Co-Modification of commercial TiO2 anode by combining a solid electrolyte with pitch-derived carbon to boost cyclability and rate capabilities.

The bad electrochemical performance circumscribes the application of commercial TiO2 (c-TiO2) anodes in Li-ion batteries. Carbon coating could ameliorate the electronic conductivity of TiO2, but the ionic conductivity is still inferior. Herein, a co-modification method was proposed by combining the solid electrolyte of lithium magnesium silicate (LMS) with pitch-derived carbon to concurrently meliorate the electronic and ionic conductivities of c-TiO2. The homogeneous mixtures were heated at 750 °C, and the co-modified product with suitable amounts of LMS and carbon demonstrates cycling capacities of 256.8, 220.4, 195.9, 176.4, and 152.0 mA h g-1 with multiplying current density from 100 to 1600 mA g-1. Even after 1000 cycles at 500 mA g-1, the maintained reversible capacity was 244.8 mA h g-1. The superior rate performance and cyclability correlate closely with the uniform thin N-doped carbon layers on the surface of c-TiO2 particles to favor the electrical conduction, and with the ion channels in LMS as well as the cation exchangeability of LMS to facilitate the Li+ transfer between the electrolyte, carbon layers, and TiO2 particles. The marginal amount of fluoride in LMS also contributes to the excellent cycling stability of the co-modified c-TiO2.

A uniform few-layered carbon coating derived from self-assembled carboxylate monolayers capable of promoting the rate properties and durability of commercial TiO2.

The poor cyclability and rate property of commercial TiO2 (c-TiO2) hinder its utilization in lithium-ion batteries (LIBs). Coating carbon is one of the ways to ameliorate the electrochemical performance. However, how to effectively form a uniform thin carbon coating is still a challenge. On the basis of the strong interaction of the TiO2 surface with carboxyl groups, herein a new tactic to achieve uniform and thin carbon layers on the c-TiO2 particles was proposed. When mixing c-TiO2 with citric acid containing carboxyl groups in deionized water, the high-affinity adsorption of TiO2 for carboxyl groups resulted in self-assembled carboxylate monolayers on the surface of TiO2 which evolved into a uniform few-layered amorphous carbon coating during carbonizing at 750 °C. The product derived from the mixture of c-TiO2 and citric acid with a mass ratio of 1 : 0.3 exhibits the optimal performance, revealing a high specific capacity (256.6 mA h g-1 after 50 cycles at 0.1 A g-1) and outstanding cycling stability (retaining a capacity of 160.0 mA h g-1 after 1000 cycles at 0.5 A g-1). The greatly enhanced capacity and cyclability correlate with the uniform few-layered carbon coating which not only ameliorates the electronic conductivity of c-TiO2 but also avoids the reduction in ionic conductivity caused by thick carbon layers and redundant carbon.

Combined Modification of Dual-Phase Li4Ti5O12-TiO2 by Lithium Zirconates to Optimize Rate Capabilities and Cyclability.

The low electrical conductivity and ordinary lithium-ion transfer capability of Li4Ti5O12 restrict its application to some degree. In this work, dual-phase Li4Ti5O12-TiO2 (LTOT) was modified by composite zirconates of Li2ZrO3, Li6Zr2O7 (LZO) to boost the rate capabilities and cyclability. When the homogeneous mixture of LiNO3, Zr(NO3)4·5H2O and LTOT was roasted at 700 °C for 5 h, the obtained composite achieved a superior reversible capacity of 183.2 mAh g-1 to the pure Li4Ti5O12 after cycling at 100 mA g-1 for 100 times due to the existence of a scrap of TiO2. Meanwhile, when the composite was cycled by consecutively doubling the current density between 100 and 1600 mA g-1, the corresponding reversible capacities are 183.2, 179.1, 176.5, 173.3, and 169.3 mAh g-1, signifying the prominent rate capabilities. Even undergoing 1400 charge/discharge cycles at 500 mA g-1, a reversible capacity of 144.7 mAh g-1 was still attained, denoting splendid cyclability. From a series of comparative experiments and systematic characterizations, the formation of LZO meliorated both the Li+ migration kinetics and electrical conductivity on account of the concomitant superficial Zr4+ doping, responsible for the comprehensive elevation of the electrochemical performance.

Uniform Surface Modification of Li2ZnTi3O8 by Liquated Na2MoO4 To Boost Electrochemical Performance.

Poor ionic and electronic conductivities are the key issues to affect the electrochemical performance of Li2ZnTi3O8 (LZTO). In view of the water solubility, low melting point, good electrical conductivity, and wettability to LZTO, Na2MoO4 (NMO) was first selected to modify LZTO via simply mixing LZTO in NMO water solution followed by calcining the dried mixture at 750 °C for 5 h. The electrochemical performance of LZTO could be enhanced by adjusting the content of NMO, and the modified LZTO with 2 wt % NMO exhibited the most excellent rate capabilities (achieving lithiation capacities of 225.1, 207.2, 187.1, and 161.3 mAh g-1 at 200, 400, 800, and 1600 mA g-1, respectively) as well as outstanding long-term cycling stability (delivering a lithiation capacity of 229.0 mAh g-1 for 400 cycles at 500 mA g-1). Structure and composition characterizations together with electrochemical impedance spectra analysis demonstrate that the molten NMO at the sintering temperature of 750 °C is beneficial to diffuse into the LZTO lattices near the surface of LZTO particles to yield uniform modification layer, simultaneously ameliorating the electronic and ionic conductivities of LZTO, and thus is responsible for the enhanced electrochemical performance of LZTO. First-principles calculations further verify the substitution of Mo6+ for Zn2+ to realize doping in LZTO. The work provides a new route for designing uniform surface modification at low temperature, and the modification by NMO could be extended to other electrode materials to enhance the electrochemical performance.

Ionic Conductor of Li2SiO3 as an Effective Dual-Functional Modifier To Optimize the Electrochemical Performance of Li4Ti5O12 for High-Performance Li-Ion Batteries.

Ionic conductor of Li2SiO3 (LSO) was used as an effective modifier to fabricate surface-modified Li4Ti5O12 (LTO) via simply mixing followed by sintering at 750 °C in air. The electrochemical performance of LTO was enhanced by merely adjusting the mass ratio of LTO/LSO, and the LTO/LSO composite with 0.51 wt % LSO exhibited outstanding rate capabilities (achieving reversible capacities of 163.8, 157.6, 153.1, 147.0, and 137.9 mAh g-1 at 100, 200, 400, 800, and 1600 mA g-1, respectively) and remarkable long-term cycling stability (120.2 mAh g-1 after 2700 cycles with a capacity fading rate of only 0.0074% per cycle even at 500 mA g-1). Combining structural characterization with electrochemical analysis, the LSO coating coupled with the slight doping effect adjacent to the LTO surface contributes to the enhancement of both electronic and ionic conductivities of LTO.

Simple preparation of carbon nanofibers with graphene layers perpendicular to the length direction and the excellent li-ion storage performance.

Sulfur-containing carbon nanofibers with the graphene layers approximately vertical to the fiber axis were prepared by a simple reaction between thiophene and sulfur at 550 °C in stainless steel autoclaves without using any templates. The formation mechanism was discussed briefly, and the potential application as anode material for lithium-ion batteries was tentatively investigated. The carbon nanofibers exhibit a stable reversible capacity of 676.8 mAh/g after cycling 50 times at 0.1 C, as well as the capacities of 623.5, 463.2, and 365.8 mAh/g at 0.1, 0.5, and 1.0 C, respectively. The excellent electrochemical performance could be attributed to the effect of sulfur. On one hand, sulfur could improve the reversible capacity of carbon materials due to its high theoretical capacity; on the other hand, sulfur could promote the formation of the unique carbon nanofibers with the graphene layers perpendicular to the axis direction, favorable to shortening the Li-ion diffusion path.

Prussion blue-supported annealing chemical reaction route synthesized double-shelled Fe2O3/Co3O4 hollow microcubes as anode materials for lithium-ion battery.

Fe2O3/Co3O4 double-shelled hierarchical microcubes were synthesized based on annealing of double-shelled Fe4[Fe(CN)6]3/Co(OH)2 microcubes, using Co(AC)2 as a Co(2+) source to react with OH(-) generated from the reaction of ammonium hydroxide and water. The robust Fe2O3 hollow microcube at the inner layer not only displays a good electronic conductivity but also acts as stable supports for hierarchical Co3O4 outside shell consisting of nanosized particles. The double-shelled hollow structured Fe2O3/Co3O4 nanocomposites display obvious advantages as anode materials for LIBs. The hollow structure can ensure the presence of additional free volume to alleviate the structural strain associated with repeated Li(+)-insertion/extraction processes, as well as a good contact between electrode and electrolyte. The robust Fe2O3 shell acts as a strong support for Co3O4 nanoparticles and efficiently prevents the aggregation of the Co3O4 nanoparticles. Furthermore, the charge transfer resistance can be greatly decreased because of the formation of interface between Fe2O3 and Co3O4 shells and a relative good electronic conductivity of Fe2O3 than that of Co3O4, resulting in a decrease of charge transfer resistance for improving the electron kinetics for the hollow double-shelled microcube as anode materials for LIBs. The Fe2O3/Co3O4 nanocomposite anode with a molar ratio of 1:1 for Fe:Co exhibits the best cycle performance, displaying an initial Coulombic efficiency of 74.4%, delivering a specific capacity of 500 mAh g(-1) after 50 cycles at a current density of 100 mA g(-1), 3 times higher than that of pure Co3O4 nanoparticle sample. The great improvement of the electrochemical performance of the synthesized Fe2O3/Co3O4 double-shelled hollow microcubes can be attributed to the unique microstructure characteristics and synergistic effect between the inner shell of Fe2O3 and outer shell of Co3O4.

Copper doped hollow structured manganese oxide mesocrystals with controlled phase structure and morphology as anode materials for lithium ion battery with improved electrochemical performance.

We develop a facile synthesis route to prepare Cu doped hollow structured manganese oxide mesocrystals with controlled phase structure and morphology using manganese carbonate as the reactant template. It is shown that Cu dopant is homogeneously distributed among the hollow manganese oxide microspherical samples, and it is embedded in the lattice of manganese oxide by substituting Mn(3+) in the presence of Cu(2+). The crystal structure of manganese oxide products can be modulated to bixbyite Mn2O3 and tetragonal Mn3O4 in the presence of annealing gas of air and nitrogen, respectively. The incorporation of Cu into Mn2O3 and Mn3O4 induces a great microstructure evolution from core-shell structure for pure Mn2O3 and Mn3O4 samples to hollow porous spherical Cu-doped Mn2O3 and Mn3O4 samples with a larger surface area, respectively. The Cu-doped hollow spherical Mn2O3 sample displays a higher specific capacity of 642 mAhg(-1) at a current density of 100 mA g(-1) after 100 cycles, which is about 1.78 times improvement compared to that of 361 mA h g(-1) for the pure Mn2O3 sample, displaying a Coulombic efficiency of up to 99.5%. The great enhancement of the electrochemical lithium storage performance can be attributed to the improvement of the electronic conductivity and lithium diffusivity of electrodes. The present results have verified the ability of Cu doping to improve electrochemical lithium storage performances of manganese oxides.

Carbon-coated Fe-Mn-O composites as promising anode materials for lithium-ion batteries.

Fe-Mn-O composite oxides with various Fe/Mn molar ratios were prepared by a simple coprecipitation method followed by calcining at 600 °C, and carbon-coated oxides were obtained by pyrolyzing pyrrole at 550 °C. The cycling and rate performance of the oxides as anode materials are greatly associated with the Fe/Mn molar ratio. The carbon-coated oxides with a molar ratio of 2:1 exhibit a stable reversible capacity of 651.8 mA h g(-1) at a current density of 100 mA g(-1) after 90 cycles, and the capacities of 567.7, 501.3, 390.7, and 203.8 mA h g(-1) at varied densities of 200, 400, 800, and 1600 mA g(-1), respectively. The electrochemical performance is superior to that of single Fe3O4 or MnO prepared under the same conditions. The enhanced performance could be ascribed to the smaller particle size of Fe-Mn-O than the individuals, the mutual segregation of heterogeneous oxides of Fe3O4 and MnO during delithiation, and heterogeneous elements of Fe and Mn during lithiation.

MoO2-ordered mesoporous carbon hybrids as anode materials with highly improved rate capability and reversible capacity for lithium-ion battery.

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.

Novel magnetic beads based on sodium alginate gel crosslinked by zirconium(IV) and their effective removal for Pb²âº in aqueous solutions by using a batch and continuous systems.

Novel magnetic sodium alginate gel beads (Fe3O4@SA-Zr) were successfully prepared by using zirconium(IV) as crosslinking ions, and used as adsorbent for removal of Pb(2+) ions from aqueous solutions in batch and fixed-bed column systems. Fe3O4@SA-Zr was characterized by SEM, FT-IR, XRD and VSM. Fe3O4@SA-Zr had the macroporous structure, exhibited greater stability and possessed a sensitive magnetic response. More importantly, Fe3O4@SA-Zr exhibited high adsorption capacity, fast kinetics and high selectivity towards Pb(2+) ions. Experimental data was well described by Langmuir isotherm with a maximum adsorption capacity of 333.33 mg/g. FTIR and XPS indicated that the carboxyl and hydroxyl groups of SA and hydroxyl groups binding to Fe and Zr species were involved in Pb(2+) adsorption. Fixed-bed column packed with Fe3O4@SA-Zr exhibited higher removal efficiency for Pb(2+)ions. Consequently, Fe3O4@SA-Zr with excellent absorbability, stability and reusability could be used as a promising adsorbent for Pb(2+) removal in wastewaters.

Preparation and characterization of a novel nano-absorbent based on multi-cyanoguanidine modified magnetic chitosan and its highly effective recovery for Hg(II) in aqueous phase.

A new kind of nano-absorbent with the entirely novel structure, nano-absorbent of multi-cyanogunidine modified magnetic chitosan (CG-MCS nano-absorbent), has been firstly synthesized by using the functionalized chitosan and cross-linking agent with cyanoguanidine group simultaneously. The resulting nano-absorbent was characterized by means of the Fourier transform infrared spectra (FT-IR), transmission electron microscope (TEM), X-ray diffraction (XRD), elemental analysis and vibrating sample magnetometer (VSM). The resulting nano-absorbent basen on multi-cyanoguanidine modified magnetic chitosan has been demonstrated holding highly effective recovery for mercury ions, in other words, it showed both the extraordinary adsorption capacity for Hg(II) at high initial concentration and the strong removal ability for it at low concentration, the maximum adsorption capacity was up to 285 mg g(-1) and the removal percentage could reach 96% at low concentration. Meanwhile, the resulting CG-MCS nano-absorbent also showed a high selectivity adsorption for Hg(II) among coexisting heavy metals and the good regeneration performance.

Enhanced electrochemical performance of FeWO4 by coating nitrogen-doped carbon.

FeWO4 (FWO) nanocrystals were prepared at 180 °C by a simple hydrothermal method, and carbon-coated FWO (FWO/C) was obtained at 550 °C using pyrrole as a carbon source. The FWO/C obtained from the product hydrothermally treated for 5 h exhibits reversible capacities of 771.6, 743.8, 670.6, 532.6, 342.2, and 184.0 mAh g(-1) at the current densities of 100, 200, 400, 800, 1600, and 3200 mA g(-1), respectively, whereas that from the product treated for 0.5 h achieves a reversible capacity of 205.9 mAh g(-1) after cycling 200 times at a current density of 800 mA g(-1). The excellent electrochemical performance of the FWO/C results from the combination of the nanocrystals with good electron transport performance and the nitrogen-doped carbon coating.

Uniform carbon layer coated Mn3O4 nanorod anodes with improved reversible capacity and cyclic stability for lithium ion batteries.

A facile one-step solvothermal reaction route to large-scale synthesis of carbon homogeneously wrapped manganese oxide (Mn(3)O(4)@C) nanocomposites for anode materials of lithium ion batteries was developed using manganese acetate monohydrate and polyvinylpyrrolidone as precursors and reactants. The synthesized Mn(3)O(4)@C nanocomposites were characterized by X-ray diffraction, field-emission scanning electron microscopy, high resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The synthesized tetragonal structured Mn(3)O(4) (space group I41/amd) samples display nanorodlike morphology, with a width of about 200-300 nm and a thickness of about 15-20 nm. It is shown that the carbon layers with a thickness of 5 nm are homogeneously coated on the Mn(3)O(4) nanorods. It is indicated from lithium storage capacity estimation that the Mn(3)O(4)@C samples display enhanced capacity retention on charge/discharge cycling. Even after 50 cycles, the products remains stable capacity of 473 mA h g(-1), which is as much 3.05 times as that of pure Mn(3)O(4) samples. Because of the low-cost, nonpollution, and stable capacity, the carbon homogeneously coated Mn(3)O(4)@C nanocomposites are promising anode material for lithium ion batteries.

Preparation of novel nano-adsorbent based on organic-inorganic hybrid and their adsorption for heavy metals and organic pollutants presented in water environment.

The nanocomposites based on organic-inorganic hybrid have been attracting much attention due to their potential applications used as new type of functional materials, such as colloidal stabilizers, electro-optical devices, and nanocomposites materials. The organic-inorganic hybrid of poly(acrylic acid-acrylonitrile)/attapulgite, P(A-N)/AT nanocomposites, were prepared by using in situ polymerization and composition of acrylic acid (AA) and acrylonitrile (AN) onto modified attapulgite (AT) nanoparticles. The resulting P(A-N)/AT nanocomposites were transformed into novel nano-adsorbent of poly(acrylic acid-acryloamidoxime)/attapulgite by further functionalization, i.e. P(A-O)/AT nano-adsorbent. The adsorption properties of P(A-O)/AT toward metal ions were determined, and the results indicated that the adsorbents with nanocomposite structure held a good of selectivity to Pb(2+) among numerous metal ions. The maximum removal capacity of Pb(2+) was up to 109.9 mg/g and it is notable to see that the adsorption removal of P(A-O)/AT nano-adsorbent for Pb(2+) could achieve more than 96.6% when the initial concentration of Pb(2+) was 120.0 mg/l. The kinetics, isotherm models, and conductivity were introduced to study the adsorption mechanism of P(A-O)/AT for Pb(2+) and it was concluded that it could be chemisorptions process and the best coordination form took place when AO:AA:Pb(2+) = 1:1:1. In addition, after simply treated with CTAB, P(A-O)/AT nano-adsorbent showed better adsorption properties for phenol than the same kinds of materials.

Platinum-nanoparticle-modified TiO2 nanowires with enhanced photocatalytic property.

Highly crystalline Pt nanoparticles with an average diameter of 5 nm were homogeneously modified on the surfaces of TiO(2) nanowires (Pt-TiO(2) NWs) by a simple hydrothermal and chemical reduction route. Photodegradation of methylene blue (MB) in the presence of Pt-TiO(2) NWs indicates that the photocatalytic activity of TiO(2) NWs can be greatly enhanced by Pt nanoparticle modification. The physical chemistry process and photocatalytic mechanism for Pt-TiO(2) NWs hybrids degrading MB were investigated and analyzed. The Pt attached on TiO(2) nanowires induces formation of a Schottky barrier between TiO(2) and Pt naonoparticles, leading to a fast transport of photogenerated electrons to Pt particles. Furthermore, Pt incoporation on TiO(2) surface can accelerate the transfer of electrons to dissolved oxygen molecules. Besides enhancing the electron-hole separation and charge transfer to dissolved oxygen, Pt may also serve as an effective catalyst in the oxidation of MB. However, a high Pt loading value does not mean a high photocatalytic activity. Higher content loaded Pt nanoparticles can absorb more incident photons which do not contribute to the photocatalytic efficiency. The highest photocatalytic activity for the Pt-TiO(2) nanohybrids on MB can be obtained at 1 at % Pt loading.

Large scale synthesis and gas-sensing properties of anatase TiO2 three-dimensional hierarchical nanostructures.

Three-dimensional (3D) crystalline anatase titanium dioxide (TiO(2)) hierarchical nanostructures were synthesized through a facile and controlled hydrothermal and after-annealing process. The formation mechanism for the anatase TiO(2) 3D hierarchical nanostructures was investigated in detail. The 3D hierarchical nanostructures morphologies are formed by self-organization of several tens of radially distributed thin petals with a thickness of several nanometers with a larger surface area. The surface area of TiO(2) hierarchical nanostructures determined by the Brunauer-Emmett-Teller (BET) adsorption isotherms was measured to be 64.8 m(2) g(-1). Gas sensing properties based on the hierarchical nanostructures were investigated. A systematic study on sensitivity as a function of temperatures and gas concentrations was carried out. It reveals an improved ethanol gas sensing response property with a sensitivity of about 6.4 at 350 degrees C upon exposure to 100 ppm ethanol vapor for the TiO(2) hierarchical nanostructures. A gas sensing mechanism based on the adsorption-desorption of oxygen on the surface of TiO(2) is discussed and analyzed. This novel gas sensor can be multifunctional and promising for practical applications. Furthermore, the hierarchical nanostructures with high surface area can find variety of potential applications such as solar cells, biosensors, catalysts, etc.

Sol-gel growth of hexagonal faceted ZnO prism quantum dots with polar surfaces for enhanced photocatalytic activity.

The hexagonal faceted ZnO quantum dots (QDs) about 3-4 nm have been prepared via a sol-gel route by using oleic acid (OA) as the capping agent. It is revealed by electron diffraction patterns and high resolution transmission electron microscopy lattice images that the profile surfaces of the highly crystalline ZnO QDs are mainly composed of {100} planes, with the Zn-terminated (001) faces and the opposite (001) faces presented as polar planes. Compared with spherical ZnO QDs, the hexagonal faceted ZnO QDs show enhanced photocatalytic activity for photocatalytic decomposition of methylene blue. A mechanism for the enhanced photocatalytic activity of the hexagonal faceted ZnO QDs for degradation of methylene blue is proposed. In addition to the large specific surface areas due to small size and high crystalline, the enhanced photocatalytic activity can mainly be ascribed to the special hexagonal morphology. The Zn-terminated (001) and O-terminated (001) polar faces are facile to adsorb oxygen molecules and OH(-) ions, resulting in a greater production rate of H(2)O(2) and OH(*) radicals, hence promoting the photocatalysis reaction. The synthesized hexagonal-shaped ZnO QDs with high photocatalytic efficiency will find widespread potential applications in environmental and biological fields.

ZnO nanostructure construction on zinc foil: the concept from an ionic liquid precursor aqueous solution.

Aligned ZnO arrays with branched rods, hexagonal rods, quasi-round rods, hexagonal pyramids and porous nanostructures are constructed on zinc foil in the ionic liquid tetrabutylammonium hydroxide aqueous solution.

Low temperature induced synthesis of TiN nanocrystals.

TiN nanocrystals were successfully prepared through the direct reaction between TiCl(4) and NaNH(2) induced at 300 degrees C. The yield based on Ti is approximately 80%. X-ray powder diffraction indicated that the product was cubic TiN with a lattice constant of a = 4.243 A. Transmission electron microscopy revealed that nanocrystalline TiN with a diameter of 10 nm or so and extremely long straight rods were synthesized. The possible formation mechanism was also proposed.