Showing papers by "Yong Wang published in 2014"

Graphene-based nanocomposite anodes for lithium-ion batteries

Abstract: Graphene-based nanocomposites have been demonstrated to be promising high-capacity anodes for lithium ion batteries to satisfy the ever-growing demands for higher capacity, longer cycle life and better high-rate performance. Synergetic effects between graphene and the introduced second-phase component are generally observed. In this feature review article, we will focus on the recent work on four different categories of graphene-based nanocomposite anodes by us and others: graphene-transitional metal oxide, graphene–Sn/Si/Ge, graphene–metal sulfide, and graphene–carbon nanotubes. For the supported materials on graphene, we will emphasize the non-zero dimensional (non-particle) morphologies such as two dimensional nanosheet/nanoplate and one dimensional nanorod/nanofibre/nanotube morphologies. The synthesis strategies and lithium-ion storage properties of these highlighted electrode morphologies are distinct from those of the commonly obtained zero dimensional nanoparticles. We aim to stress the importance of structure matching in the composites and their morphology-dependent lithium-storage properties and mechanisms.

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

Abstract: 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-o...

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

Abstract: 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.

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

Abstract: Bi 7 O 9 I 3 /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 Bi 7 O 9 I 3 /RGO composite was evaluated by the degradation of rhodamine B (RhB) and phenol under visible irradiation ( λ > 420 nm). The results indicated that the Bi 7 O 9 I 3 nanoplates dispersed uniformly on RGO surface. The photocatalytic activity of Bi 7 O 9 I 3 /RGO in degradation of RhB and phenol was 2.13 and 2.29 times that of pure Bi 7 O 9 I 3 , 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 Bi 7 O 9 I 3 /RGO photocatalyst was stable during the reaction and can be used repeatedly.

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

Abstract: 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.

Four-layer tin-carbon nanotube yolk-shell materials for high-performance lithium-ion batteries.

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.

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

Abstract: 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.

High-Performance Removal of Phosphate from Water by Graphene Nanosheets Supported Lanthanum Hydroxide Nanoparticles

Abstract: A novel high-capacity phosphate removal adsorbent of graphene nanosheets (GNS) supported lanthanum hydroxide (LaOH) is prepared. The phosphate adsorption performance for GNS-LaOH is examined by a batch adsorption method from aqueous solutions. The Freundlich and Langmuir models are used to simulate the sorption equilibrium, which reveal that the Langmuir model has a better correlation with the experimental data. The maximum adsorption capacity is calculated to be 41.96 mg/g. The kinetic data from the adsorption of phosphate is suggested as the pseudo-second-order model, and the multi-linearity adsorption process is observed in the intraparticle diffusion model, indicating that a chemisorption process is dominant in the adsorption of phosphate. The phosphate adsorption mechanism is explored by analyzing the Fourier transform infrared spectroscopy (FT-IR) and the relationship between the adsorption amount and the pH value of phosphate solution. Ligand exchange and electrostatic and Lewis acid–base interactions are determined to be three main factors for phosphate adsorption.

Self-Assembly Behaviors of Heterogemini Surfactant in Aqueous Solution Investigated by Dissipative Particle Dynamics

Abstract: As a preliminary study, self-assembly behaviors of heterogemini surfactant in aqueous solution are explored tentatively by means of dissipative particle dynamics simulation. Five kinds of heterogemini molecules are involved, and a variety of novel morphologies have been obtained. Results based on detailed comparisons among themselves and with traditional symmetric gemini surfactant show the proportion of hydrophilic to hydrophobic chain lengths in one monomer is the most important, more difference between proportions in the two monomers can induce more diverse self-assembly morphologies. The second important is the hydrophilic chain length, in which a small change can lead to obvious difference in self-assembly behaviors. While the length of hydrophobic chain has a less important influence, only the concentration for self-assembly morphologies appearing can be affected by its change. The microscopic morphology of heterogemini surfactant in its self-assembly structure can be embodied through its radius of ...