Showing papers on "Nanotube published in 2015"

Mechanical properties of carbon nanotube/polymer composites

Abstract: The remarkable mechanical properties of carbon nanotubes, such as high elastic modulus and tensile strength, make them the most ideal and promising reinforcements in substantially enhancing the mechanical properties of resulting polymer/carbon nanotube composites. It is acknowledged that the mechanical properties of the composites are significantly influenced by interfacial interactions between nanotubes and polymer matrices. The current challenge of the application of nanotubes in the composites is hence to determine the mechanical properties of the interfacial region, which is critical for improving and manufacturing the nanocomposites. In this work, a new method for evaluating the elastic properties of the interfacial region is developed by examining the fracture behavior of carbon nanotube reinforced poly (methyl methacrylate) (PMMA) matrix composites under tension using molecular dynamics simulations. The effects of the aspect ratio of carbon nanotube reinforcements on the elastic properties, i.e. Young's modulus and yield strength, of the interfacial region and the nanotube/polymer composites are investigated. The feasibility of a three-phase micromechanical model in predicting the elastic properties of the nanocomposites is also developed based on the understanding of the interfacial region.

Controllable Synthesis of Mesoporous Peapod-like Co3O4@Carbon Nanotube Arrays for High-Performance Lithium-Ion Batteries†

Abstract: Transition metal oxides are regarded as promising anode materials for lithium-ion batteries because of their high theoretical capacities compared with commercial graphite. Unfortunately, the implementation of such novel anodes is hampered by their large volume changes during the Li+ insertion and extraction process and their low electric conductivities. Herein, we report a specifically designed anode architecture to overcome such problems, that is, mesoporous peapod-like Co3O4@carbon nanotube arrays, which are constructed through a controllable nanocasting process. Co3O4 nanoparticles are confined exclusively in the intratubular pores of the nanotube arrays. The pores between the nanotubes are open, and thus render the Co3O4 nanoparticles accessible for effective electrolyte diffusion. Moreover, the carbon nanotubes act as a conductive network. As a result, the peapod-like Co3O4@carbon nanotube electrode shows a high specific capacity, excellent rate capacity, and very good cycling performance.

Fabrication of Spinel One-Dimensional Architectures by Single-Spinneret Electrospinning for Energy Storage Applications

Abstract: A facile and general method is developed to fabricate one-dimensional (1D) spinel composite oxides with complex architectures by using a facile single-spinneret electrospinning technique. It is found that precursor polymers and heating rates could control the structures of the products, such as 1D solid, nanotube and tube-in-tubes structures. Especially, the tube-in-tube structures have been successfully fabricated for various mixed metal oxide, including CoMn2O4, NiCo2O4, CoFe2O4, NiMn2O4 and ZnMn2O4. Benefiting from the unique structure features, the tube-in-tube hollow nanostructures possess superior electrochemical performances in asymmetric supercapacitors and Li–O2 batteries.

Flexible, Stretchable, and Rechargeable Fiber-Shaped Zinc-Air Battery Based on Cross-Stacked Carbon Nanotube Sheets.

Abstract: The fabrication of flexible, stretchable and rechargeable devices with a high energy density is critical for next-generation electronics. Herein, fiber-shaped Zn-air batteries, are realized for the first time by designing aligned, cross-stacked and porous carbon nanotube sheets simultaneously that behave as a gas diffusion layer, a catalyst layer, and a current collector. The combined remarkable electronic and mechanical properties of the aligned carbon nanotube sheets endow good electrochemical properties. They display excellent discharge and charge performances at a high current density of 2 A g(-1) . They are also flexible and stretchable, which is particularly promising to power portable and wearable electronic devices.

Metal–Organic Polymers Containing Discrete Single-Walled Nanotube as a Heterogeneous Catalyst for the Cycloaddition of Carbon Dioxide to Epoxides

Abstract: The cycloaddition of carbon dioxide to epoxides to produce cyclic carbonates is quite promising and does not result in any side products. A discrete single-walled metal-organic nanotube was synthesized by incorporating a tetraphenyl-ethylene moiety as the four-point connected node. The assembled complex has a large cross-section, with an exterior wall diameter of 3.6 nm and an interior channel diameter of 2.1 nm. It features excellent activity toward the cycloaddition of carbon dioxide, with a turnover number of 17,500 per mole of catalyst and an initial turnover frequency as high as 1000 per mole of catalyst per hour. Only minimal decreases in the catalytic activity were observed after 70 h under identical reaction conditions, and a total turnover number as high as 35,000 was achieved. A simple comparison of relative porous MOFs suggested that the cross-section of the channels is an important factor influencing the transport of the substrates and products through the channel.

Photocatalytic Reduction of Carbon Dioxide by Hydrous Hydrazine over Au–Cu Alloy Nanoparticles Supported on SrTiO3/TiO2 Coaxial Nanotube Arrays

Abstract: Efficient photocatalytic conversion of CO2 into CO and hydrocarbons by hydrous hydrazine (N2H4⋅H2O) is achieved on SrTiO3/TiO2 coaxial nanotube arrays loaded with Au-Cu bimetallic alloy nanoparticles. The synergetic catalytic effect by the Au-Cu alloy nanoparticles and the fast electron-transfer in SrTiO3/TiO2 coaxial nanoarchitecture are the main reasons for the efficiency, while N2H4⋅H2O as the H source and electron donor provides a reducing atmosphere to protect the surface Cu atoms from oxidation, therefore maintaining the alloying effect which is the basis for the high photocatalytic activity and stability. This approach opens a feasible route to enhance the photocatalytic efficiency, which also benefits the development of photocatalysts and co-catalysts.

Advanced Sodium Ion Battery Anode Constructed via Chemical Bonding between Phosphorus, Carbon Nanotube, and Cross-Linked Polymer Binder

Abstract: Maintaining structural stability is a great challenge for high-capacity conversion electrodes with large volume change but is necessary for the development of high-energy-density, long-cycling batteries. Here, we report a stable phosphorus anode for sodium ion batteries by the synergistic use of chemically bonded phosphorus–carbon nanotube (P–CNT) hybrid and cross-linked polymer binder. The P–CNT hybrid was synthesized through ball-milling of red phosphorus and carboxylic group functionalized carbon nanotubes. The P–O–C bonds formed in this process help maintain contact between phosphorus and CNTs, leading to a durable hybrid. In addition, cross-linked carboxymethyl cellulose–citric acid binder was used to form a robust electrode. As a result, this anode delivers a stable cycling capacity of 1586.2 mAh/g after 100 cycles, along with high initial Coulombic efficiency of 84.7% and subsequent cycling efficiency of ∼99%. The unique electrode framework through chemical bonding strategy reported here is potenti...

Stretchable, weavable coiled carbon nanotube/MnO2/polymer fiber solid-state supercapacitors.

Abstract: Stretchable, Weavable Coiled Carbon Nanotube/MnO 2 /Polymer Fiber Solid-State Supercapacitors

Hierarchical Configuration of NiCo2S4 Nanotube@Ni–Mn Layered Double Hydroxide Arrays/Three-Dimensional Graphene Sponge as Electrode Materials for High-Capacitance Supercapacitors

Abstract: Three dimensional (3D) hierarchical network configurations are composed of NiCo2S4 nanotube @Ni–Mn layered double hydroxide (LDH) arrays in situ grown on graphene sponge. The 3D graphene sponge with robust hierarchical porosity suitable for as a basal growth has been obtained from a colloidal dispersion of graphene oxide using a simple directional freeze-drying technique. The high conductive NiCo2S4 nanotube arrays grown on 3D graphene shows excellent pseudocapacity and good conductive support for high-performance Ni–Mn LDH. The 3D NiCo2S4@Ni–Mn LDH/GS shows a high specific capacitance (Csp) 1740 mF cm–2 at 1 mA cm–2, even at 10 mA cm–2, 1267.9 mF cm–2 maintained. This high-performance composite electrode proposes a new and feasible general pathway as 3D electrode configuration for energy storage devices.

Plasmon-induced photoelectrocatalytic activity of Au nanoparticles enhanced TiO2 nanotube arrays electrodes for environmental remediation

Abstract: A pulse electrodeposition (PED) technique was adopted to construct highly dispersed Au nanoparticles (Au-NPs) on TiO 2 nanotube arrays (TiO 2 -NTs) electrodes prepared by electrochemical anodic oxidation. Both the particle size and loading amount were facilely controlled via adjusting electrochemical parameters. The morphology, crystallinity, elemental composition and light absorption capability of as-obtained Au/TiO 2 -NTs were distinguished based on various characterizations. Compared with pure TiO 2 -NTs, Au/TiO 2 -NTs electrodes exhibited much higher photocurrent density and greatly enhanced photoelectrocatalytic (PEC) activity towards the degradation of methyl orange (MO) under visible-light irradiation ( λ > 420 nm). The synergy effect between nanotubular structures of TiO 2 and uniformly dispersed Au nanoparticles, as well as the small bias potential and strong interaction between Au and TiO 2 , facilitated the Au plasmon-induced charge separation and transfer, which lead to highly efficient and stable visible-light PEC activity.

One-step hydrothermal green synthesis of silver nanoparticle-carbon nanotube reduced-graphene oxide composite and its application as hydrogen peroxide sensor

Abstract: A novel sensing composite of silver nanoparticles (AgNPs)-reduced graphene oxide (rGO)-carbon nanotube (MWCNT) was successfully synthesized by a simple one-step hydrothermal method without reducing agent. Mild reduction of GO was carried out under hydrothermal condition. While most conventional approaches make use of multistep chemical methods wherein strong reducing agents, such as hydrazine, hydroquinone, and sodium borohydride are employed, our method provides the notable advantage of a single-step reaction without employing any toxic solvent or reducing agent by providing a novel green synthetic route to produce the nanocomposites of rGO, carbon nanotube and silver. The results of X-ray diffraction (XRD) and Fourier-transform infrared transmission spectroscopy (FT-IR) confirmed the simultaneous formation of silver nanoparticles in the GO and MWCNT matrix. Field emission scanning electron microscope (FESEM) images and transmission electron microscopy (TEM) showed uniform distribution of nanometer-sized silver nanoparticles and narrow-sized MWCNT on GO sheets, which was achieved using silver ammonia complex as the precursor, instead of the commonly used silver nitrate. The composite exhibited excellent electrocatalytic activity for the reduction of H2O2 with a fast amperometric response time less than 3 s. The electrocatalytic activity for the reduction was strongly affected by the concentration of silver ammonia solution in the nanocomposites, with the best electrocatalytic activity observed for the composite of 6:1 volume ratios of MWCNT–GO (3:1, v/v) to Ag(NH3)2OH (0.04 M). The corresponding calibration curve for the current response showed a linear detection range of 0.1–100 mM (R2 = 0. 9985), while the limit of detection was estimated to be 0.9 μM.

Double-Shelled CdS- and CdSe-Cosensitized ZnO Porous Nanotube Arrays for Superior Photoelectrocatalytic Applications.

Abstract: The effective separation and transport of photoinduced electron–hole pairs in photoanodes is of great significance to photoelectrochemical and catalytic performance. Here, a facile and effective two-step strategy is developed to fabricate double-shelled ZnO/CdS/CdSe porous nanotube photoanodes from ZnO nanorod arrays (NRAs). Surprisingly, after the process of the deposition of CdS and CdSe, the ZnO nanorod arrays are partially dissolved, resulting in the formation of ZnO/CdS/CdSe porous nanotube arrays (NTAs). By virtue of their unique porous nanotube structure and cosensitization effect, the ZnO/CdS/CdSe porous NTAs show superior photoelectrochemical water-splitting performance and organic-pollutant-degradation ability under visible light irradiation, as well as excellent long-term photostability.

A super-high energy density asymmetric supercapacitor based on 3D core–shell structured NiCo-layered double hydroxide@carbon nanotube and activated polyaniline-derived carbon electrodes with commercial level mass loading

Abstract: Realization of high cell energy density at high mass loading is a critical requirement for the practical applications of supercapacitors. To date, the cell energy density of supercapacitor devices has been mainly limited by the low utilization efficiency of electroactive materials on positive electrodes at high mass loading and the low capacitance value of common activated carbon materials on negative electrodes. In this study, a super-high energy density asymmetric supercapacitor device with commercial mass loading was successfully fabricated by using a 3D core–shell structured NiCo-layered double hydroxide@carbon nanotube (NiCo-LDH@CNT) composite as the positive electrode and activated polyaniline-derived carbon (APDC) as the negative electrode. Due to its unique core–shell structure, the NiCo-LDH@CNT/nickel foam (NF) electrode with a mass loading of 8.5 mg cm−2 delivered a high capacitance of 2046 F g−1 at 1 A g−1, and still retained a high capacitance of 1335 F g−1 as the current density increased up to 15 A g−1. Coupled with the high performance APDC-based negative electrode with a capacitance of 487 F g−1 at 1 A g−1, the asymmetric NiCo-LDHs@CNT/NF//APDC/NF supercapacitor device delivered a maximum energy density of 89.7 W h kg−1 with an operational voltage of 1.75 V, and a maximum power density of 8.7 kW kg−1 at an energy density of 41.7 W h kg−1, suggesting its promising applications in future.

High-Yield and Selective Photoelectrocatalytic Reduction of CO2 to Formate by Metallic Copper Decorated Co3O4 Nanotube Arrays

Abstract: Carbon dioxide (CO2) reduction to useful chemicals is of great significance to global climate and energy supply. In this study, CO2 has been photoelectrocatalytically reduced to formate at metallic Cu nanoparticles (Cu NPs) decorated Co3O4 nanotube arrays (NTs) with high yield and high selectivity of nearly 100%. Noticeably, up to 6.75 mmol·L–1·cm–2 of formate was produced in an 8 h photoelectrochemical process, representing one of the highest yields among those in the literature. The results of scanning electron microscopy, transmission electron microscopy and photoelectrochemical characterization demonstrated that the enhanced production of formate was attributable to the self-supported Co3O4 NTs/Co structure and the interface band structure of Co3O4 NTs and metallic Cu NPs. Furthermore, a possible two-electron reduction mechanism on the selective PEC CO2 reduction to formate at the Cu–Co3O4 NTs was explored. The first electron reduction intermediate, CO2 ads•–, was adsorbed on Cu in the form of Cu–O. W...

Cobalt sulfide nanosheets coated on NiCo2S4 nanotube arrays as electrode materials for high-performance supercapacitors

Abstract: Hierarchical hybrid electrodes were successfully fabricated by electrodeposition of ultrathin cobalt sulfide (CoSx) nanosheets on NiCo2S4 nanotube arrays grown on Ni foam for high-performance supercapacitors. The hierarchical NiCo2S4@CoSx core/shell nanotube arrays exhibit a high areal capacitance (4.74 F cm−2 at a current density of 5 mA cm−2), a good rate capability (2.26 F cm−2 at 50 mA cm−2) and cycle stability (76.1% capacitance retention after 1500 cycles at a high current density of 50 mA cm−2), which are much better than those of NiCo2S4 nanotubes. Such superior electrochemical performance could be attributed to the smart configuration of the two electroactive materials, which can provide more pathways for electron transport and improve the utilization rate of the electrode materials. This effective strategy shows the feasibility of designing and fabricating metal sulfides with core/shell hybrid structures as electrode materials for high-performance supercapacitors.

Visible light-driven photoelectrochemical water splitting on ZnO–TiO 2 heterogeneous nanotube photoanodes

Abstract: TiO2 nanotube arrays (TiO2NTs) with an inner average pore diameter of 80–110 nm and a length of 40 μm were grown on titanium foils by electrochemical anodization in ammonium fluoride–water–ethylene glycol solution. ZnO was grafted on the TiO2 nanotube arrays (ZnO/TiO2NTs) by a chemical bath deposition technique in combination with a pyrolysis process. ZnO/TiO2NTs composite supported on titanium substrate was used as the photoanode for photocatalytic water splitting. Photoelectrochemical characterization shows that grafted ZnO on TiO2NTs efficiently enhanced the photocatalytic water-splitting performance of highly ordered TiO2NT. Such photoanode benefits from the capability of high specific surface and the direct conduction path through the aligned nanotubes. Moreover, the heterojunction at the ZnO/TiO2 interface favors charge separation and reduced the probability of charge recombination. This inexpensive photoanodes prepared free of noble metals, showed enhanced high photocurrent density with good stability, and is a highly promising photoanodes for visible light photocatalytic hydrogen production.

Superior performance asymmetric supercapacitors based on ZnCo2O4@MnO2 core–shell electrode

Abstract: In this study, a hierarchical ZnCo2O4@MnO2 core–shell nanotube arrays electrode was developed by a facile two-step method. The electrode exhibits high specific capacitance of 1981 F g−1 (2.38 F cm−2) at a current density of 5 A g−1 and excellent cycling stability (5000 cycles). Furthermore, a low-cost, high-performance asymmetric supercapacitor (ASC) with ZnCo2O4@MnO2 core–shell nanotube arrays on Ni foam (as positive electrode) and 3D porous α-Fe2O3 on Fe foil (as negative electrode) was successfully designed. The as-designed ASC device with an extended operating voltage window of 1.3 V achieved a specific capacitance of 161 F g−1 at 2.5 mA cm−2 with a maximum energy density of 37.8 W h kg−1 and excellent stability with a capacitance retention of 91% after 5000 cycles. Furthermore, after being charged for dozens of seconds, the ZnCo2O4@MnO2//α-Fe2O3-ASC can easily light up a LED. These fascinating performances indicate that the present ZnCo2O4@MnO2 core–shell nanotube arrays with remarkable electrochemical properties could be considered as potential electrode materials for next generation supercapacitors in high energy density storage systems.

Highly sensitive piezo-resistive graphite nanoplatelet-carbon nanotube hybrids/polydimethylsilicone composites with improved conductive network construction.

Abstract: The constructions of internal conductive network are dependent on microstructures of conductive fillers, determining various electrical performances of composites. Here, we present the advanced graphite nanoplatelet-carbon nanotube hybrids/polydimethylsilicone (GCHs/PDMS) composites with high piezo-resistive performance. GCH particles were synthesized by the catalyst chemical vapor deposition approach. The synthesized GCHs can be well dispersed in the matrix through the mechanical blending process. Due to the exfoliated GNP and aligned CNTs coupling structure, the flexible composite shows an ultralow percolation threshold (0.64 vol %) and high piezo-resistive sensitivity (gauge factor ∼ 10(3) and pressure sensitivity ∼ 0.6 kPa(-1)). Slight motions of finger can be detected and distinguished accurately using the composite film as a typical wearable sensor. These results indicate that designing the internal conductive network could be a reasonable strategy to improve the piezo-resistive performance of composites.

Visible light induced photocatalysis on CdS quantum dots decorated TiO2 nanotube arrays

Abstract: CdS quantum dots (QDs) have been successfully deposited on TiO 2 nanotube arrays (TNTAs) by successive ionic layer adsorption and reaction (SILAR) method for visible-light-driven hydrogen production and organic compound degradation. The composition, morphology and optical property have been characterized by the X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV–vis absorption spectra. The loading amount of CdS can be adjusted by controlling the deposition cycles which demonstrates correspondingly optical behaviors. CdS-TNTAs sample prepared by SILAR deposition with 15 cycles gives the highest hydrogen production rate of 1.89 μmol h −1 cm −2 for 15 mL solutions and the highest degrading rate. Moreover, a transfer mechanism of photo-generated electrons on CdS-TNTAs during the visible-light photocatalytic process is proposed based on the experimental analysis. Furthermore, the prepared sample has good stability and can be more easily reused than the powder catalyst.

A facile one-pot method to synthesize a three-dimensional graphene@carbon nanotube composite as a high-efficiency microwave absorber

Abstract: A novel three-dimensional graphene@carbon nanotube (CNTs) composite has been prepared using a facile one-pot pyrolysis strategy using urea as the carbon source, in which the density and length of CNTs on graphene are rationally tuned by adding an appropriate amount of urea to a precursor mixture. Correspondingly, the density and length of CNTs on graphene have a significant effect on the microwave absorption properties of graphene@CNTs. When most of the graphene surface is clearly covered by the CNTs whose length ranges from 300 to 600 nm, the graphene@CNT composite exhibits excellent microwave absorption properties. The maximum reflection loss value can reach −44.6 dB at 8.6 GHz and the absorption bandwidth with a reflection loss below −10 dB ranges from 7.1 to 10.4 GHz with an addition amount of only 5 wt% graphene@CNTs composite in the paraffin matrix.