Core-shell Nanotube Arrays Research Articles

Hexagonal prism-like hierarchical Co9S8@Ni(OH)2core–shell nanotubes on carbon fibers for high-performance asymmetric supercapacitors

In this work, novel hierarchical cobalt sulfide@nickel hydroxide [Co9S8@Ni(OH)2] core–shell nanotube arrays supported on carbon fibers have been designed logically and synthesized for use as supercapacitors.

Constructing polypyrrole/aligned carbon nanotubes composite materials as electrodes for high-performance supercapacitors

Polypyrrole/aligned carbon nanotubes (PPy/ACNTs) core-shell nanotube arrays on metal foil have been fabricated through an electrochemical method. The as-prepared PPy/ACNTs electrode materials with novel nanostructure, which is very conducive to the transmission of electrons and ions, possess greatly improved electrochemical performance. The specific capacitances of PPy/ACNTs electrode materials can reach 505F/g (vs. the both mass of PPy and ACNTs) in three-electrode system. In two-electrode system, the specific capacitances of the PPy/ACNTs electrode materials can reach 456F/g (vs. the both mass of PPy and ACNTs). The PPy/ACNTs electrode materials also exhibit greatly improved rate capability and superior cycling performance.

Aligned MoOx/MoS2 Core–Shell Nanotubular Structures with a High Density of Reactive Sites Based on Self‐Ordered Anodic Molybdenum Oxide Nanotubes

AbstractThe present work demonstrates the self‐organized formation of anodic molybdenum oxide nanotube arrays. The amorphous tubes can be crystallized to MoO2 or MoO3 and be converted fully or partially into molybdenum sulfide. Vertically aligned MoOx/MoS2 nanotubes can be formed when, under optimized conditions, defined MoS2 sheets form in a layer by layer arrangement that provide a high density of reactive stacking misalignments (defects). These core–shell nanotube arrays consist of a conductive suboxide core and a functional high defect density MoS2 coating. Such structures are highly promising for applications in electrocatalysis (hydrogen evolution) or ion insertion devices.

Aligned MoOx /MoS2 Core-Shell Nanotubular Structures with a High Density of Reactive Sites Based on Self-Ordered Anodic Molybdenum Oxide Nanotubes.

The present work demonstrates the self-organized formation of anodic molybdenum oxide nanotube arrays. The amorphous tubes can be crystallized to MoO2 or MoO3 and be converted fully or partially into molybdenum sulfide. Vertically aligned MoOx /MoS2 nanotubes can be formed when, under optimized conditions, defined MoS2 sheets form in a layer by layer arrangement that provide a high density of reactive stacking misalignments (defects). These core-shell nanotube arrays consist of a conductive suboxide core and a functional high defect density MoS2 coating. Such structures are highly promising for applications in electrocatalysis (hydrogen evolution) or ion insertion devices.

Construction of a Hierarchical NiCo2S4@PPy Core-Shell Heterostructure Nanotube Array on Ni Foam for a High-Performance Asymmetric Supercapacitor.

In this paper, a hierarchical NiCo2S4@polypyrrole core-shell heterostructure nanotube array on Ni foam (NiCo2S4@PPy/NF) was successfully developed as a bind-free electrode for supercapacitors. NiCo2S4@PPy-50/NF obtained under 50 s PPy electrodeposition shows a low charge-transfer resistance (0.31 Ω) and a high area specific capacitance of 9.781 F/cm(2) at a current density of 5 mA/cm(2), which is two times higher than that of pristine NiCo2S4/NF (4.255 F/cm(2)). Furthermore, an asymmetric supercapacitor was assembled using NiCo2S4@PPy-50/NF as positive electrode and activated carbon (AC) as negative electrode. The resulting NiCo2S4@PPy-50/NF//AC device exhibits a high energy density of 34.62 Wh/kg at a power density of 120.19 W/kg with good cycling performance (80.64% of the initial capacitance retention at 50 mA/cm(2) over 2500 cycles). The superior electrochemical performance can be attributed to the combined contribution of both component and unique core-shell heterostructure. The results demonstrate that the NiCo2S4@PPy-50 core-shell heterostructure nanotube array is promising as electrode material for supercapacitors in energy storage.

Controllable synthesis of hierarchical NiCo2S4@Ni3S2 core–shell nanotube arrays with excellent electrochemical performance for aqueous asymmetric supercapacitors

Unique NiCo2S4@Ni3S2 core–shell nanotube arrays with a hierarchical structure, as promising positive electrodes for supercapacitors, were designed and synthesized on the surface of Ni foam via a hydrothermal reaction and electrodeposition method.

NiCo2S4/Ni(OH)2 core-shell heterostructured nanotube arrays on carbon-fabric as high-performance pseudocapacitor electrodes

High-performance supercapacitor electrodes with a core-shell heterostructure of carbon-fabric/NiCo2S4/Ni(OH)2 are rationally designed. The NiCo2S4 nanotube core synthesized by two step hydrothermal methods has a diameter of about 120nm and a thickness of about 25nm. The Ni(OH)2 shell prepared by electrochemical deposition method is made up by the small Ni(OH)2 ultrathin sheets. With this design and method, high specific capacitance of 2700F/g at a current density of 1mA/cm2 is found from NiCo2S4/Ni(OH)2 heterostructured arrays. These samples show energy density of 120Wh/kg and power density of 0.4kW/kg at a current density of 1mA/cm2, and good cycle stability with 78% capacitance retention after 2000 circles.

Fabrication of Highly Ordered and Well‐Aligned PbTiO3/TiN Core–Shell Nanotube Arrays

Highly ordered and well-aligned PbTiO3/TiN core-shell nanotubes are fabricated via an anodic aluminum oxide templating route followed by TiN and TiO2 atomic layer deposition deposition and a subsequent PbO vapor reaction. PbTiO3/TiN nanotubes keep their original shape after the vapor phase reaction, and they display well-defined piezoresponse hysteresis curves with remnant piezoresponse of 38 pm V(-1) .

Copper–silicon core–shell nanotube arrays for free-standing lithium ion battery anodes

A free-standing and binder-free ultrathin (around 10 μm) 1D structured anode was reported, which was the first time copper–silicon core–shell nanotube arrays were fabricated using silicon nanowire arrays as the template. Within this design, cone-shaped copper nanotube arrays act as both the supporter of amorphous silicon and the current collector for the electrode.

From GaN to ZnGa2O4 through a Low-Temperature Process: Nanotube and Heterostructure Arrays

We demonstrate a method to synthesize GaN-ZnGa2O4 core-shell nanowire and ZnGa2O4 nanotube arrays by a low-temperature hydrothermal process using GaN nanowires as templates. Transmission electron microscopy and X-ray photoelectron spectroscopy results show that a ZnGa2O4 shell forms on the surface of GaN nanowires and that the shell thickness is controlled by the time of the hydrothermal process and thus the concentration of Zn ions in the solution. Furthermore, ZnGa2O4 nanotube arrays were obtained by depleting the GaN core from GaN-ZnGa2O4 core-shell nanowire arrays during the reaction and subsequent etching with HCl. The GaN-ZnGa2O4 core-shell nanowires exhibit photoluminescence peaks centered at 2.60 and 2.90 eV attributed to the ZnGa2O4 shell, as well as peaks centered at 3.35 and 3.50 eV corresponding to the GaN core. We also demonstrate the synthesis of GaN-ZnGa2O4 heterojunction nanowires by a selective formation process as a simple route toward development of heterojunction nanodevices for optoelectronic applications.

Fabrication of ZnO@TiO2 Core-Shell Nanotube Arrays as Three-Dimensional Anode Material for Lithium Ion Batteries

Fabrication of ZnO@TiO2 Core-Shell Nanotube Arrays as Three-Dimensional Anode Material for Lithium Ion Batteries

Electrochemical synthesis of ZnO/CdTe core-shell nanotube arrays for enhanced photoelectrochemical properties

ZnO/CdTe core–shell nanotube arrays are controllablly synthesized using a simple two-step electrochemical deposition strategy in this paper. The as-prepared ZnO/CdTe core–shell nanotube arrays are found to exhibit significantly enhanced photocurrent density for water splitting as compared to the ZnO nanorod arrays. This is mainly due to the lower the band gap or the lower density of oxygen vacancies and other defects states. Furthermore, the effect of CdTe loading on the photoelectrochemical performances of ZnO/CdTe core–shell nanotube arrays was also investigated.

CdSe/CdS quantum dots co-sensitized TiO2 nanotube array photoelectrode for highly efficient solar cells

In this work, we designed and fabricated a novel one-dimensional CdSe/CdS@TiO2 core–shell nanotube array for quantum dots co-sensitized solar cells (QDSSCs) application. The three-component core–shell nanotube array structure was formed cascade by coating CdS nanoparticles with a successive ionic layer adsorption and reaction process and a thin CdSe layer by chemical bath deposition onto the vertical TiO2 nanotube arrays (TNAs), which enhanced the optical absorption in the visible region and presented an stepwise band-edge level structure to improve the charge separation. Under optimum conditions, the CdS/CdSe co-sensitized QDSSC demonstrated a power conversion efficiency (PCE) of 2.40% under 100mW/cm2 illumination of simulate sunlight. Furthermore, an improved QDSSC with a PCE up to 2.74% was obtained by sealed annealing of TNAs, due to the transformation of thin and smooth nanotube to thick and rough particle nanotube.

Porous Ni@Pt Core‐Shell Nanotube Array Electrocatalyst with High Activity and Stability for Methanol Oxidation

Bimetallic core-shell nanostructures are emerging as more important materials than monometallic nanostructures, and have much more interesting potential applications in various fields, including catalysis and electronics. In this work, we demonstrate the facile synthesis of core-shell nanotube array catalysts consisting of Pt thin layers as the shells and Ni nanotubes as the cores. The porous Ni@Pt core-shell nanotube arrays were fabricated by ZnO nanorod-array template-assisted electrodeposition, and they represent a new class of nanostructures with a high electrochemically active surface area of 50.08 m(2) (g Pt)(-1), which is close to the value of 59.44 m(2) (g Pt)(-1) for commercial Pt/C catalysts. The porous Ni@Pt core-shell nanotube arrays also show markedly enhanced electrocatalytic activity and stability for methanol oxidation compared with the commercial Pt/C catalysts. The attractive performances exhibited by these prepared porous Ni@Pt core-shell nanotube arrays make them promising candidates as future high-performance catalysts for methanol electrooxidation. The facile method described herein is suitable for large-scale, low-cost production, and significantly lowers the Pt loading, and thus, the cost of the catalysts.

A novel semiconductor-sensitized solar cell based on P3HT@CdS@TiO2 core-shell nanotube array

In this paper, a novel semiconductor-sensitized solar cell with the photoanode based on poly (3-hexylthiophene) (P3HT)@CdS@TiO2 nanotube array was fabricated. Vertically oriented TiO2 nanotube arrays were prepared by a sol–gel based method using ZnO nanorod arrays as sacrificing template. CdS nanocrystals and a thin P3HT layer were electrodeposited onto the wall of TiO2 nanotube to prepare the photoanode of the semiconductor-sensitized solar cell. It has been demonstrated that the coating of P3HT on the surface of the CdS@TiO2 core-shell nanotube arrays could largely improve the photovoltaic performance of the solar cell. A power conversion efficiency of 1.16% was obtained with this type of solar cell.

Fabrication of Poly(3-hexylthiophene)/CdS/ZnO Core–Shell Nanotube Array for Semiconductor-Sensitized Solar Cell

In this article, we designed and fabricated a novel semiconductor-sensitized solar cell using a poly(3-hexylthiophene) (P3HT)/CdS/ZnO core–shell nanotube array as the photoanode. A facile sequent electrodeposition process was employed to prepare the photoanode. The one-dimensional three-component core–shell ordered nanoarray structure was formed by electrodepositing CdS nanoparticles and a thin P3HT layer onto the walls of ZnO nanotubes, which enhanced the optical absorption in the visible region and presented an interface between n-type CdS and p-type P3HT to improve the charge separation. An energy conversion efficiency up to 1.28% was obtained with the designed nanostructured solar cell based on the P3HT/CdS/ZnO nanotube array.

Synthesis and magnetic characterization of Co-NiO-Ni core-shell nanotube arrays

Well-aligned Ni and Co-NiO-Ni core-shell nanotube arrays with an average outer diameter of about 200 nm have been synthesized in a porous anodic aluminum oxide (AAO) template by the direct electro-deposition method. The result shows that the nanotubes were polycrystalline phase. Angular dependent coercivity Hc(θ) indicates that the magnetization reversal mechanisms are mainly dominated by the “curling mode” for Ni nanotubes, while a transition from curling to transverse is observed in Co-NiO-Ni core-shell nanotubes at a large angle. A sharp increase in saturated magnetization (Ms) of Ni and Co-NiO-Ni core-shell nanotubes at 5 K was observed, due to dominance of the surface effect. Besides, the existed superparamagnetic nanoparticles also resulted in the increase of Ms for both cases. These structures have potential applications in the novel spintronics device, ultrasmall magnetic media, and other nanodevices.

Effect of Size-Dependent Thermal Instability on Synthesis of Zn2SiO4-SiO x Core–Shell Nanotube Arrays and Their Cathodoluminescence Properties

Vertically aligned Zn2SiO4-SiOx(x < 2) core–shell nanotube arrays consisting of Zn2SiO4-nanoparticle chains encapsulated into SiOx nanotubes and SiOx-coated Zn2SiO4 coaxial nanotubes were synthesized via one-step thermal annealing process using ZnO nanowire (ZNW) arrays as templates. The appearance of different nanotube morphologies was due to size-dependent thermal instability and specific melting of ZNWs. With an increase in ZNW diameter, the formation mechanism changed from decomposition of “etching” to Rayleigh instability and then to Kirkendall effect, consequently resulting in polycrystalline Zn2SiO4-SiOx coaxial nanotubes, single-crystalline Zn2SiO4-nanoparticle-chain-embedded SiOx nanotubes, and single-crystalline Zn2SiO4-SiOx coaxial nanotubes. The difference in spatially resolved optical properties related to a particular morphology was efficiently documented by means of cathodoluminescence (CL) spectroscopy using a middle-ultraviolet emission at 310 nm from the Zn2SiO4 phase.

Synthesis and optical properties of ZnO–ZnS core-shell nanotube arrays

Heterostructured ZnO–ZnS core-shell nanotube arrays with the diameters of 50–80nm and lengths up to 1μm were synthesized by a two-step chemical reaction. First, the ZnO layer was grown by atomic-layer deposition. It was found that the preferred growth orientation was strongly dependent on the substrate temperature. After sulfuration conversion from arrayed ZnO nanorods, the ZnS–ZnO composite arrays can be successfully prepared, as evidenced from transmission electron microscopy. This confirms that the ZnO–ZnS core-shell nanotube-arrayed structure has been fabricated. X-ray photoelectron spectroscopy analysis indicates that the binding energy of S 2p is the same as that of bulk single-crystal ZnS and that the Zn 2p3∕2 peak is shifted about 0.5eV due to the formation of Zn–S bonds. Photoluminescence shows the relative-intensity ratio of ultraviolet emission (IUV) to deep-level emission (IDLE) for ZnO∕ZnS core-shell nanotubes can be enhanced to be nine times that of original ZnO nanotubes.