Tubular Heterostructure Research Articles

Hierarchical Tubular Architecture Constructed by Vertically Aligned CoS2 -MoS2 Nanosheets for Hydrogen Evolution Electrocatalysis.

Developing efficient electrocatalysts for the hydrogen evolution reaction (HER) is crucial for establishing a sustainable and environmentally friendly energy system, but it is still a challenging issue. Herein, hierarchical tubular-structured CoS2 -MoS2 /C as efficient electrocatalysts are fabricated through a unique metal-organic framework (MOF) mediated self-sacrificial templating. Core-shell structured MoO3 @ZIF-67 nanorods are used both as a precursor and a sacrificial template to form the one-dimensional tubular heterostructure where vertically aligned two-dimensional CoS2 -MoS2 nanosheets are formed on the MOF-derived carbon tube. Trace amounts of noble metals (Pd, Rh, and Ru) are successfully introduced to enhance the electrocatalytic property of the CoS2 -MoS2 /C nanocomposites. The as-synthesized hierarchical tubular heterostructures exhibit excellent HER catalytic performance owing to the merits of the hierarchical hollow architecture with abundantly exposed edges and the uniformly dispersed active sites. Impressively, the optimal Pd-CoS2 -MoS2 /C-600 catalyst delivers a current density of 10 mA cm-2 at a low overpotential of 144 mV and a small Tafel slope of 59.9 mV/dec in 0.5 m H2 SO4 . Overall, this MOF-mediated strategy can be extended to the rational design and synthesis of other hollow heterogeneous catalysts for scalable hydrogen generation.

Construction of Hierarchical Hollow Co9S8/ZnIn2S4 Tubular Heterostructures for Highly Efficient Solar Energy Conversion and Environmental Remediation

AbstractVisible‐light‐responsive hierarchical Co9S8/ZnIn2S4 tubular heterostructures are fabricated by growing 2D ZnIn2S4 nanosheets on 1D hollow Co9S8 nanotubes. This design combines two photoresponsive sulfide semiconductors in a stable heterojunction with a hierarchical hollow tubular structure, improving visible‐light absorption, yielding a large surface area, exposing sufficient catalytically active sites, and promoting the separation and migration of photogenerated charges. The hierarchical nanotubes exhibit excellent photocatalytic H2 evolution and CrVI reduction efficiency. Under visible‐light illumination, the optimized Co9S8/ZnIn2S4 heterostructure provides a remarkable H2 generation rate of 9039 μmol h−1 g−1 without the use of any co‐catalysts and CrVI is completely reduced in 45 min. The Co9S8/ZnIn2S4 heterostructure is stable after multiple photocatalytic cycles.

Construction of Hierarchical Hollow Co9 S8 /ZnIn2 S4 Tubular Heterostructures for Highly Efficient Solar Energy Conversion and Environmental Remediation.

Visible-light-responsive hierarchical Co9 S8 /ZnIn2 S4 tubular heterostructures are fabricated by growing 2D ZnIn2 S4 nanosheets on 1D hollow Co9 S8 nanotubes. This design combines two photoresponsive sulfide semiconductors in a stable heterojunction with a hierarchical hollow tubular structure, improving visible-light absorption, yielding a large surface area, exposing sufficient catalytically active sites, and promoting the separation and migration of photogenerated charges. The hierarchical nanotubes exhibit excellent photocatalytic H2 evolution and CrVI reduction efficiency. Under visible-light illumination, the optimized Co9 S8 /ZnIn2 S4 heterostructure provides a remarkable H2 generation rate of 9039 μmol h-1 g-1 without the use of any co-catalysts and CrVI is completely reduced in 45 min. The Co9 S8 /ZnIn2 S4 heterostructure is stable after multiple photocatalytic cycles.

Construction of CoO/Co‐Cu‐S Hierarchical Tubular Heterostructures for Hybrid Supercapacitors

AbstractHierarchical hollow structures for electrode materials of supercapacitors could enlarge the surface area, accelerate the transport of ions and electrons, and accommodate volume expansion during cycling. Besides, construction of heterostructures would enhance the internal electric fields to regulate the electronic structures. All these features of hierarchical hollow heterostructures are beneficial for promoting the electrochemical properties and stability of electrode materials for high‐performance supercapacitors. Herein, CoO/Co‐Cu‐S hierarchical tubular heterostructures (HTHSs) composed of nanoneedles are prepared by an efficient multi‐step approach. The optimized sample exhibits a high specific capacity of 320 mAh g−1 (2300 F g−1) at 2.0 A g−1 and outstanding cycling stability with 96.5 % of the initial capacity retained after 5000 cycles at 10 A g−1. Moreover, an all‐solid‐state hybrid supercapacitor (HSC) constructed with the CoO/Co‐Cu‐S and actived carbon shows a stable and high energy density of 90.7 Wh kg−1 at a power density of 800 W kg−1.

Construction of CoO/Co-Cu-S Hierarchical Tubular Heterostructures for Hybrid Supercapacitors.

Hierarchical hollow structures for electrode materials of supercapacitors could enlarge the surface area, accelerate the transport of ions and electrons, and accommodate volume expansion during cycling. Besides, construction of heterostructures would enhance the internal electric fields to regulate the electronic structures. All these features of hierarchical hollow heterostructures are beneficial for promoting the electrochemical properties and stability of electrode materials for high-performance supercapacitors. Herein, CoO/Co-Cu-S hierarchical tubular heterostructures (HTHSs) composed of nanoneedles are prepared by an efficient multi-step approach. The optimized sample exhibits a high specific capacity of 320 mAh g-1 (2300 F g-1 ) at 2.0 A g-1 and outstanding cycling stability with 96.5 % of the initial capacity retained after 5000 cycles at 10 A g-1 . Moreover, an all-solid-state hybrid supercapacitor (HSC) constructed with the CoO/Co-Cu-S and actived carbon shows a stable and high energy density of 90.7 Wh kg-1 at a power density of 800 W kg-1 .

Encapsulated MWCNT@MOF-derived In2S3 tubular heterostructures for boosted visible-light-driven degradation of tetracycline

Constructing advanced heterojunction structures is an effective approach to improve light utility and enhance photogenerated charge separation and transfer for solar energy conversion. Herein, we reported a MWCNT@MOF-derived In2S3 hollow tube heterostructure via facile MOF sulfidation process, significantly boosting its photocatalytic degradation performance of tetracycline (TC) under visible light irradiation. The MWCNT bonds to the In2S3 hollow tube strongly to construct an effective heterojunction, as illustrated in TEM and Raman spectroscopy. The 0.3%-MWCNT@MOF-derived In2S3 exhibited the highest photocatalytic activity for visible-light-driven TC degradation, achieving ˜100% degradation efficiency, with its apparent reaction rate constants 3–5 times higher than that of the pure MOF-derived hollow In2S3 and traditional In2S3 bulk. The boosted visible-light-driven degradation efficiency was attributed to the synergy between electron acceptor of MWCNTs for enhanced separation of charge carriers and active center of MOF-derived In2S3 hollow tube with shorter transfer distance of charge carriers, which not only promotes the carrier transfer and inhibits the recombination rate effectively, but also improves the visible light response. Such MOF-derived visible-light-active heterostructures thus provide a novel insight into the development of highly efficient photocatalyst for a wide usage.

Coaxial-cable hierarchical tubular MnO2@Fe3O4@C heterostructures as advanced anodes for lithium-ion batteries

Nanostructured manganese oxides have been regarded as promising anodes for lithium-ion batteries (LIBs) due to their high specific capacity, environmental friendliness and low cost. However, as conversion-type electrodes, their scalable utilization is hindered by intrinsically low reaction kinetics, large volume variation and high polarization. Herein, a coaxial-cable tubular heterostructure composed of a hollow carbon skeleton, Fe3O4 nanoparticles and ultrathin MnO2 nanosheets from inside out, donated as MnO2@Fe3O4@C, is synthesized via a facile two-step hydrothermal process. The unique design integrates conductive carbon and nanostructured MnO2 and Fe3O4 into a one-dimensional (1D) hierarchically open architecture, which provides abundant electrode–electrolyte contact areas, favorable heterointerfaces and ultrafast electron/ion pathways. Benefiting from these features, the MnO2@Fe3O4@C anode exhibits a high reversible capacity of 946 mAh g−1 at 200 mA g−1 after 160 cycles, and excellent cyclability with a specific capacity of 845 mAh g−1 at 500 mA g−1 after 600 cycles. This work might provide an insightful guideline for the design of novel electrode materials.

Construction of MoS2/C Hierarchical Tubular Heterostructures for High-Performance Sodium Ion Batteries.

Molybdenum disulfide (MoS2) has been considered to be a promising anode material for sodium ion batteries (SIBs), because of its high capacity and graphene-like layered structure. However, irreversible conversion reaction during the sodiation/desodiation process is a major problem that must be overcome before its practical applications. In this work, MoS2/amorphous carbon (C) microtubes (MTs) composed of heterostructured MoS2/C nanosheets have been developed via a simple template method. The existence of MoS2/C heterointerface plays a key role in achieving high and stable performance by stabilizing the reaction products Mo and sulfide phases, providing fast electronic and Na+ ions diffusion mobility, and alleviating the volume change. MoS2/C MTs exhibit a high reversible specific capacity of 563.5 mA h g-1 at 0.2 A g-1, good rate performance (520.5, 489.4, 452.9, 425.1, and 401.3 mA h g-1 at 0.5, 1.0, 2.0, 5.0, and 10.0 A g-1, respectively), and excellent cycling stability (484.9 mA h g-1 at 2.0 A g-1 after 1500 cycles).

Construction of ZnIn2S4-In2O3 Hierarchical Tubular Heterostructures for Efficient CO2 Photoreduction.

We demonstrate the rational design and construction of sandwich-like ZnIn2S4-In2O3 hierarchical tubular heterostructures by growing ZnIn2S4 nanosheets on both inner and outer surfaces of In2O3 microtubes as photocatalysts for efficient CO2 photoreduction. The unique design integrates In2O3 and ZnIn2S4 into hierarchical one-dimensional (1D) open architectures with double-heterojunction shells and ultrathin two-dimensional (2D) nanosheet subunits. This design accelerates the separation and transfer of photogenerated charges, offers large surface area for CO2 adsorption, and exposes abundant active sites for surface catalysis. Benefiting from the structural and compositional merits, the optimized ZnIn2S4-In2O3 photocatalyst exhibits outstanding performance for reductive CO2 deoxygenation with considerable CO generation rate (3075 μmol h-1 g-1) and high stability.

A 1D conical nanotubular TiO2/CdS heterostructure with superior photon-to-electron conversion.

Herein, a new strategy to efficiently harvest photons in solar cells is presented. A solar cell heterostructure is put forward, based on a 1D conical TiO2 nanotubular scaffold of high aspect ratio, homogenously coated with a thin few nm layer of CdS light absorber using atomic layer deposition (ALD). For the first time, a large variety of conical nanotube layers with a huge span of aspect ratios was utilized and ALD was used for the preparation of a uniform CdS coating within the entire high surface area of the TiO2 nanotubes. The resulting 1D conical CdS/TiO2 tubular heterostructure acts as a sink for photons. Due to the multiple light scattering and absorption events within this nanotubular sink, a large portion of photons (nearly 80%) is converted into electrons. It is the combination of the scaffold architecture and the light absorber present on the high surface area as a very thin layer, the optimized charge transport and multiple optical effects that make this heterostructure very promising for the next generation of highly performing solar cells.

Hierarchically assembled tubular shell-core-shell heterostructure of hybrid transition metal chalcogenides for high-performance supercapacitors with ultrahigh cyclability

Pseudo-capacitive transition metal chalcogenides have recently received considerable attention as a promising class of materials for high performance supercapacitors (SCs) due to their superior intrinsic conductivity to circumvent the limitations of corresponding transition metal oxides with relatively poor conductivity. However, the important challenge associated with the utilization of such high-capacitive electrode materials is the development of desirably structured electrode materials, enabling efficient and rapid Faradaic redox reactions and ultra long-term cycling. Here, we propose a hierarchically integrated hybrid transition metal (Cu-Ni) chalcogenide shell-core-shell (HTMC-SCS) tubular heterostructure using a facile bottom-up synthetic approach. The resultant HTMC-SCS electrode exhibits a high volumetric capacitance of 25.9Fcm−3 at a current density of 2mAcm−2. Furthermore, asymmetric SCs based on an HTMC-SCS heterostructured electrode demonstrate a high power density (770mWcm−3) and an energy density (2.63mWhcm−3) as well as an ultrahigh reversible capacity with a capacitance retention of 84% and a long-term cycling stability of over 10,000 cycles. Based on experimental results and density functional theory calculations, these remarkably improved electrochemical features are discussed and explained in terms of the unique combination of the conductive CuS core and active NiS shell materials, hierarchical tubular open geometry with nanoscale inner/outer shell structure, and mechanical stress-mitigating interlayer on shell-core-shell interface, allowing highly reversible and efficient electrochemical redox processes coupled with fast charge transfer kinetics and an electrochemically stable structure.

Smart construction of three-dimensional hierarchical tubular transition metal oxide core/shell heterostructures with high-capacity and long-cycle-life lithium storage

In order to realize new high performance electrodes for lithium-ion batteries (LIBs), the careful design of nanoarchitectures and effective hybridization of active materials are research areas of great interest. Here, we present a simple and highly controllable two-step fabrication technique, followed by a heat treatment process, for the large-scale in situ growth of 3D hierarchical tubular CuO/other metal oxides core/shell heterostructure arrays that are directly grown on Cu foam. As a proof-of-concept demonstration of the application of such 3D hierarchical tubular heterostructure arrays, the prepared tubular CuO/CoO core/shell arrays are investigated as binder- and conductive agent-free anodes for LIBs, exhibiting an impressive capacity of 1364mAhg−1 at a current density of 100mAg−1 after 50 cycles and maintaining 1140mAhg−1 after 1000 cycles at 1.0Ag−1. This excellent electrochemical performance can be attributed to the unique hollow porous architecture consisting of 3D hierarchical tubular core/shell architectures, and the effective hybridization of two electrochemically cohesive active materials. Our work shows that this material has great potential for high-energy and high-power energy storage applications.

The preparation of tubular heterostructures based on titanium dioxide and silica nanotubes and their photocatalytic activity

Tubular heterostructures based on titanium dioxide (TiO2) and silica nanotubes (SNTs) with high photocatalytic activity have been successfully obtained by a simple combination of an electrospinning technique and a solvothermal process. The as-prepared products were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and N2 absorption-desorption experiments. The results confirmed that SNTs with high specific surface area were obtained by efficiently controlling the phase separation and solvent evaporation during the process of electrospinning and calcination, and TiO2 was successfully grown on the SNT substrates. The obtained titanium dioxide/silica nanotubes (TiO2/SNTs) heterostructures showed high photocatalytic activities to degrade Rhodamine 6G because of the formation of heterostructures, which might improve the separation of photogenerated electrons and holes. Furthermore, the TiO2/SNTs heterostructures could be easily recycled without an evident decrease in photocatalytic activity.

Heterostructures with ZnSe Sheaths Coating on Carbon Submicrotubes: Preparation, Characterization, and Formation Mechanism

We designed a feasible one-step process to synthesize heterostructures with inorganic functional materials coating on carbon submicrotubes under a mild condition. The heterostructures of carbon submicrotubes with ZnSe sheaths were successfully synthesized through the polymerization-carbonization-coating process with glucose as both the carbon source and the reductive reagent and ammonia providing an alkaline environment and acting as a soft template. The compositions of the as-obtained product were confirmed by Raman spectroscopy and XRD measurement; the morphology and microstructure were studied by SEM, TEM, and HRTEM. Room-temperature photoluminescence (PL) measurement indicates the as-prepared tubular heterostructures have a sharp and well-resolved NBE emission centered at 436 nm besides the DL emission at 589 nm, which is possibly caused by the interface associated with the combination of carbon submicrotube and ZnSe nanocrystal. One of the advantages in this process is that glucose and ammonia play manifold roles in the formation of the submicroscaled tubular heterostructures. This suggests a new path for convenient synthesis of novel tubular heterostructures with inorganic functional materials attached on carbon tubes. Furthermore, this kind of tubular heterostructure may be an ideal system applied in the fabrication of submicroscaled optoelectronics devices, and investigations on its physical properties could extend the understanding of the structure-property relationships in solids, which are in progress.

Calculation of the Electronic and Thermal Properties of C/BN Nanotubular Heterostructures

Modeling results are presented on the electronic, structural, and thermal properties of a (5,5)C@(17,0)BN-NT tubular heterostructure (a metal-like carbon nanotube inside a dielectric boron nitride nanotube) regarded as a prototype of nanocables. It is shown that the electronic properties of the nanocable remain unchanged up to about 3500 K. The properties of the nanocable are analyzed in comparison with those of a [C60]∞@(17,0)BN-NT peapod, a potential precursor to C/BN nanocables.

Nanoprecipitation resulting from the decomposition of supersaturated solid solutions in the tracks of swift heavy ions

The electron subsystem of a material is strongly excited when swift heavy ions pass through the material. The subsequent relaxation of this excitation results in considerable short-term (<10−9 s) heating of the material in the nanometer vicinity of the projectile trajectory. Nanoprecipitation stimulated by such thermal spikes in supersaturated solid solutions is studied. Nanoprecipitates are shown to form when the temperature in the track reaches a point where the characteristic time of precipitation becomes shorter than the time of cooling of the track. The region of most efficient precipitation may be offset from the track axis. The initial cylindrical nonuniformity of the spatial density of nucleating clusters may cause the formation of nanodimensional tubular heterostructures extended along the trajectory of the heavy ions. The parameters of the system that are the most favorable to the tubular mode of precipitation are found.