Yong Wang

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Name: 王勇; Yong Wang

Organization: Shanghai University

Department: Department of Chemical Engineering

Title: Professor

TOPICS

Material Chemistry

Carbon Nanotubes Graphene & Graphite

Inorganic Chemistry

Metal Organic Frameworks Mesoporous Material

Chemicals
References

Conversion of Bulk Metallurgical Silicon into Photocatalytic Nanoparticles by Copper-Assisted Chemical Etching

Co-reporter:Yu Sun;Si Chen;Xiaopeng Li;Baoqin Guan;Junna Wang;Stefan Schweizer;Ralf B. Wehrspohn

ACS Sustainable Chemistry & Engineering December 5, 2016 Volume 4(Issue 12) pp:6590-6599

Publication Date(Web):September 29, 2016

DOI:10.1021/acssuschemeng.6b01481

Low-grade metallurgical silicon (MG-Si, purity ∼98%–99%, $1/kg) with annual production over six million tons is an attractive feedstock to produce active photocatalysts. However, MG-Si is known as an electronically dead material due to serious charge recombination associated with high metal impurity levels. Upgrading MG-Si close to solar grade is essential to achieve desired performance; nevertheless, the traditional silicon refinement process is cost ineffective, has high energy consumption, and causes environmental pollution. Here, we address this critical issue by employing a room-temperature one-step Cu-assisted chemical etching (CuACE) process, which successfully purifies MG-Si into active photocatalysts. We discover that the use of reducing agent (H3PO3) instead of commonly employed oxidant (H2O2) in the etchant system induces a novel phenomenon called “chemical cracking effect”. This effect significantly decreases the granularity of bulk MG-Si particles and simultaneously exposes fresh surfaces carrying impurities to the acids. This induces CuACE with promising purification rates, where major removal efficiencies of metal impurity reach 98.2% for Fe, 62.6% for Ca, and 61.0% for Al. Also, purified MG-Si exhibits excellent photocatalytic activity toward methyl orange (MO) degradation. Our approach provides new insights into metal-assisted chemical etching (MACE) of dirty silicon and opens a path for utilization of MG-Si in heterogeneous photocatalysis.Keywords: Metal-assisted chemical etching (MACE); Metallurgical silicon; Photocatalytic degradation; Purification; Silicon nanoparticles;

MOF-derived yolk–shell CdS microcubes with enhanced visible-light photocatalytic activity and stability for hydrogen evolution

Co-reporter:Yun Su;Dan Ao;Hong Liu

Journal of Materials Chemistry A 2017 vol. 5(Issue 18) pp:8680-8689

Publication Date(Web):2017/05/10

DOI:10.1039/C7TA00855D

Yolk–shell structures with a unique three-dimensional (3D) open architecture offer great advantages for constructing advanced photocatalysts. However, metal sulfides with yolk–shell nanostructures were rarely reported. In this work, unique yolk–shell CdS microcubes are synthesized from Cd–Fe Prussian blue analogues (Cd–Fe-PBA) through a facile microwave-assisted hydrothermal process. Their formation mechanism is also proposed based on the anion exchange and Kirkendall effect process. Benefitting from structural merits, including a 3D open structure, small size of primary nanoparticles, high specific surface area, and good structural robustness, the obtained yolk–shell CdS microcubes manifest excellent performances for photocatalytic hydrogen evolution from H2O under visible-light irradiation. The photocatalytic H2 evolution rate is 3051.4 μmol h−1 g−1 (with an apparent quantum efficiency of 4.9% at 420 nm), which is ∼2.43 times higher than that of conventional CdS nanoparticles. Furthermore, the yolk–shell CdS microcubes exhibit remarkable photocatalytic stability. This work demonstrates that MOF-derived yolk–shell structured materials hold great promise for application in the field of energy conversion.

Cd0.2Zn0.8S@UiO-66-NH2 nanocomposites as efficient and stable visible-light-driven photocatalyst for H2 evolution and CO2 reduction

Co-reporter:Yun Su, Zhe Zhang, Hong Liu, Yong Wang

Applied Catalysis B: Environmental 2017 Volume 200(Volume 200) pp:

Publication Date(Web):1 January 2017

DOI:10.1016/j.apcatb.2016.07.032

•Cd0.2Zn0.8S@UiO-66-NH2 nanocomposites were synthesized by a solvothermal method.•The obtained composites exhibited excellent photocatalytic activity and stability.•A H2 production rate of 5846.5 μmol h−1 g−1 was obtained over the optimal catalyst.•The optimal catalyst also showed a CH3OH production rate of 6.8 μmol h−1 g−1.•An efficient charge separation and transfer was observed in the composites.Metal-organic frameworks (MOFs), a new class of porous crystalline materials, have attracted great interest as fascinating materials for sustainable energy and environmental remediation. However, the functionalization and diversification of MOFs are still challenging and imperative for the development of highly active MOF-based materials. In this study, a series of Cd0.2Zn0.8S@UiO-66-NH2 nanocomposites with different UiO-66-NH2 contents were fabricated via a facile solvothermal method. The photocatalytic performances of the obtained Cd0.2Zn0.8S@UiO-66-NH2 nanocomposites were evaluated by photocatalytic H2 evolution and CO2 reduction under visible-light irradiation. The resultant hybrids exhibit significantly enhanced photocatalytic activity for hydrogen evolution and CO2 reduction as compared with pristine components, and the optimal UiO-66-NH2 content is 20 wt%. The composite can show a hydrogen evolution rate of 5846.5 μmol h−1 g−1 and a CH3OH production rate of 6.8 μmol h−1 g−1. The remarkable enhancement of the photocatalytic activity should be attributed to the efficient charge separation and transfer on the interface between Cd0.2Zn0.8S and UiO-66-NH2. Furthermore, the Cd0.2Zn0.8S@UiO-66-NH2 photocatalysts show excellent stability during photocatalytic hydrogen evolution and CO2 reduction. This work demonstrates that MOF-based composite materials hold great promise for applications in the field of energy conversion and environmental purification.Download high-res image (143KB)Download full-size image

Metal-organic frameworks derived germanium oxide nanosheets for large reversible Li-ion storage

Co-reporter:Wenbo Zhang, Huicong Pang, Weiwei Sun, Li-Ping Lv, Yong Wang

Electrochemistry Communications 2017 Volume 84(Volume 84) pp:

Publication Date(Web):1 November 2017

DOI:10.1016/j.elecom.2017.09.019

•The GeO2 nanosheet is investigated as the Li-battery electrode for the first time.•Ge-organic framework is used as the precursor.•The GeO2 nanosheet shows large Li-storage capacity and very long cycle life.A Ge-based metal-organic framework (MOF) precursor [C6H10(NH2)2Ge3O6] is used to fabricate two-dimensional GeO2 nanosheets in this work. The obtained micrometer-sized GeO2 nanosheet delivers superior lithium-storage capability during long cycling (an initial reversible capacity of 1315 mAh g− 1 at 100 mA g− 1 and the retained capacity of 1393 mAh g− 1 after 350 cycles). The observed large capacity and good cyclability have been mainly attributed to its nanosheet structure inherited from the MOF precursor, which can facilitate the electrolyte infusion and the lithium diffusion, maintain the structural stability, and alleviate the large volume change of the electrode during repetitive lithiation/delithiation process.Download high-res image (214KB)Download full-size image

Efficient Activation of High-Loading Sulfur by Small CNTs Confined Inside a Large CNT for High-Capacity and High-Rate Lithium–Sulfur Batteries

Co-reporter:Feiying Jin, Suo Xiao, Lijie Lu, and Yong Wang

Nano Letters 2016 Volume 16(Issue 1) pp:440-447

Publication Date(Web):December 16, 2015

DOI:10.1021/acs.nanolett.5b04105

Sulfur with a high specific capacity of 1673 mAh g–1 is yet to be used as commercial cathode for lithium batteries because of its low utilization rate and poor cycle stability. In this work, a tube-in-tube carbon structure is demonstrated to relieve the critical problems with sulfur cathode: poor electrical conductivity, dissolution of lithium polysulfides, and large volume change during cycling. A number of small carbon nanotubes (∼20 nm in diameter) and a high loading amount of 85.2 wt % sulfur are both filled completely inside a large amorphous carbon nanotube (∼200 nm in diameter). Owing to the presence of these electrically conductive, highly flexible and structurally robust small CNTs and a large CNT overlayer, sulfur material exhibits a high utilization rate and delivers a large discharge capacity of 1633 mAh g–1 (based on the mass of sulfur) at 0.1 C, approaching its theoretical capacity (1673 mAh g–1). The obtained S-CNTs@CNT electrode demonstrates superior high-rate cycling performances. Large discharge capacities of ∼1146, 1121, and 954 mAh g–1 are observed after 150 cycles at large current rates of 1, 2, and 5 C, respectively.

BimetalOrganic Framework: One-Step Homogenous Formation and its Derived Mesoporous Ternary Metal Oxide Nanorod for High-Capacity, High-Rate, and Long-Cycle-Life Lithium Storage

Co-reporter:Hao Li;Ming Liang;Weiwei Sun

Advanced Functional Materials 2016 Volume 26( Issue 7) pp:1098-1103

Publication Date(Web):

DOI:10.1002/adfm.201504312

Metal–organic frameworks (MOFs) and relative structures with uniform micro/mesoporous structures have shown important applications in various fields. This paper reports the synthesis of unprecedented mesoporous Ni_xCo_3−xO₄ nanorods with tuned composition from the Co/Ni bimetallic MOF precursor. The Co/Ni-MOFs are prepared by a one-step facile microwave-assisted solvothermal method rather than surface metallic cation exchange on the preformed one-metal MOF template, therefore displaying very uniform distribution of two species and high structural integrity. The obtained mesoporous Ni_0.3Co_2.7O₄ nanorod delivers a larger-than-theoretical reversible capacity of 1410 mAh g⁻¹ after 200 repetitive cycles at a small current of 100 mA g⁻¹ with an excellent high-rate capability for lithium-ion batteries. Large reversible capacities of 812 and 656 mAh g⁻¹ can also be retained after 500 cycles at large currents of 2 and 5 A g⁻¹, respectively. These outstanding electrochemical performances of the ternary metal oxide have been mainly attributed to its interconnected nanoparticle-integrated mesoporous nanorod structure and the synergistic effect of two active metal oxide components.

Ultrasmall Tin Nanodots Embedded in Nitrogen-Doped Mesoporous Carbon: Metal-Organic-Framework Derivation and Electrochemical Application as Highly Stable Anode for Lithium Ion Batteries

Co-reporter:Ruoling Dai, Weiwei Sun, Yong Wang

Electrochimica Acta 2016 Volume 217() pp:123-131

Publication Date(Web):1 November 2016

DOI:10.1016/j.electacta.2016.08.051

•Sn-based metal-organic-framework (MOF) is prepared.•Ultrasmall tin nanodots (2–3 nm) are embedded in nitrogen-doped mesoporous carbon.•The Sn/C composite anode shows high capacity and ultralong cycle life.This work reports a facile metal-organic-framework based approach to synthesize Sn/C composite, in which ultrasmall Sn nanodots with typical size of 2–3 nm are uniformly embedded in the nitrogen-doped porous carbon matrix (denoted as Sn@NPC). The effect of thermal treatment and nitrogen doping are also explored. Owing to the delicate size control and confined volume change within carbon matrix, the Sn@NPC composite can exhibit reversible capacities of 575 mAh g−1 (Sn contribution: 1091 mAh g−1) after 500 cycles at 0.2 A g−1 and 507 mAh g−1 (Sn contribution: 1077 mAh g−1) after 1500 cycles at 1 A g−1. The excellent long-life electrochemical stability of the Sn@NPC anode has been mainly attributed to the uniform distribution of ultrasmall Sn nanodots and the highly-conductive and flexible N-doped carbon matrix, which can effectively facilitate lithium ion/electron diffusion, buffer the large volume change and improve the structure stability of the electrode during repetitive cycling with lithium ions.The Sn@NPC composite with ultrasmall Sn nanodots embedded in the nitrogen-doped mesoporous carbon is synthesized by a MOF-based approach and delivers good Li-storage properties.

Metal-Organic-Frameworks Derivation of Mesoporous NiO Nanorod for High-Performance Lithium Ion Batteries

Co-reporter:Huicong Pang, Baoqin Guan, Weiwei Sun, Yong Wang

Electrochimica Acta 2016 Volume 213() pp:351-357

Publication Date(Web):20 September 2016

DOI:10.1016/j.electacta.2016.06.163

Metal-organic-frameworks (MOF) derivation has been demonstrated to be an effective strategy to obtain porous metal oxides with controlled morphologies and improved electrochemical properties for lithium-ion batteries. One-dimensional mesoporous NiO nanorod is synthesized for the first time in this work from a rod-like Ni-MOF precursor, which is formed by a fast and facile room-temperature reaction. The mesoporous NiO nanorod delivers a larger-than-theoretical reversible capacity of 1019 mAh g−1 after 100 cycles at 100 mA g−1 and good high-rate capabilities when used as an anode material for rechargeable lithium ion batteries. The mesoporous structure derived from the MOF precursor along with 1D nanoparticle-integrated nanorod morphology can facilitate lithium diffusion, resist volume change and maintain structural stability of the electrode during repetitive cycling, thus resulting in enhanced reversible Li-storage capacities and excellent cyclability.The mesoporous NiO nanorod, synthesized for the first time from a MOF precursor, achieves a reversible larger-than-theoretical capacity of 1019 mAh g−1 after 100 cycles when used as an anode for lithium ion batteries.

Plasmonic Ag coated BiOBr0.2I0.8 nanosheets grown on graphene with excellent visible-light photocatalytic activity

Co-reporter:Hong Liu, Zhen Chen, Yong Wang

Journal of Photochemistry and Photobiology A: Chemistry 2016 Volume 326() pp:30-40

Publication Date(Web):15 July 2016

DOI:10.1016/j.jphotochem.2016.04.016

•Ag coated BiOBr0.2I0.8 nanosheet/graphene sheet-on-sheet composites were synthesized.•The obtained ternary composites exhibited excellent photocatalytic activity.•A synergistic effect between the three components of the composites was observed.•Both the h+ and OH were the active species in the degradation process.A series of visible light-responsive plasmonic Ag coated BiOBr0.2I0.8 nanosheets are grown on graphene by a combined solvothermal and photodeposition method. The ternary Ag/BiOBr0.2I0.8/graphene nanocomposites exhibit significantly enhanced photocatalytic activity than pristine BiOBr0.2I0.8 and the binary BiOBr0.2I0.8/graphene composite. When the loading amount of Ag is 1.0 wt%, the Ag/BiOBr0.2I0.8/graphene nanocomposite displays the highest photocatalytic activity. The rate constants for the ternary Ag/BiOBr0.2I0.8/graphene composite to degrade rhodamine B (RhB) and methylene blue (MB) are determined to be ∼5.28 and 5.57 times as large as those of pristine BiOBr0.2I0.8, respectively. The high photocatalytic activity is attributed predominantly to the hybridization of the surface plasmonic resonance (SPR) effect of Ag nanoparticles and the specific electronics effect of graphene, thus enhancing the separation of photogenerated charge carriers of BiOBr0.2I0.8. Meanwhile, the excellent adsorption capacity of graphene and the broad absorption in the visible light region also contribute to the enhancement of photocatalytic activity. Both the holes and hydroxyl radicals were the active species in the degradation process.

Standing carbon-coated molybdenum dioxide nanosheets on graphene: morphology evolution and lithium ion storage properties

Co-reporter:Lei Guo and Yong Wang

Journal of Materials Chemistry A 2015 vol. 3(Issue 8) pp:4706-4715

Publication Date(Web):08 Jan 2015

DOI:10.1039/C4TA05520A

Transitional metal oxides are a class of high-capacity anodes for lithium ion batteries. Drastic volume changes during cycling and intrinsically poor electronic conductivity diminish their electrochemical performances such as cycliability and high-rate capabilities. This study reports an unprecedented MoO2/carbon network, consisting of the standing carbon-coated MoO2 nanosheets on graphene nanosheets to solve these problems. The obtained MoO2 products can be tuned to have particle-like, rod-like, or sheet-like morphologies (standing MoO2@C core–shell nanosheets or flat-lying MoO2 nanosheets) on graphene by adjusting the experimental parameters. Due to the unique three dimensional porous MoO2@C/graphene hierarchical structure, the composite manifests excellent electrochemical properties including high capacity, long cycle life and stable high-rate performances. A large reversible capacity of above 500 mA h g−1 can be achieved after 200 cycles at a large current of 5 A g−1.

New Cr2Mo3O12-based anodes: morphology tuning and Li-storage properties

Co-reporter:Lei Guo and Yong Wang

Journal of Materials Chemistry A 2015 vol. 3(Issue 29) pp:15030-15038

Publication Date(Web):21 May 2015

DOI:10.1039/C5TA03256C

A new ternary metal oxide (Cr2Mo3O12) anode for Li-ion batteries is reported in this work. Experimental conditions such as reaction temperature, reaction time, and reactant concentration have all been investigated. The product can be obtained with sheet-like or rod-like morphology with/without the presence of a graphene support. The Cr2Mo3O12/graphene rod-on-sheet composite is found to be more suitable for Li-storage compared to the Cr2Mo3O12/graphene sheet-on-sheet composite and pristine Cr2Mo3O12 nanosheets/nanorods. The rod-on-sheet composite delivers a large reversible capacity of 988 mA h g−1 after 50 cycles at a current density of 100 mA g−1 and a good rate capability. Moreover, a preliminary Li-storage mechanism is also explored and suggested.

Topotactical conversion of carbon coated Fe-based electrodes on graphene aerogels for lithium ion storage

Co-reporter:Feiying Jin and Yong Wang

Journal of Materials Chemistry A 2015 vol. 3(Issue 28) pp:14741-14749

Publication Date(Web):08 Jun 2015

DOI:10.1039/C5TA03605D

Iron oxides and iron sulfides have attracted significant research concerns for lithium-ion batteries (LIBs) due to their higher theoretical capacity than the commercial electrode. However, they both suffer from large volume expansion during cycling and poor electrical conductivity. Iron sulfides have another problem of the dissolution of polysulfides into organic electrolytes. This work reports a sulfur-doped graphene aerogel (GA) supported FeS2@carbon composite with better lithium ion storage properties than its intermediate precursors (GA supported Fe–Fe3O4@C and Fe2O3). It exhibits a high reversible capacity of ∼1000 mA h g−1 at 0.1 C during cycling with good rate capability. These enhanced electrochemical properties are mainly attributed to the synergetic effect of the GA support, carbon coating and sulfur doping.

Polyurethane-derived N-doped porous carbon with interconnected sheet-like structure as polysulfide reservoir for lithium–sulfur batteries

Co-reporter:Suo Xiao, Songhang Liu, Jianqiu Zhang, Yong Wang

Journal of Power Sources 2015 Volume 293() pp:119-126

Publication Date(Web):20 October 2015

DOI:10.1016/j.jpowsour.2015.05.048

•N-doped porous carbon with interconnected sheet-like structure is prepared.•Polyurethane foam waste is used as the precursor in the thermal activation process.•The carbon–sulfur composite shows good cycling performances for Li–S batteries.Environmental pollution and energy deficiency are two key issues for the sustainable development of the modern society. Polyurethane foam is a typical commercial polymer with a large production quantity and its waste needs to be recycled. Lithium–sulfur battery is a promising energy-storage device with high energy density and low cost, but its demerits such as poor conductivity of the sulfur and severe capacity degradation due to the soluble lithium polysulfides are still a big challenge. This work reports a facile method to prepare nitrogen-doped porous carbon (NPC) from the polyurethane foam (PUF) waste and use it as a reservoir to impregnate sulfur for lithium–sulfur batteries. The obtained NPC has a unique interconnected sheet-like porous morphology with a large surface area of 1315 m2 g−1. The NPC-S composite delivers a large reversible capacity of 1118 mAh g−1 with good cycling performances and excellent high-rate capabilities. A large reversible capacity of 460 mAh g−1 can be retained at a large current of 5C (8.35 A g−1) after 100 cycles.

Microwave Hydrothermal Synthesis of Ni-based Metal–Organic Frameworks and Their Derived Yolk–Shell NiO for Li-Ion Storage and Supported Ammonia Borane for Hydrogen Desorption

Co-reporter:Shaofeng Kong, Ruoling Dai, Hao Li, Weiwei Sun, and Yong Wang

ACS Sustainable Chemistry & Engineering 2015 Volume 3(Issue 8) pp:1830

Publication Date(Web):July 6, 2015

DOI:10.1021/acssuschemeng.5b00556

This paper reports fast microwave hydrothermal synthesis of Ni-based metal–organic frameworks (Ni-MOFs) and their derived yolk–shell NiO structures by direct calcination in air. The molar ratio of the Ni ion to the benzene-1,3,5-tricarboxylic acid (H3BTC) ligand has important influence on the NiO morphologies and their electrochemical performances. The obtained yolk–shell NiO microsphere displays a large reversible capacity of 1060 mAh g–1 at a small current density of 0.2 A g–1 and a good high-rate capability when evaluated as an anode for rechargeable lithium-ion batteries. Moreover, the facilitated hydrogen release from ammonia borane (AB) at a lower temperature and the depressed release of undesired volatile byproducts are also observed in the Ni-MOFs supported AB.Keywords: Hydrogen desorption; Lithium-ion battery; Metal−organic frameworks; NiO; Yolk−shell

Graphene-supported nickel chloride and cobalt chloride nanoparticles as highly efficient catalysts for dehydrogenation of ammonia borane

Co-reporter:Weiwei Sun, Hao Li, Yong Wang

International Journal of Hydrogen Energy 2015 Volume 40(Issue 45) pp:15389-15397

Publication Date(Web):7 December 2015

DOI:10.1016/j.ijhydene.2015.09.088

•NiCl2/CoCl2-GNS composites are synthesized and used for loading AB.•AB@NiCl2/CoCl2-GNS exhibits lower dehydrogenation temperature.•The by-products are completely suppressed for AB@NiCl2/CoCl2-GNS.•The activation energy of AB decomposition is effectively reduced.This work reports the synthesis of a new matrix material (graphene-supported NiCl2 and CoCl2 nanoparticles) for loading ammonia borane (AB) and investigates their catalysis effect for dehydrogenation properties. The NiCl2 and CoCl2 nanoparticles are obtained with the size around 3–10 nm and dispersed uniformly on the surface of graphene, which exhibit enhanced catalysis effect for the dehydrogenation of AB. The AB@NiCl2/CoCl2-graphene system, obtained via loading AB on the NiCl2/CoCl2-graphene scaffold, shows much lower onset dehydrogenation temperature of 60–90 °C and effective suppression of those byproducts such as ammonia, diborane and borazine formations compared with pristine AB. Meanwhile, the activation energy of AB@NiCl2/CoCl2-graphene has been calculated to explore the improvement of dehydrogenation kinetics of AB under the existence of graphene-supported NiCl2 or CoCl2 nanoparticles.Graphene-supported NiCl2 and CoCl2 nanoparticles are successfully synthesized and used for loading ammonia borane (AB). The composites achieve significantly improved hydrogen release temperatures and effective suppression of those byproducts such as ammonia, diborane and borazine during decomposition of AB.

Visible light-driven Bi2Sn2O7/reduced graphene oxide nanocomposite for efficient photocatalytic degradation of organic contaminants

Co-reporter:Hong Liu, Zhitong Jin, Yun Su, Yong Wang

Separation and Purification Technology 2015 Volume 142() pp:25-32

Publication Date(Web):4 March 2015

DOI:10.1016/j.seppur.2014.12.027

•Bi2Sn2O7/RGO composite were synthesized by a hydrothermal method.•Enhanced visible light absorption was observed in Bi2Sn2O7/RGO composite.•RGO acted as an electron-acceptor to hinder the charge recombination.•The resulting composite exhibited high visible light photocatalytic activity.In this work, a novel Bi2Sn2O7/reduced graphene oxide (RGO) nanocomposite was synthesized by a one-step hydrothermal method. The prepared composite was characterized by means of powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrometry (EDS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) emission spectroscopy and electrochemical impedance spectroscopy (EIS). The photocatalytic activity of the Bi2Sn2O7/RGO composite was investigated by the degradation of rhodamine B (RhB) and phenol. An increase in photocatalytic activity was observed for Bi2Sn2O7/RGO composite compared with pure Bi2Sn2O7 under visible light. The enhanced photocatalytic performance of the composite was mainly ascribed to the more effective charge separations and the excellent adsorption capacity of RGO. The composite maintained its ability to degrade pollutants efficiently, even after 4 cycles of photocatalysis. Further study proved that both the holes and hydroxyl radicals were the active species in the degradation process.

Multilayer CuO@NiO Hollow Spheres: Microwave-Assisted Metal–Organic-Framework Derivation and Highly Reversible Structure-Matched Stepwise Lithium Storage

Co-reporter:Wenxiang Guo, Weiwei Sun, and Yong Wang

ACS Nano 2015 Volume 9(Issue 11) pp:11462

Publication Date(Web):October 7, 2015

DOI:10.1021/acsnano.5b05610

A unique CuO@NiO microsphere with three-layer ball-in-ball hollow morphology is successfully synthesized by Cu–Ni bimetallic organic frameworks. The beforehand facile microwave-assisted production of the Ni organic framework sphere is used as the template to induce the morphology control of bimetallic oxides. Designed by the controlled surface cationic exchange reactions between Cu and Ni ions, there is an elemental gradient (decreased amount of CuO but increased amount of NiO) from the shell to the core of the microsphere product. This ternary metal oxide hollow structure is found to be very suitable for solving the critical volume expansion problem, which is critical for all high-capacity metal oxide electrodes for lithium ion batteries. A reversible larger-than-theoretical capacity of 1061 mAh·g–1 can be retained after a repetitive 200 cycles without capacity fading compared to the initial cycle. These excellent electrochemical properties are ascribed to the step-by-step lithium insertion reactions induced by the matched CuO@NiO composition from the shell to the core and facilitated lithium/electron diffusion and accommodated volume change in the porous bimetallic oxides microsphere with a multiple-layer yolk–shell nanostructure.Keywords: ball-in-ball; CuO; hollow sphere; lithium-ion battery; metal organic framework; NiO;

NiS nanorod-assembled nanoflowers grown on graphene: morphology evolution and Li-ion storage applications

Co-reporter:Hua Geng, Shao Feng Kong and Yong Wang

Journal of Materials Chemistry A 2014 vol. 2(Issue 36) pp:15152-15158

Publication Date(Web):17 Jul 2014

DOI:10.1039/C4TA03440F

This paper reports the morphology, size and phase control of NiS nanoflowers on a graphene substrate. The growth mechanisms of various building blocks for NiS nanoflowers such as nanosheets, nanoflakes, and nanorods are explored under varied experimental conditions. All the obtained NiS nanoflowers were found to be uniformly dispersed on graphene nanosheets, forming a sandwiched nanostructure. When fabricated as an anode material for Li-ion batteries, the graphene supported NiS nanorod-assembled nanoflower shows better cycling performances than pristine NiS and other NiS–graphene composites. It shows a large unprecedented reversible lithium-extraction capacity of 887 mA h g−1 after 60 cycles at 59 mA g−1 and good high-rate capability among NiS-based anodes.

A reduced graphene oxide supported Cu3SnS4 composite as an efficient visible-light photocatalyst

Co-reporter:Hong Liu, Zhen Chen, Zhitong Jin, Yun Su and Yong Wang

Dalton Transactions 2014 vol. 43(Issue 20) pp:7491-7498

Publication Date(Web):20 Mar 2014

DOI:10.1039/C4DT00070F

In this study, a visible light responsive Cu3SnS4/reduced graphene oxide (RGO) photocatalyst has been synthesized by a facile one-step solvothermal method. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, N2 adsorption–desorption, UV–vis diffuse reflectance spectra (DRS), and photoluminescence (PL) emission spectroscopy. The photocatalytic activity of the Cu3SnS4/RGO composite under visible-light irradiation (λ > 420 nm) was evaluated by measuring the degradation of rhodamine B (RhB) and phenol. The results revealed that the Cu3SnS4 nanoplates dispersed uniformly on the RGO surface. The Cu3SnS4/RGO composite exhibited much higher photocatalytic activity than pure Cu3SnS4. The enhancement in photocatalytic activity is likely to be due to the synergistic effect of an improved adsorptivity of pollutants, an enhanced visible light absorption and an effective charge separation. In addition, the Cu3SnS4/RGO photocatalyst was stable during the reaction and could be used repeatedly.

Novel 3D flowerlike Au/BiOBr0.2I0.8 composites with highly enhanced visible-light photocatalytic performances

Co-reporter:Hong Liu, Yun Su, Zhen Chen, Zhitong Jin, Yong Wang

Separation and Purification Technology 2014 Volume 133() pp:343-350

Publication Date(Web):8 September 2014

DOI:10.1016/j.seppur.2014.07.020

•Novel 3D flowerlike Au/BiOBr0.2I0.8 composites were synthesized.•Enhanced visible-light absorption was observed in Au/BiOBr0.2I0.8.•Au nanoparticles could act as electron traps to promote the electron–hole separation.•The Au/BiOBr0.2I0.8 composites exhibited high visible-light photocatalytic activity.A series of 3D flowerlike Au/BiOBr0.2I0.8 composites with different Au contents have been synthesized by a hydrothermal combinated with photodeposition method. The as-prepared samples were characterized by power X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution transmission electron micrographs (HRTEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS), and photoluminescence (PL) emission spectroscopy. The photocatalytic activities of these Au/BiOBr0.2I0.8 composites under visible-light irradiation (λ > 420 nm) were evaluated by the degradation of methyl orange (MO), rhodamine B (RhB) and phenol. The results revealed that the Au/BiOBr0.2I0.8 composites exhibited much higher photocatalytic activities than pure BiOBr0.2I0.8. And the 0.6%Au/BiOBr0.2I0.8 sample exhibited the highest photocatalytic activity. The enhanced photocatalytic activity could be attributed to Au deposits by acting as electron traps and the surface plasma resonance effect of Au. A possible photocatalytic mechanism of Au/BiOBr0.2I0.8 composites was also proposed.Graphical abstract

Microwave hydrothermal growth of In2S3 interconnected nanoflowers and nanoparticles on graphene for high-performance Li-ion batteries

Co-reporter:Yan Gu and Yong Wang

RSC Advances 2014 vol. 4(Issue 17) pp:8582-8589

Publication Date(Web):16 Jan 2014

DOI:10.1039/C3RA46514D

This paper reports microwave-assisted fast hydrothermal synthesis of In2S3 nanoparticles and unprecedented interconnected nanoflowers on graphene surface. The growth mechanisms for various In2S3-based products are investigated. These obtained In2S3 nanoparticles and nanoflowers are found to be uniformly dispersed on graphene nanosheets, forming sandwiched particle-on-sheet and unprecedented flower-on-sheet nanostructures. When fabricated as anode materials, In2S3–graphene composites show extraordinary large reversible capacities and good cycling performances and high rate capabilities. A reversible initial lithium-extraction capacity of 1249 mA h g−1 is observed for the novel In2S3–graphene flower-on-sheet nanostructure at 70 mA g−1, which can be retained at 913, 782, 690 mA h g−1 at large currents of 700, 1400, 3500 mA g−1 respectively. In comparison, the In2S3–graphene nanoparticle-on-sheet composite shows slightly lower reversible capacities but more stable cycling performances at both small and high currents mainly due to the presence of more graphene.

Four-Layer TinCarbon Nanotube YolkShell Materials for High-Performance Lithium-Ion Batteries

Co-reporter:Peng Chen;Fengdan Wu ;Dr. Yong Wang

ChemSusChem 2014 Volume 7( Issue 5) pp:1407-1414

Publication Date(Web):

DOI:10.1002/cssc.201301198

Abstract

All high-capacity anodes for lithium-ion (Li-ion) batteries, such as those based on tin (Sn) and silicon (Si), suffer from large volume changes during cycling with lithium ions, and their high capacities can be only achieved in the first few cycles. We design and synthesize a unique four-layer yolk–shell tin–carbon (Sn–C) nanotube array to address this problem. The shape and size of the exterior Sn nanotube@carbon core–shell layer, the encapsulated interior Sn nanowire@carbon nanotube core–shell layer, and the filling level of each layer can be all controlled by adjusting the experimental conditions. Such a nanostructure has not been reported for any metal or metal oxide-based material. Owing to the special design of the electrode structure, the four-layer hierarchical structure demonstrates excellent Li-ion storage properties in terms of high capacity, long cycle life, and high rate performance.

Morphological Effect of Graphene Nanosheets on Ultrathin CoS Nanosheets and Their Applications for High-Performance Li-Ion Batteries and Photocatalysis

Co-reporter:Shaofeng Kong ; Zhitong Jin ; Hong Liu

The Journal of Physical Chemistry C 2014 Volume 118(Issue 44) pp:25355-25364

Publication Date(Web):October 17, 2014

DOI:10.1021/jp508698q

A unique CoS-graphene sheet-on-sheet nanocomposite has been successfully prepared by anchoring CoS nanosheets on the surface of graphene nanosheets (GNS) with the assistance of the structure-directing agent of ethylenediamine. The shape and size of the introduced CoS nanosheets can be further adjusted by varying the amount of GNS. The unprecedented sheet-like CoS structure is believed to be matched well with GNS basically due to their similar two-dimensional structure with maximum contact areas between two components. The strong interaction between CoS and the underlying highly conductive graphene can facilitate fast electron and ion transport and improve structure stability of the composite. The composite with 26.2% GNS displays excellent electrochemical performance when evaluated as an anode for rechargeable lithium-ion battery. A larger-than-theoretical reversible capacity of 898 mAh/g can be delivered after 80 cycles at 0.1 C along with excellent high-rate cycling performance. The CoS-graphene sheet-on-sheet composite is also used for the first time as a photocatalyst with promising properties for the degradation of methylene blue.

Bi7O9I3/reduced graphene oxide composite as an efficient visible-light-driven photocatalyst for degradation of organic contaminants

Co-reporter:Hong Liu, Yun Su, Zhen Chen, Zhitong Jin, Yong Wang

Journal of Molecular Catalysis A: Chemical 2014 Volume 391() pp:175-182

Publication Date(Web):September 2014

DOI:10.1016/j.molcata.2014.04.029

•Bi7O9I3/RGO composite were synthesized by a solvothermal method.•Enhanced visible light absorption was observed in Bi7O9I/RGO composite.•RGO acted as an electron-acceptor to hinder the charge recombination.•The resulting composite exhibited high visible light photocatalytic activity.Bi7O9I3/reduced graphene oxide (RGO) composite with visible light response was fabricated by a facile solvothermal method. The prepared samples were characterized by means of powder X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), Raman spectra, X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS), and photoluminescence (PL) emission spectroscopy. The photocatalytic activity of the Bi7O9I3/RGO composite was evaluated by the degradation of rhodamine B (RhB) and phenol under visible irradiation (λ > 420 nm). The results indicated that the Bi7O9I3 nanoplates dispersed uniformly on RGO surface. The photocatalytic activity of Bi7O9I3/RGO in degradation of RhB and phenol was 2.13 and 2.29 times that of pure Bi7O9I3, respectively. The enhanced photocatalytic activity can be attributed to more effective charge transportations and separations, the high pollutant adsorption performance, and the increased light absorption. In addition, the Bi7O9I3/RGO photocatalyst was stable during the reaction and can be used repeatedly.

Confined Volume Change in Sn-Co-C Ternary Tube-in-Tube Composites for High-Capacity and Long-Life Lithium Storage

Co-reporter:Yan Gu;Fendan Wu

Advanced Functional Materials 2013 Volume 23( Issue 7) pp:893-899

Publication Date(Web):

DOI:10.1002/adfm.201202136

Abstract

All high capacity Li-alloy anodes for Li-ion battery suffer from enormous volume expansion and extraction during the lithium-ion insertion and extraction process. A Sn-Co-CNT@CNT ternary tube-in-tube nanostructure is prepared by an in situ template technique and shows perfect structure suitability to solve the critical volume change problem. The morphology, size, and quantity of the filled CNT-supported Sn-Co nanoparticles can be also tuned by adjusting the experimental conditions to achieve optimal electrochemical performances. The tube-in-tube product exhibits larger-than-theoretical reversible capacities of 890–811 mA h g⁻¹ at 0.1C in 200 cycles and excellent rate capability and high-rate cycling stability. The excellent electrochemical performance is mainly attributed to the confined volume change in the nanotube cavities and ensured permanent electrical connectivity of the immobilized Sn-Co anodes.

Sulfur film-coated reduced graphene oxide composite for lithium–sulfur batteries

Co-reporter:Li Qiang Lu, Li Jie Lu and Yong Wang

Journal of Materials Chemistry A 2013 vol. 1(Issue 32) pp:9173-9181

Publication Date(Web):24 May 2013

DOI:10.1039/C3TA11255A

This paper reports a cathode material of a graphene–sulfur film nanostructure synthesized by a facile wet chemical oxidation technique. The hybrid material is synthesized by using ferric chloride as an oxidizing agent and polysulfide as the sulfur source. The oxidizing agent FeCl3 is introduced as a soft film template to form a sulfur film on graphene oxide (GO). This is ascribed to the formation of a ferric cations double layer (FCDL) on the graphene oxide surface with many negative functional groups. Material characterizations reveal that GO is reduced to reduced graphene oxide (RGO) and the sulfur materials are embedded in a three dimensional conducting composite network of RGO and polyethylene glycol (PEG), forming a continuous sulfur film coating on RGO. When fabricated as a cathode material for rechargeable lithium ion batteries, the sulfur film-coated graphene composite electrode exhibits high capacity, improved Coulombic efficiency and extraordinarily stable cycling performance. It is believed that the sulfur film is coated on RGO and protected by the PEG network, and therefore the high solubility of the polysulfide anions formed as the reaction intermediate in the discharge and charge processes is relieved to a large extent. The electronic conductivity of insulating sulfur is also improved substantially in the RGO–S–PEG network.

Graphene-Wrapped CoS Nanoparticles for High-Capacity Lithium-Ion Storage

Co-reporter:Yan Gu, Yi Xu, and Yong Wang

ACS Applied Materials & Interfaces 2013 Volume 5(Issue 3) pp:801

Publication Date(Web):January 14, 2013

DOI:10.1021/am3023652

Graphene-wrapped CoS nanoparticles are synthesized by a solvothermal approach. The product is significantly different from porous CoS microspheres prepared in the absence of graphene under similar preparation conditions. The CoS microspheres and CoS/graphene composite are fabricated as anode materials for lithium-ion batteries. The CoS/graphene composite is found to be better suitable as an anode in terms of higher capacity and better cycling performances. The nanocomposite exhibits an unprecedented high reversible capacity of 1056 mA h/g among all cobalt sulfide-based anode materials. Good cycling performances are also observed at both small and high current rates.Keywords: anode; CoS; graphene nanosheets; lithium-ion battery; nanocomposite;

Interconnected Tin Disulfide Nanosheets Grown on Graphene for Li-Ion Storage and Photocatalytic Applications

Co-reporter:Peng Chen, Yun Su, Hong Liu, and Yong Wang

ACS Applied Materials & Interfaces 2013 Volume 5(Issue 22) pp:12073

Publication Date(Web):October 24, 2013

DOI:10.1021/am403905x

Reduced graphene oxide (RGO) nanosheet-supported SnS2 nanosheets are prepared by a one-step microwave-assisted technique. These SnS2 nanosheets are linked with each other and dispersed uniformly on RGO surface. The SnS2-RGO sheet-on-sheet nanostructure exhibits good electrochemical performances as an anode material for lithium ion batteries. It shows larger-than-theoretical reversible capacities at 0.1 C and excellent high-rate capability at 1 C and 5 C. The composite is also for the first time identified as an excellent visible light-driven catalyst of rhodamine B and phenol with high degradation efficiencies. The removal rates of rhodamine B and phenol are 100 and 83.2%, respectively, for the SnS2-RGO composite, whereas these values are only 64.8 and 51.5% for pristine SnS2 after the same irradiation times. The outstanding electrochemical or photocatalytic performances of the composite have been attributed to the complementary effect of RGO and SnS2 in the perfect sheet-on-sheet composition nanostructure.Keywords: lithium ion batteries; photocatalyst; reduced graphene oxide; sheet-on-sheet; SnS2 nanosheet;

Graphene wrapped SnCo nanoparticles for high-capacity lithium ion storage

Co-reporter:Peng Chen, Lei Guo, Yong Wang

Journal of Power Sources 2013 Volume 222() pp:526-532

Publication Date(Web):15 January 2013

DOI:10.1016/j.jpowsour.2012.09.026

Graphene nanosheets (GNS) wrapped SnCo alloy nanoparticles are prepared by a chemical reduction method on an ice water bath. SnCo nanoparticles are dispersed uniformly on GNS and their particle sizes are around 8-12 nm, which are substantially smaller than the pristine SnCo particles (∼80-180 nm) prepared in the absence of GNS. The GNS-SnCo composite is fabricated as an anode material for lithium ion batteries. It shows a distinguished higher-than-theoretical capacity of 1117 mAh g−1 at 72 mA g−1, which is larger than bare GNS (727 mAh g−1) or Sn-Co particles (599 mAh g−1). Moreover, the GNS-SnCo composite shows a good rate performance at a large current of 720 mA g−1. A high capacity of 922 mAh g−1 is retained with more stable cycle life than that at a small current. These improved cycling performances are attributed to the complimentary effect of three elements. The mechanical stability of Sn upon cycling is improved by the presence of robust and electrically conductive GNS and the alleviated function of inactive cobalt element. The agglomeration of GNS is also hindered by the spacing effect of SnCo nanoparticles among neighboring GNS materials.Highlights► Graphene-wrapped SnCo nanoparticles are prepared by a facile solution route. ► The composite shows an extremely high reversible capacity of 1117 mAh g-1 at 0.1C. ► It also exhibits good high-rate capability and cycling performances.

Microwave-assisted solvothermal synthesis of 3D carnation-like SnS2 nanostructures with high visible light photocatalytic activity

Co-reporter:Hong Liu, Yun Su, Peng Chen, Yong Wang

Journal of Molecular Catalysis A: Chemical 2013 Volume 378() pp:285-292

Publication Date(Web):1 November 2013

DOI:10.1016/j.molcata.2013.06.021

•3D carnation-flowerlike SnS2 hierarchical structures were synthesized.•The present synthetic approach is quite fast, simple and environmentally friendly.•The flowerlike SnS2 architectures exhibited high photocatalytic activity.•The flowerlike SnS2 architectures were stable and reusable in photocatalysis.Novel 3D carnation-flowerlike hexagonal SnS2 hierarchical structures have been successfully synthesized through a simple microwave-assisted solvothermal process. The as-prepared products were characterized by power X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution transmission electron micrographs (HRTEM), selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectra (DRS). The photocatalytic activity of the sample under visible-light irradiation (λ > 420 nm) was evaluated by the degradation of two different organic pollutants, rhodamine B (RhB) and phenol. The results reveal that the carnation-flowerlike SnS2 architectures show much higher photocatalytic activity than the SnS2 nanoparticles. The high catalytic performance of the SnS2 architectures comes from their hierarchical mesoporous structures, high BET surface area, high surface-to-volume ratios, and increased light absorbance. In addition, the SnS2 hierarchical architectures are stable during the photocatalytic reaction and can be used repeatedly.

Microwave hydrothermal synthesis of high performance tin–graphene nanocomposites for lithium ion batteries

Co-reporter:Shuangqiang Chen, Yong Wang, Hyojun Ahn, Guoxiu Wang

Journal of Power Sources 2012 Volume 216() pp:22-27

Publication Date(Web):15 October 2012

DOI:10.1016/j.jpowsour.2012.05.051

Tin–graphene nanocomposites are prepared by a combination of microwave hydrothermal synthesis and a one-step hydrogen gas reduction. Altering the weight ratio between tin and graphene nanosheets has critical influences on their morphologies and electrochemical performances. Field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) analysis confirm the homogeneous distribution of tin nanoparticles on the surface of graphene nanosheets. When applied as an anode material in lithium ion batteries, tin–graphene nanocomposite exhibits a high lithium storage capacity of 1407 mAh g−1. The as-prepared tin–graphene nanocomposite also demonstrates an excellent high rate capacity and a stable cycle performance. The superior electrochemical performance could be attributed to the synergistic effect of the three-dimensional nanoarchitecture, in which tin nanoparticles are sandwiched between highly conductive and flexible graphene nanosheets.Highlights► Sn–GNS were prepared by a microwave hydrothermal synthesis and a one-step H2 reduction. ► Sn nanoparticles are homogenously sandwiched between highly conductive and flexible GNS. ► Altering the ratio between tin and graphene had critical influences on their morphologies. ► Sn–GNS exhibited a high lithium storage capacity of 1407 mAh g−1.

Facile synthesis of graphene-supported shuttle- and urchin-like CuO for high and fast Li-ion storage

Co-reporter:Li Qiang Lu, Yong Wang

Electrochemistry Communications 2012 Volume 14(Issue 1) pp:82-85

Publication Date(Web):January 2012

DOI:10.1016/j.elecom.2011.11.010

Graphene nanosheet (GNS) supported shuttle- and urchin-like CuO nanostructures are prepared by a facile low-temperature solution route. CuO nanoshuttles or urchin-like nanostructures are dispersed uniformly on GNS, forming a three dimensional CuO–GNS layer-by-layer network after stacking. When fabricated as anode materials for lithium-ion batteries, CuO–GNS composites exhibit superior Li-ion storage properties in terms of high capacity, long cycle life, and excellent rate performance. At a large current of 700 mA/g, GNS-supported CuO nanoshuttles show a higher-than-theoretical capacity of 826 mAh/g after 100 cycles, which is even larger than the reversible capacity of 771 mAh/g achieved at 70 mA/g after 40 cycles.Highlights► CuO nanostructures are prepared on graphene nanosheets at a low temperature. ► The morphologies of CuO are tuned to be shuttle-like or urchin-like. ► The CuO–graphene composites show superior lithium-ion storage properties.

Carbon nanotubes grown in situ on graphene nanosheets as superior anodes for Li-ion batteries

Co-reporter:Shuangqiang Chen, Peng Chen and Yong Wang

Nanoscale 2011 vol. 3(Issue 10) pp:4323-4329

Publication Date(Web):30 Aug 2011

DOI:10.1039/C1NR10642B

Graphene and carbon nanotubes are intriguing alternative anode materials for lithium ion batteries. The prevention of graphene restacking and facilitation of lithium diffusion into CNTs with large aspect ratio are highly desirable for the performance enhancements including capacity, cycliability and rate capability. In this work, we demonstrated that a multilayered graphene-CNT hybrid nanostructure was able to hold such merits. GNS were separated and stabilized by CNTs grown in situ on GNS surface. The length of CNTs was found to be a key factor to the electrochemical performances. The GNS-CNT composite with the shortest CNT decoration displayed highly reversible capacities of 573 mAh g−1 at a small current of 0.2C and 520 mAh g−1 at a large current of 2C. The growth and lithium storage mechanism for graphene-CNT composite was also proposed.

Self-assembled echinus-like nanostructures of mesoporous CoO nanorod@CNT for lithium-ion batteries

Co-reporter:Feng Dan Wu and Yong Wang

Journal of Materials Chemistry A 2011 vol. 21(Issue 18) pp:6636-6641

Publication Date(Web):25 Mar 2011

DOI:10.1039/C0JM04346J

Development of an electrode material with high capacity and good cyclability at a high charge and discharge rate, has become an important issue for present battery technology. Most electrode materials exhibit reduced capacity and larger capacity fading at high rates. We report a self-assembled echinus-like nanostructure consisting of mesoporous CoO nanorod@carbon nanotube core–shell materials in this work, which exhibits high capacities and excellent cycling performances at various high and low current rates, when used as anode materials for rechargeable lithium ion batteries. In particular, this core–shell nanostructure shows high capacities (703–746 mAh g−1 in 200 cycles) and a long cycle life (0.029% capacity loss per cycle) at a high current rate (3580 mA g−1). The excellent electrochemical energy storage should be attributed to the increased electrical conductivity, mechanical stability and electrochemical activity of porous CoO materials in the presence of a carbon nanotube overlayer.

Sheet-like and fusiform CuO nanostructures grown on graphene by rapid microwave heating for high Li-ion storage capacities

Co-reporter:Li Qiang Lu and Yong Wang

Journal of Materials Chemistry A 2011 vol. 21(Issue 44) pp:17916-17921

Publication Date(Web):11 Oct 2011

DOI:10.1039/C1JM12589C

This paper reports CuO-graphene layer-by-layer hybrid nanostructures by a fast microwave irradiation method. The CuO nanosheets or fusiform morphologies were obtained by varying the reaction temperature of microwave heating. These CuO nanostructures were uniformly dispersed on graphene nanosheets (GNS), forming layer-by-layer nanostructures after drying and stacking. CuO nanostructures were designed as the spacer to prevent the reassembly of GNS to graphite sheets so that the unique properties relative to few-layer graphene nanosheets (GNS) could be retained in the practical applications. When evaluated as anode materials for Li-ion batteries, the CuO-GNS composites showed substantially enhanced lithium-storage capacities compared to CuO materials and GNS, which has been attributed to the improvement of structure stability and electrical contact by GNS for a long time upon repetitive cycling.

NiO nanosheets grown on graphene nanosheets as superior anode materials for Li-ion batteries

Co-reporter:Yuqin Zou and Yong Wang

Nanoscale 2011 vol. 3(Issue 6) pp:2615-2620

Publication Date(Web):26 Apr 2011

DOI:10.1039/C1NR10070J

This paper reports a hydrothermal preparation of NiO–graphene sheet-on-sheet and nanoparticle-on-sheet nanostructures. The sheet-on-sheet nanocomposite showed highly reversible large capacities at a common current of 0.1 C and good rate capabilities. A large initial charge capacity of 1056 mAh/g was observed for the sheet-on-sheet composite at 0.1 C, which decreased by only 2.4% to 1031 mAh/g after 40 cycles of discharge and charge. This cycling performance is better than that of NiO nanosheets, graphene nanosheets, NiO-graphene nanoparticle-on-sheet, and previous carbon/carbon nanotube supported NiO composites. It is believed that the mechanical stability and electrical conductivity of NiO nanosheets are increased by graphene nanosheets (GNS), the aggregation or restacking of which to graphite platelets are, on the other hand, effectively prevented by NiO nanosheets.

Antimony-doped tin oxide nanotubes for high capacity lithium storage

Co-reporter:Feng Dan Wu, Minghong Wu, Yong Wang

Electrochemistry Communications 2011 Volume 13(Issue 5) pp:433-436

Publication Date(Web):May 2011

DOI:10.1016/j.elecom.2011.02.013

Antimony-doped tin oxide (ATO) nanotubes were synthesized by a modified template method in this work. The nanotubes, which were ~ 200 nm in diameter and 10–20 nm in wall thickness, were composed of a large number of 5–15 nm ATO nanocrystals. The doping level of Sb in the ATO could be varied by the experimental conditions. ATO nanotubes with Sn:Sb ratios of 9:1 or 5:1, in particular, were good reversible Li storage materials, showing high capacities and good cyclability at both common and high rates of charge and discharge.Research Highlights► Antimony-doped tin oxide (ATO) nanotubes are prepared by a template method. ► ATO nanotubes show good lithium-ion storage properties. ► The electrode stability is improved by the Sb doping and tubular shape.

Microwave-assisted synthesis of porous nickel oxide nanostructures as anode materials for lithium-ion batteries

Co-reporter:Yuqin Zou

Rare Metals 2011 Volume 30( Issue 1 Supplement) pp:59-62

Publication Date(Web):2011 March

DOI:10.1007/s12598-011-0238-0

A self-assembled porous NiO nanorod nanocluster was reported in this work, which was prepared with the assistance of microwave-irradiation for 1–4 min. The obtained NiO nanocluster consistes of a few NiO nanorods, which are about 2–5 μm in length and 50–200 nm in diameter. The product were characterized by XRD, SEM and TEM and based on the observation it is believed that NiO nanoparticles are the building blocks to construct the structure of nanorod nanocluster. The NiO nanorod nanocluster is also fabricated as an anode material for rechargeable lithium ion batteries, which shows a high reversible capacity and good cycle life.

Sn@CNT Nanostructures Rooted in Graphene with High and Fast Li-Storage Capacities

Co-reporter:Yuqin Zou and Yong Wang

ACS Nano 2011 Volume 5(Issue 10) pp:8108

Publication Date(Web):September 22, 2011

DOI:10.1021/nn2027159

Development of materials with carefully crafted nanostructures has been an important strategy for the next-generation lithium-ion batteries to achieve higher capacity, longer cycle life, and better rate capability. Graphene-based and Sn-based anode materials are promising anodes with higher capacities than graphite; however, most of them exhibit fast capacity fading at prolonged cycling and poor rate capability. This paper reports a hierarchical Sn@CNT nanostructure rooted in graphene, which exhibits larger than theoretical reversible capacities of 1160–982 mAh/g in 100 cycles at 100 mA/g and excellent rate capability (828 mAh/g at 1000 mA/g and 594 mAh/g at 5000 mA/g). The excellent electrochemical performances compared to graphene/Sn-based anodes have been attributed to the efficient prevention of graphene agglomeration by Sn@CNT decoration and the increased electrochemical activities of Sn by CNT shell protection and GNS support.Keywords: carbon nanotube; graphene; lithium ion batteries; Sn; SnS2

Fe2O3-Graphene Rice-on-Sheet Nanocomposite for High and Fast Lithium Ion Storage

Co-reporter:Yuqin Zou ; Jin Kan

The Journal of Physical Chemistry C 2011 Volume 115(Issue 42) pp:20747-20753

Publication Date(Web):September 14, 2011

DOI:10.1021/jp206876t

Graphene nanosheet (GNS)-supported Fe2O3 nanorice and nanoparticles were synthesized by a microwave-assisted hydrothermal technique. The Fe2O3-GNS rice-on-sheet composite showed a better suitability as an anode material for Li-ion batteries. It exhibited a very large reversible capacity of 1184 mAh/g at a small current of 100 mA/g as well as good cycling performances. A good rate capability was also observed for Fe2O3-GNS rice-on-sheet composite, which exhibited large capacities of 825 and 633 mAh/g at large currents of 1000 and 5000 mA/g, respectively. The outstanding electrochemical behavior was ascribed to the increased electrical conductivity and mechanical stability of Fe2O3 nanorice by GNS support and prevented aggregation of few-layer GNS by the Fe2O3 decoration during the repetitive cycling with lithium ions.

Ionic liquid-templated synthesis of mesoporous CeO2–TiO2 nanoparticles and their enhanced photocatalytic activities under UV or visible light

Co-reporter:Hong Liu, Mengyang Wang, Yong Wang, Yuguang Liang, Weiran Cao, Yun Su

Journal of Photochemistry and Photobiology A: Chemistry 2011 Volume 223(2–3) pp:157-164

Publication Date(Web):25 September 2011

DOI:10.1016/j.jphotochem.2011.06.014

Mesostructrured CeO2–TiO2 nanoparticles with different CeO2 contents have been successfully synthesized using ionic liquid (1-hexadecane-3-methylimidazolium bromide, C16MIM+Br−) as a template by a hydrothermal method. The prepared materials were characterized by means of X-ray diffraction (XRD), nitrogen adsorption–desorption, transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectra analysis. The obtained CeO2–TiO2 materials exhibit large specific surface area and uniform pore sizes. Introduction of CeO2 species can effectively extend the spectral response from UV to visible area and enhance the surface hydroxyl groups of the mesoporous TiO2. The CeO2–TiO2 nanocomposites show high photocatalytic activity in the degradation of the p-chlorophenol aqueous solution under the UV or visible irradiation.Graphical abstractHighlights► Well-crystallized mesoporous CeO2–TiO2 can be obtained. ► Such material exhibits strong spectral response in the visible region. ► Introduction of CeO2 species enhances the surface hydroxyl groups of the catalyst. ► The obtained material shows high photocatalytic activity under UV or visible light.

Microwave-assisted synthesis of a Co3O4–graphene sheet-on-sheet nanocomposite as a superior anode material for Li-ion batteries

Co-reporter:Shuang Qiang Chen and Yong Wang

Journal of Materials Chemistry A 2010 vol. 20(Issue 43) pp:9735-9739

Publication Date(Web):20 Sep 2010

DOI:10.1039/C0JM01573C

This paper reports the microwave-assisted synthesis of a Co3O4–graphene sheet-on-sheet nanostructure. This sheet-on-sheet nanocomposite showed an excellent high rate capability and highly reversible large capacity at common rate. A capacity of 931 mA h g−1 was observed at a large current rate of 5C (4450 mA g−1), which was still larger than the theoretical capacity of Co3O4 (890 mAh g−1). The substantially improved electrochemical properties were ascribed to the unique sheet-on-sheet nanostructure. Co3O4 nanosheets were tightly stacked with graphene nanosheets (GNS), therefore volume changes of Co3O4 materials were accommodated in the presence of GNS. On the other hand, sheet-like Co3O4 was very effective to prevent the reassembly of GNS to graphite platelets, thus preserving GNS advantages during repetitive cycling.

Graphene supported Sn–Sb@carbon core-shell particles as a superior anode for lithium ion batteries

Co-reporter:Shuangqiang Chen, Peng Chen, Minghong Wu, Dengyu Pan, Yong Wang

Electrochemistry Communications 2010 Volume 12(Issue 10) pp:1302-1306

Publication Date(Web):October 2010

DOI:10.1016/j.elecom.2010.07.005

This paper reports the preparation and Li-storage properties of graphene nanosheets(GNS), GNS supported Sn–Sb@carbon (50–150 nm) and Sn–Sb nanoparticles (5–10 nm). The best cycling performance and excellent high rate capabilities were observed for GNS-supported Sn–Sb@carbon core-shell particles, which exhibited initial capacities of 978, 850 and 668 mAh/g respectively at 0.1C, 2C and 5C (1C = 800 mA/g) with good cyclability. Besides the GNS support, the carbon skin around Sn–Sb particles is believed to be a key factor to improve electrochemical properties of Sn–Sb.

Macroporous Co3O4 platelets with excellent rate capability as anodes for lithium ion batteries

Co-reporter:Yan Lu, Yong Wang, Yuqin Zou, Zheng Jiao, Bing Zhao, Yaqin He, Minghong Wu

Electrochemistry Communications 2010 Volume 12(Issue 1) pp:101-105

Publication Date(Web):January 2010

DOI:10.1016/j.elecom.2009.10.046

This paper reports the microwave-assisted synthesis of Co3O4 nanomaterials with different morphologies including nanoparticles, rod-like nanoclusters and macroporous platelets. The new macroporous platelet-like Co3O4 morphology was found to be the best suitable for reversible lithium storage properties. It displayed superior cycling performances than nanoparticles and rod-like nanoclusters. More interestingly, excellent high rate capabilities (811 mAh g−1 at 1780 mA g−1 and 746 mAh g−1 at 4450 mA g−1) were observed for macroporous Co3O4 platelet. The good electrochemical performance could be attributed to the unique macroporous platelet structure of Co3O4 materials.

Indium Tin Oxide@Carbon Core–Shell Nanowire and Jagged Indium Tin Oxide Nanowire

Co-reporter:Yong Wang;Liqiang Lu;Fengdan Wu

Nanoscale Research Letters 2010 Volume 5( Issue 10) pp:

Publication Date(Web):2010 October

DOI:10.1007/s11671-010-9695-x

This paper reports two new indium tin oxide (ITO)-based nanostructures, namely ITO@carbon core–shell nanowire and jagged ITO nanowire. The ITO@carbon core–shell nanowires (~50 nm in diameter, 1–5 μm in length,) were prepared by a chemical vapor deposition process from commercial ITO nanoparticles. A carbon overlayer (~5–10 in thickness) was observed around ITO nanowire core, which was in situ formed by the catalytic decomposition of acetylene gas. This carbon overlayer could be easily removed after calcination in air at an elevated temperature of 700°C, thus forming jagged ITO nanowires (~40–45 nm in diameter). The growth mechanisms of ITO@carbon core–shell nanowire and jagged ITO nanowire were also suggested.

Sn@CNT and Sn@C@CNT nanostructures for superior reversible lithium ion storage

Co-reporter:Yong Wang, Minghong Wu, Zheng Jiao and Jim Yang Lee

Chemistry of Materials 2009 Volume 21(Issue 14) pp:3210

Publication Date(Web):June 25, 2009

DOI:10.1021/cm900702d

In this study we demonstrate a facile templated chemical vapor deposition (CVD) method to produce CNT-encapsulated Sn nanoparticles with ∼100% particle encapsulation and high filling uniformity. The encapsulated Sn particles were formed either as Sn or Sn@carbon core−shell particles with good control of size and morphology. The complete and uniform encapsulation of small, electrochemically active Sn particles within a CNT matrix with large free volume accommodated the volume excursion problem in repetitive lithium insertion and extraction reactions very well, showing good resilience in maintaining electrical connective and mechanical integrity. Consequently the completely filled Sn@CNT nanocomposite showed excellent reversible lithium ion storage properties.

Self-assembly nanostructures of one-dimensional antimony oxide and oxychloride

Co-reporter:Jun-Jun Tang, Yong Wang, Zheng Jiao, Minghong Wu

Materials Letters 2009 Volume 63(Issue 17) pp:1481-1484

Publication Date(Web):15 July 2009

DOI:10.1016/j.matlet.2009.03.044

This paper reports a facile solution route (water bath heating or hydrothermal heating) for synthesizing a few Sb-based self-assembly structures including bundles of nanowires, nanowire-flowers, long nanowires, bundles of flakes, nanobelts, hollow prisms. These obtained nanomaterials were characterized by XRD, FE-SEM, TEM, SAED, and HRTEM. It was found that the morphology, size and phase of self-assembly nanostructures were strongly dependent on reaction temperature, reaction time, pH value, and heating source. In particular, nanowire-flowers and hollow prisms of antimony oxide or oxychloride have not been reported previously. A possible mechanism based on stepwise nucleation and aggregation of nanowires or flakes was also proposed.

Recent developments of aprotic lithium-oxygen batteries: functional materials determine the electrochemical performance

Co-reporter:Xin Guo, Bing Sun, Dawei Su, Xiaoxue Liu, ... Guoxiu Wang

Science Bulletin (30 March 2017) Volume 62(Issue 6) pp:442-452

Publication Date(Web):30 March 2017

DOI:10.1016/j.scib.2017.01.037

Lithium oxygen battery has the highest theoretical capacity among the rechargeable batteries and it can reform energy storage technology if it comes to commercialization. However, many critical challenges, mainly embody as low charge/discharge round-trip efficiency and poor cycling stability, impede the development of Li-O2 batteries. The electrolyte decomposition, lithium metal anode corrosion and sluggish oxygen reaction kinetics at cathode are all responsible for poor electrochemical performances. Particularly, the catalytic cathode of Li-O2 batteries, playing a crucial role to reduce the oxygen during discharging and to decompose discharge products during charging, is regarded as a breakthrough point that has been comprehensive investigated. In this review, the progress and issues of electrolyte, anode and cathode, especially the catalysts used at cathode, are systematically summarized and discussed. Then the perspectives toward the developments of a long life Li-O2 battery are also presented at last.

MOF-templated nanorice–nanosheet core–satellite iron dichalcogenides by heterogeneous sulfuration for high-performance lithium ion batteries

Co-reporter:Huicong Pang, Weiwei Sun, Li-Ping Lv, Feiying Jin and Yong Wang

Journal of Materials Chemistry A 2016 - vol. 4(Issue 48) pp:NaN19188-19188

Publication Date(Web):2016/11/11

DOI:10.1039/C6TA09060E

Metal dichalcogenides are promising electrode materials for lithium-ion batteries (LIBs) because of their large specific capacities. Their electrochemical properties are largely dependent on their composition, morphology and porosity. This paper reports a metal–organic framework (MOF) synthetic approach for achieving a nanorice–nanosheet core–satellite structure of sulfur-doped porous carbon coated FeS2 (FeS2@S-C NR-NS (MOF)). Unlike substantial morphology transformation in the sulfuration process from common Fe-based precursors, the nanorice skeleton can be inherited from the Fe-MOF precursor, while small nanosheets are formed on the exterior surface due to heterogeneous sulfuration. When evaluated as the anode material for LIBs, FeS2@S-C NR-NS (MOF) exhibits excellent cycling performances with a larger-than-theoretical reversible capacity of 1336.5 mA h g−1 after 200 cycles at 100 mA g−1 and good high-rate capability. The improved structural stability, electrical conductivity and enhanced kinetic rate of ions and electrons have been attributed to the hierarchical structure, porous characteristics, and S-doped carbon overlayer in the electrode.

MOF-derived yolk–shell CdS microcubes with enhanced visible-light photocatalytic activity and stability for hydrogen evolution

Co-reporter:Yun Su, Dan Ao, Hong Liu and Yong Wang

Journal of Materials Chemistry A 2017 - vol. 5(Issue 18) pp:NaN8689-8689

Publication Date(Web):2017/04/05

DOI:10.1039/C7TA00855D

Microwave-assisted synthesis of a Co3O4–graphene sheet-on-sheet nanocomposite as a superior anode material for Li-ion batteries

Co-reporter:Shuang Qiang Chen and Yong Wang

Journal of Materials Chemistry A 2010 - vol. 20(Issue 43) pp:NaN9739-9739

Publication Date(Web):2010/09/20

DOI:10.1039/C0JM01573C

NiS nanorod-assembled nanoflowers grown on graphene: morphology evolution and Li-ion storage applications

Co-reporter:Hua Geng, Shao Feng Kong and Yong Wang