have been synthesized through a simple approach using different alcohols and ferrous oxalate as reactants at 550 °C for 12 h in a sealed autoclave. The lengths of the sides of the CNCs are about 200-350 nm and the wall thicknesses are about 10-15 nm. The formation mechanism of the CNCs is also discussed, based on the experimental results. These CNCs show excellent removal efficiency for phenolic compounds, ammonia, and total particulate matter from cigarette smoke. The adsorption capability of CNCs prepared from ethanol is much higher than that of other samples. For example, the efficiency of 5 mg CNCs (ethanol) for removing the six phenolic compounds p-dihydroxybenzene, m-dihydroxybenzene, o-dihydroxybenzene, phenol, m-cresol, and o-cresol can reach 57.31%, 62.25%, 65.58%, 75.95%, 54.34% and 59.43%, respectively, while that of the commercial activated carbon (5 mg) can only reach 29.02%, 33.93%, 35.00%, 36.00%, 20.33% and 36.19%, respectively, under the same conditions.
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Preparation of LiCoO2 concaved cuboctahedra and their electrochemical behavior in lithium-ion battery.
Dalton Trans
PUBLISHED: 06-24-2011
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LiCoO(2) concaved cuboctahedra with a size of about 1.0 ?m were hydrothermally prepared from CoCO(3) and LiOH·H(2)O at 150 °C. Field-emitting scanning electron microscope (FESEM) images show that the cuboctahedra consisted of four hexagonal plates, with angles of 70.5° in neighboring plates. Electron diffraction (ED) patterns of the hexagonal plates show 1? 0? 0 diffraction of LiCoO(2) in rhombohedral phase and 2?2?0 diffraction in spinel phase, which means LiCoO(2) concaved cuboctahedra are comprised of two intergrown phases. The electrochemical performance of these concaved cuboctahedra of LiCoO(2) at a rate of 0.5 C demonstrated first run charge/discharge capacities of 155 and 141 mAh g(-1) and a stable discharge capacity of 114 mAh g(-1) after 100 cycles. After that, FESEM images show the LiCoO(2) concaved cuboctahedra have undergone no significant change. At a temperature of 120 °C and under the same conditions, only a small amount of LiCoO(2) concaved cuboctahedron appeared. As the temperature rose to 180 °C, flower-like LiCoO(2) microstructures with a size of about 1.0 ?m were formed, constructed of irregular plates. The electrochemical performance of the products prepared at 120 °C and 180 °C indicates lower stability than that of LiCoO(2) concaved cuboctahedra.
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Synthetic methodologies for carbon nanomaterials.
Adv. Mater. Weinheim
PUBLISHED: 06-08-2010
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Carbon nanomaterials have advanced rapidly over the last two decades and are among the most promising materials that have already changed and will keep on changing human life. Development of synthetic methodologies for these materials, therefore, has been one of the most important subjects of carbon nanoscience and nanotechnology, and forms the basis for investigating the physicochemical properties and applications of carbon nanomaterials. In this Research News article, several synthetic strategies, including solvothermal reduction, solvothermal pyrolysis, hydrothermal carbonization, and soft-chemical exfoliation are specifically discussed and highlighted, which have been developed for the synthesis of novel carbon nanomaterials over the last decade.
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Sulfur-assisted synthesis of nitride nanocrystals.
Dalton Trans
PUBLISHED: 02-05-2010
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A series of nitrides (TiN, ZrN, BN, AlN) were prepared by using the corresponding elements (Ti, Zr, B, Al), NaN(3) and sulfur as starting materials in a stainless steel autoclave at 250 degrees C. Sulfur was used to facilitate the exothermic reaction between NaN(3) and sulfur (at 250 degrees C) and the final formation of nitrides. The treatment temperature affected the growth of the nitride crystals, for example, diversified morphologies of TiN nanocrystals were formed in different temperature ranges: grain and truncated octahedron (250 degrees C), octahedron (>300 degrees C), and dendrite (>400 degrees C). Through similar processes, other nitrides (for example, TiN, AlN, Si(3)N(4)) could also be produced by employing NaNH(2) and additives (such as iodine or N-aminothiourea instead of sulfur) in low temperatures.
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A convenient solvothermal synthesis route to metal phosphides with a shape of hollow nanospheres.
J Nanosci Nanotechnol
PUBLISHED: 11-26-2009
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InP hollow nanospheres with an average size of 550 nm and shell thickness of about 110 nm were solvothermally synthesized in EA (ethanolamine)-H2O binary solution at 190 degrees C for 36 h. The shells of InP hollow nanospheres were composed of small nanoparticles. The similar route has been extended to prepare Cd3P2, Cu3P and Sn4P3 hollow nanospheres in 150-190 degrees C for 24-36 h.
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The synthesis of nanostructured SiC from waste plastics and silicon powder.
Nanotechnology
PUBLISHED: 08-12-2009
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Waste plastics constitute a growing environmental problem. Therefore, the treatment of waste plastics should be considered. Here we synthesize 3C-SiC nanomaterials coexisting with amorphous graphite particles utilizing waste plastics and Si powder at 350-500 degrees C in a stainless steel autoclave. 3C-SiC could be finally obtained after refluxing with aqueous HClO(4) (70 wt%) at 180 degrees C. X-ray powder diffraction patterns indicate that the product is 3C-SiC with the calculated lattice constant a = 4.36 A. Transmission electron microscopy (TEM) images show that the SiC samples presented two morphologies: hexagonal platelets prepared by the waste detergent bottles or beverage bottles and nanowires prepared by waste plastic bags respectively. The corresponding selected area electron diffraction (SAED) pattern indicates that either the entire hexagonal platelet or the nanowire is single crystalline. High-resolution TEM shows the planar surfaces of the SiC platelet correspond to {111} planes; the lateral surfaces are {110} planes and the preferential growth direction of the nanowires is along [111]. The output of SiC was approximately 39% based on the amount of Si powder.
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Hydrothermal synthesis of microscaled Cu@C polyhedral composites and their sensitivity to convergent electron beams.
Langmuir
PUBLISHED: 05-27-2009
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Copper microparticles (2-5 um) encapsulated in carbonaceous shell polyhedral composites were mildly prepared via a one-pot hydrothermal process using copper nitrate, glucose, and sodium citrate at 150 degrees C, in which the glucose was found to play reducer and graphite source roles during the formation of these core-shell-like composites. Thermal stability results indicated that their weights remain almost unchanged below 240 degrees C in ambient atmosphere. It is interesting that the copper microparticles could be partially released out and translated into monodisperse Cu nanoparticles around the initial composites under the convergent electron beams in a transmission electron microscope (TEM). This phenomenon is an appealing discovery, which might endow the Cu@C composite with new functions; for example, it might be applied as a sensitive detector for the leakage of electron beams or other substances for the sake of being a safeguard. In addition, the corresponding hollow carbonaceous polyhedra were also obtained after the acid treatment, which might be used as a template to fabricate other kinds of polyhedra.
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Synthesis and characterization of hexagonal NiTe2 nanoplates.
J Nanosci Nanotechnol
PUBLISHED: 05-15-2009
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Single-crystalline NiTe2 nanoplates have been synthesized on a large scale through a hydrothermal reaction of Ni(CH3COO)2 and TeO2 at 210 degrees C for 48 h. The NiTe2 nanoplates have hexagonal shape. The average edge sizes and thicknesses of nanoplates are 350 nm and 85 nm, respectively. Here, Ethylenediaminetetraacetic acid (EDTA) is employed as a chelating agent. Furthermore, EDTA plays crucial roles in controlling phase composition and morphology of the resultant products.
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Controlled Growth of Carbon Spheres Through the Mg-Reduction Route.
Nanoscale Res Lett
PUBLISHED: 04-09-2009
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Hollow spheres, hollow capsules and solid spheres of carbon were selectively synthesized by Mg-reduction of hexachlorobutadiene at appropriate reaction conditions. X-ray powder diffraction and Raman spectra reveal that the as-prepared materials have a well-ordered structure. A possible formation mechanism has been proposed.
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Controllable synthesis of mesoporous Co3O4 nanostructures with tunable morphology for application in supercapacitors.
Chemistry
PUBLISHED: 04-08-2009
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Novel and complex mesoporous 2D and 3D architectures of the oxide semiconductor Co(3)O(4), including nanosheets, nearly monodisperse microspheres that are self-assembled from nanosheets, and copper-coin-like nanosheets, have been synthesized through a facile binary-solution route and sequential thermal decomposition at atmospheric pressure. The influence of different reaction conditions on the morphology of the products has been discussed in detail. The results revealed that the volume ratio of H(2)O and ethanolamine (EA) play a crucial role in the morphology of the precursor. The thermal decomposition of the corresponding precursor leads to the formation of the mesoporous structure. The products have been characterized by X-ray diffraction techniques, field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and Raman spectroscopy. The electrochemical properties of the Co(3)O(4) electrodes were investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge measurements. The electrochemical experiments revealed that the specific capacitance of the Co(3)O(4) nanosheets was higher than that of the Co(3)O(4) microspheres in a KOH electrolyte solution (3 m). Furthermore, the Co(3)O(4) nanosheet electrodes exhibited good rate capabilities, and maintained 93% of the initial capacity at a current density of 5 mA cm(-2) in a KOH (3 m) electrolyte solution. The results show that Co(3)O(4) nanosheets might have potential applications as electrode materials for supercapacitors.
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MnCO3 microstructures assembled with nanoparticles: shape-controlled synthesis and their application for Li-ion batteries.
J Nanosci Nanotechnol
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MnCO3 ellipsoids and twinborn spheres have been synthesized by a hydrothermal process and a room temperature synthesis approach, respectively. The structures and morphologies of the products are investigated by X-ray powder diffraction (XRD) and field emission-scanning electron microscopy (FE-SEM). XRD patterns indicate the MnCO3 ellipsoids display higher crystallinity than twinborn spheres. SEM images show that both the MnCO3 ellipsoids and twinborn spheres have a similar size of about 1 microm and consist of nanoscale primary particles. Brunauer-Emmett-Teller (BET) surface areas of MnCO3 ellipsoids and twinborn spheres are 33.93 and 59.35 m2/g, respectively. Furthermore, the lithium storage properties of these MnCO3 samples with distinct morphologies have been investigated. When used as anode materials in lithium-ion batteries, MnCO3 ellipsoids and twinborn spheres exhibit the initial discharge capacities of 1375 and 1650 mAh/g, respectively. After charged/discharged for 50 cycles at a current density of 500 mA/g, the remaining discharge capacities for MnCO3 ellipsoids and twinborn spheres are 663 and 305 mAh/g, respectively.
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NbN and NaNbN2 particles: selective solid state synthesis and conduction performance.
J Nanosci Nanotechnol
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Starting from Nb2O5, NaN3 and different metallic reductants such as magnesium or aluminum, cubic NbN and hexagonal NaNbN2 were selectively synthesized in a stainless steel autoclave at 400-700 degrees C. When magnesium was used as a metallic reductant, NbN can be synthesized at 400 degrees C for 10 h. If the metallic reductant was replaced by aluminum, NaNbN2 was obtained at 700 degrees C for 40 h. The structures and morphologies of the samples were derived from X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and field emission-scanning electron microscopy (FE-SEM). FE-SEM images showed that the NbN sample consisted of particles with an average size of about 100 nm, and the NaNbN2 sample is composed of with an average size of 500 nm. Furthermore, the electric resistivity of the obtained samples reveals the obtained NbN sample is a superconductor with transition temperature of 17 K, and the obtained NaNbN2 sample can be classified as a semiconductor.
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Facile synthesis of novel tunable highly porous CuO nanorods for high rate lithium battery anodes with realized long cycle life and high reversible capacity.
Nanoscale
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Various CuO nanostructures have been well studied as anode materials for lithium ion batteries (LIBs); however, there are few reports on the synthesis of porous CuO nanostructures used for anode materials, especially one-dimensional (1D) porous CuO. In this work, novel 1D highly porous CuO nanorods with tunable porous size were synthesized in large-quantities by a new, friendly, but very simple approach. We found that the pore size could be controlled by adjusting the sintering temperature in the calcination process. With the rising of calcination temperature, the pore size of CuO has been tuned in the range of ?0.4 nm to 22 nm. The porous CuO materials have been applied as anode materials in LIBs and the effects of porous size on the electrochemical properties were observed. The highly porous CuO nanorods with porous size in the range of ?6 nm to 22 nm yielded excellent high specific capacity, good cycling stability, and high rate performance, superior to that of most reported CuO nanocomposites. The CuO material delivers a high reversible capacity of 654 mA h g(-1) and 93% capacity retention over 200 cycles at a rate of 0.5 C. It also exhibits excellent high rate capacity of 410 mA h g(-1) even at 6 C. These results suggest that the facile synthetic method of producing a tunable highly porous CuO nanostructure can realize a long cycle life with high reversible capacity, which is suitable for next-generation high-performance LIBs.
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Solvothermal synthesis of 3D BiOCl microstructures and their electrochemical hydrogen storage behavior.
J Nanosci Nanotechnol
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Bi-based layered materials, at present, serve as the potential candidates for the application of hydrogen storage. In our study, several 3D BiOCl microstructures, such as 2500 nm peonies, 1000 nm ball-flowers, and 3000 nm rough spheres are selectively and solvothermally prepared at 180 degrees C. These microstructures are composed of nanoplate with size of -1000 nm, -300 nm and -200 nm, respectively, the growth surface of which are all (001). Electrochemical hydrogen storage capacities of these microstructures are investigated in Ni/H battery model. It is found that rough spheres could store 0.52 wt% hydrogen related to a discharge capacity of 140 mAh x g(-1) at a current density of 50 mA x g(-1). The hydrogen storage of ball-flowers and peonies is 0.49 wt% (133 mAh x g(-1)) and 0.32 wt% (85 mAh x g(-1)). Brunauer-Emmett-Teller (BET) surface areas of rough spheres, ball-flowers and peonies are 35.0 m2 x g(-1), 33.7 m2 x g(-1), and 19.2 m2 x g(-1), respectively. In addition, the hydrogen storage study of BiOCI microstructure composed of nanoplates with exposed facet perpendicular to [221] axis indicates that hydrogen enters into the interlayer.
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Room-temperature synthesis of BiOBr sub-microflowers and their photocatalytic properties.
J Nanosci Nanotechnol
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Flower-like BiOBr sub-microstructures about 500 nm in diameter have been synthesized in the presence of tetraethylammonium bromide (TEAB) via a solution route at room temperature. SEM observation shows that these sub-microflowers are composed of nanoflakes with the thickness of 20 nm. The photocatalytic activities of flower-like BiOBr were evaluated by the degradation of methyl orange (MO) and phenol under visible-light and UV-light irradiation, which presented the efficiencies up to 97% within 1.5 h and 45% within 4 h, respectively.
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Branched mesoporous Mn3O4 nanorods: facile synthesis and catalysis in the degradation of methylene blue.
Chemistry
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Branched MnOOH nanorods with diameters in the range of 50-150 nm and lengths of up to tens of micrometers were prepared by using potassium permanganate (KMnO(4)) and PEG 400 (PEG=polyethylene glycol) as starting materials through a simple hydrothermal process at 160 °C. After annealing at 300 °C under a N(2) atmosphere for 5 h, MnOOH nanorods became gradually dehydrated and transformed into mesoporous Mn(3)O(4) nanorods with a slight size-shrinking. The as-obtained mesoporous Mn(3)O(4) nanorods had an average surface area of 32.88 m(2) g(-1) and a mean pore size of 3.7 nm. Through tuning the experimental parameters, such as the annealing atmosphere and temperature, ?-MnO(2), Mn(2)O(3), Mn(3)O(4), MnO, and Mn(5)O(8) were selectively produced. Among these structures, mesoporous Mn(3)O(4) nanorods were efficient for the catalytic degradation of methylene blue (MB) in the presence of H(2)O(2) at 80 °C.
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Synthesis of Mn2O3 nanomaterials with controllable porosity and thickness for enhanced lithium-ion batteries performance.
Nanoscale
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Mn2O3 has been demonstrated to be a promising electrode material for lithium-ion batteries. Thus, the fabrication of Mn2O3 nanomaterials with high specific capacity and cycling stability is greatly desired. Here we report a simple but effective method to synthesis Mn2O3 nanomaterials from a Mn(OH)2 precursor, which was prepared from manganese acetate in ethylene glycol and water at 180 °C for 12 h. The morphology and sheet thickness of Mn(OH)2 precursor could be tuned by controlling the ethylene glycol/H2O volume ratio, resulting in a further tunable morphology and sheet thickness of the porous Mn2O3 nanomaterials. In the electrochemical tests the prepared Mn2O3 nanomaterials, with the porous architecture and thin thickness exhibited a high and stable reversible capacity, indicating that both small thickness and porous sheets structure are crucial for improving the electrochemical performance of Mn2O3 in terms of specific capacity and stability.
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