Core-shell Nanotubes Research Articles

Facile Synthesis of 3D Cu(OH)2@NiCo-Binary Hydroxide Core–Shell Nanotube Arrays with High Mass Loading for High-Performance Asymmetric Supercapacitors

Facile Synthesis of 3D Cu(OH)₂@NiCo-Binary Hydroxide Core–Shell Nanotube Arrays with High Mass Loading for High-Performance Asymmetric Supercapacitors

Magnetic Properties of a Mixed Spin-1/2 and Spin-7/2 Hexagonal Core-Shell Nanotube

"The magnetic properties and phase diagrams of a hexagonal nanotube with core-shell structure have been examined within the framework of the mean field theory based on the Bogoliubov inequality as well as the Monte Carlo simulation via the Metropolis algorithm. We have studied in detail the influences of the different ex- change couplings and the crystal field on the phase diagrams of the system. This study allowed us to discover the existence of interesting critical phenomena, in particular the compensation behavior. Moreover, we have investigated the behavior of the magne- tizations corresponding to each of the phase diagrams in order to verify the obtained results."

A Safe Separator with Heat‐Dispersing Channels for High‐Rate Lithium‐Ion Batteries

AbstractSeparators are becoming increasingly important in both academic research and industrial production as a means of enhancing the performance of lithium‐ion batteries (LIBs), particularly at a high rate. However, fast charge–discharge processes will produce local heat accumulation, which accelerates the local reaction rate of Li+ to form lithium dendrites. Commercial polyolefin separators fail to tackle the above issue due to inferior thermal stability. Herein, a core–shell structure is proposed to reinforce the polyvinylidene fluoride‐hexafluoropropylene (PVDF‐HFP) matrix through encircling carbon nanotube (CNT) by adherent polydopamine (PDA). The core–shell 3D structure with PDA avoids the short circuits caused by the electrically conductive CNT, and meantime, the CNT serves as an effective radiator for dispersing local heat sources verified through finite element analysis. The composite separator allows LIBs to achieve high Li+ conductivity (0.49 × 10−3 S cm−1) and Li+ transfer number (0.74), resulting in a high capacity retention of 87.35% after 800 cycles at 5C. In particular, the safety is confirmed that the composite separator avoids violent growth of lithium dendrites caused by local heat accumulation through phase‐field simulations. This work suggests a promising approach for the fabrication of core–shell nanotube composite separators for high‐rate and safe LIBs.

Ultralow-Overpotential Acidic Oxygen Evolution Reaction Over Bismuth Telluride-Carbon Nanotube Heterostructure with Organic Framework.

The state-of-the-art iridium and ruthenium oxides-based materials are best known for high efficiency and stability in acidic oxygen evolution reaction (OER). However, the development of economically feasible catalysts for water-splitting technologies is challenging by the requirements of low overpotential, high stability, and resistance of catalysts to dissolution during the acidic oxygen evolution reaction . Herein, an organometallic core-shell heterostructure composed of a carbon nanotube core (CNT) and bismuth telluride (Bi2Te3) shell (denoted as nC-Bi2Te3) is designed and use it as a catalyst for the acidic OER. The proposed catalyst achieves an ultralow overpotential of 160mV at 10mAcm-2 (geometrical), thereby outperforming most of the state-of-the-art precious-metal-based catalysts. The low Tafel slope of 30mVdec-1 and charge transfer resistance (RCT)of 1.5Ω demonstrate its excellent electrocatalytic activity. The morphological and chemical compositions of nC-Bi2Te3 enable the generation of ─OH functional group in the Bi─Te sections formed via a ligand support, which enhances the absorption capacity of H+ ions and increases the intrinsic catalytic activity. The presented insights regarding the material composition-structure relationship can help expand the application scope of high-performance catalysts.

Fast and Sensitive Detection of CO by Bi-MOF-Derived Porous In2O3/Fe2O3 Core-Shell Nanotubes.

In2O3 is an optimal material for sensitive detection of carbon monoxide (CO) gas due to its low resistivity and high catalytic activity. Yet, the gas response dynamics between the CO gas molecules and the surface of In2O3 is limited by its solid structure, resulting in a weak gas response value and sluggish electron transport. Herein, we report a strategy to synthesize porous In2O3/Fe2O3 core-shell nanotubes derived from In/Fe bimetallic organic frameworks. The fabricated porous In2O3/Fe2O3-4 core-shell nanotubes present outstanding gas sensitivities, including a response value 3.8 times (33.7 to 200 ppm CO at 260 °C) higher than that of monometallic-derived In2O3 (8.7), ultrashort response and recovery times (23/76 s) to 200 ppm CO, low detection limit (1 ppm), promising selectivity, and long-term stability. The enhanced sensing mechanisms are clarified by the combination of experiment and first-principles calculations, showing that the synergetic strategy of higher adsorption energy, increased electrical conductivity, higher electron transfer numbers, and larger specific surface area of porous core-shell structures promotes the surface activity and charge transfer efficiency. The present work paves a way to tune gas-sensing materials with special morphologies for the development of high-performance CO sensors.

Magnetic properties and hysteresis loops of mixed spin - (3/2, 1) in core-shell hexagonal nanotube: comparative study of mean-field theory and Monte Carlo simulation

Based on the Ising model, Monte Carlo simulation (MCS) and the Mean- field approximation (MFA) were used to examine the magnetic properties and the phase diagram of a ferrimagnetic mixed-spin (2,3/2) hexagonal Ising nanotube with core-shell structure. The effects of exchange interactions ( ) and the single-ion anisotropies ( ) on the magnetization of the total system, the two sublattices and the hysteresis loops have been discussed in detail. The phase diagrams under the effect of different parameters have been provided. The results demonstrate the emergence of compensation phenomena as well as the second-order phase transitions. Multiple behaviors of hysteresis loop, including single and triple hysteresis loops, were identified as a result of competitions between various parameters.

Insights into the Growth of Ternary WSSe Nanotubes in an Atmospheric CVD Reactor.

The synthesis of complex new nanostructures is challenging but also bears the potential for observing new physiochemical properties and offers unique applications in the long run. High-temperature synthesis of ternary WSe2xS2(1-x) (denoted as WSSe) nanotubes in a pure phase and in substantial quantities is particularly challenging, requiring a unique reactor design and control over several parameters, simultaneously. Here, the growth of WSSe nanotubes with the composition 0 ≤ x < 1 from W18O49 nanowhiskers in an atmospheric chemical vapor deposition (CVD) flow reactor is investigated. The oxide precursor powder is found to be heavily agglomerated, with long nanowhiskers decorating the outer surface of the agglomerates and their core being enriched with oxide microcrystallites. The reaction kinetics with respect to the chalcogen vapors varies substantially between the two kinds of oxide morphologies. Insights into the chemical reactivity and diffusion kinetics of S and Se within W18O49 nanowhishkers and the micro-oxide crystallites were gained through detailed microscopic, spectroscopic analysis of the reaction products and also through density functional theory (DFT) calculations. For safety reasons, the reaction duration was limited to half an hour each. Under these circumstances, the reaction was completed for some 50% of the nanotubes and the other half remained with thick oxide core producing new WOx@WSSe core-shell nanotubes. Furthermore, the selenium reacted rather slowly with the WOx nanowhiskers, whereas the more ionic and smaller sulfur atoms were shown to diffuse and react faster. The yield of the combined hollow and core-shell nanotubes on the periphery of the agglomerated oxide was very high, approaching 100% in parts of the reactor boat. The nanotubes were found to be very thin (∼80% with a diameter <40 nm). The optical properties of the nanotubes were studied, and almost linear bandgap modulation was observed with respect to the selenium content in the nanotubes. This investigation paves the way for further scaling up the synthesis and for a detailed study of the different properties of WSSe nanotubes.

Core-shell metallic nanotube arrays for highly sensitive surface-enhanced Raman scattering (SERS) detection

Here, we demonstrate the application of highly ordered, periodic Ag/Au core-shell triangle nanotube arrays as an ultrasensitive and low-cost surface-enhanced Raman scattering (SERS) substrate for the first time. The arrays of core-shell nanotube, with an outer diameter of 1.5 μm, were fabricated using top-down wafer-scale lithography followed by sequential sputter deposition of Ag and Au. The SERS activity of various combinations of core-shell structures was evaluated. It was found that Ag-core nanotubes overlaid with the Au-shell resulted in the highest Raman intensity, where the enhancement factor for R6G as a probe molecule is determined to be 1.38 × 107. Meanwhile, the limit of detections for R6G and ketoprofen analytes was evaluated to be 10−10 and 10−6 M, respectively. Linear correlations between the SERS signal intensities and logarithmical scale of both analytes in different concentrations were also established, ranging 10−4–10−10 and 10−2–10−6 M for R6G and ketoprofen, respectively. The Raman R6G peak intensity mapping suggests our metal nanotube arrays act as effective plasmonic hotspots and, thus, are useful for SERS sensing applications.

Lightweight Copper–Carbon Nanotube Core–Shell Composite Fiber for Power Cable Application

The substitution of traditional copper power transmission cables with lightweight copper–carbon nanotube (Cu–CNT) composite fibers is critical for reducing the weight, fuel consumption, and CO2 emissions of automobiles and aircrafts. Such a replacement will also allow for lowering the transmission power loss in copper cables resulting in a decrease in coal and gas consumption, and ultimately diminishing the carbon footprint. In this work, we created a lightweight Cu–CNT composite fiber through a multistep scalable process, including spinning, densification, functionalization, and double-layer copper deposition. The characterization and testing of the fabricated fiber included surface morphology, electrical conductivity, mechanical strength, crystallinity, and ampacity (current density). The electrical conductivity of the resultant composite fiber was measured to be 0.5 × 106 S/m with an ampacity of 0.18 × 105 A/cm2. The copper-coated CNT fibers were 16 times lighter and 2.7 times stronger than copper wire, as they revealed a gravimetric density of 0.4 g/cm3 and a mechanical strength of 0.68 GPa, suggesting a great potential in future applications as lightweight power transmission cables.

Direct Synthesis of Dimethyl Ether from CO2 Hydrogenation over Core-Shell Nanotube Bi-Functional Catalyst

Directly synthesising dimethyl ether (DME) from CO2 hydrogenation is a promising technique for efficiently utilising CO2 as a feedstock to produce clean fuel. The main challenges in this process are the low CO2 conversion and DME selectivity of the catalyst and its deactivation over time due to sintering, aggregation, coke formation, and water adsorption. This study aimed to develop a dual-functional, halloysite nanotube-supported CuZnO-PTA catalyst with a core-shell structure and investigate the effects of the active site mass ratio CuZnO/PTA on CO2 conversion and DME selectivity. A dual-functional core-shell mesopores halloysite nanotube (HNT) catalyst was developed, and both active sites were co-hosted on one support. The co-impregnation method was used to synthesise CuZnO and 12-phosphotungstic acids (PTA) that were then supported by a mesoporous core-shell (HNT). BET surface area, N2 physisorption, FE-SEM, SEM, XRD, H2-TPR, and NH3-TPD of the core-shell catalyst characterised physio-chemical properties of the prepared hybrid catalyst. The experimental results showed that the synthesised CuZn-PTA@HNT core-shell bifunctional catalyst was promising; the CO2 conversion was almost the same for all four catalysts, with an average of 22.17%, while the DME selectivity reached 68.9%. Furthermore, the effect of both active sites on the hybrid catalyst was studied, and the metal Cu wt% mass ratio loading was not significant. In contrast, the PTA acid sites positively affected DME selectivity; they also showed an excellent tolerance towards the water generated in the methanol dehydration reaction. In addition, the effect of the temperature and reusability of the CZ-PTA@HNT catalyst has also been investigated, and the results show that increasing the temperature improves CO2 conversion but decreases DME selectivity. A temperature of less than 305 °C is a good compromise between CO2 conversion and DME selectivity, and the catalyst also showed good stability and continuous activity/stability over five consecutive cycles. In conclusion, this study presents a novel approach of using a core-shell halloysite nanotube-supported CuZnO-PTA catalyst to directly synthesise dimethyl ether (DME) from CO2 hydrogenation which exhibits promising results in terms of CO2 conversion and DME selectivity.

Copper Foam-Supported CuxO@Fe2O3 Core–Shell Nanotubes: An Efficient Ozonation Catalyst for Degradation of Organic Pollutants

Copper foam (CF)-supported CuxO@Fe2O3 core–shell nanotubes (CF/CuxO@Fe2O3 NTs) were synthesized as a hybrid catalyst for heterogeneous catalytic ozonation (HCO). The hybrid catalyst exhibits high activity and excellent stability for the HCO of organic pollutants. The total organic carbon removal rates of methyl orange, ibuprofen, and nitrobenzene via HCO were 89, 82, and 88%, respectively, which are over 2 times higher than the corresponding values obtained without the catalyst. The hybrid catalyst also displays wide pH operation range, low metal leaching, easy separation from treated water, and excellent recyclability. We prove that large amounts of Lewis acid sites with medium acidity are created at the CuxO/Fe2O3 interface due to the synergic effect of CuxO and Fe2O3. These medium acid sites are the main active centers for the production of free hydroxyl radicals (•OH) and superoxide radicals (O2•– or HO2•) in neutral solution. Moreover, the 3D porous framework of the catalyst enables easy dispersion in and separation from water. This work develops a new strategy to design HCO catalysts by combining strong and weak Lewis acid oxides and also opens a new avenue for developing HCO catalysts on a 3D porous framework.

Construction of hierarchical NiCoSe@CoS core–shell nanotube arrays for high-performance hybrid supercapacitor

In this work, core–shell [email protected] nanotube arrays directly grown on nickel foam were synthesized via two-step hydrothermal method combined with cyclic voltammetry electrodeposition. In such heterostructures, NiCoSe nanotubes as the core were wrapped by interconnected CoS nanosheets as the shell. Results showed that the obtained [email protected] nanotube arrays formed a conductive 3D network by growing CoS nanosheets on the surface of the NiCoSe nanotubes, which increased electroactive sites, shortened ion diffusion pathways, and thus enhanced charge storage. The unique core–shell heterostructures improved the structural stability and accelerated the electrode reaction kinetics of the nanotube arrays. Compared with the single-phase CoS nanosheets and NiCoSe nanotube arrays, the [email protected] nanotube arrays as electrodes demonstrated enhanced areal capacitance (3.28 and 2.22 F cm−2 at 3 and 30 mA cm−2, respectively) and cyclic stability (capacity retention rate of 93 % after 5000 cycles at 3 mA cm−2). Furthermore, the [email protected] nanotube arrays were used as the positive electrode to assemble hybrid supercapacitor devices with carbon nanotubes as the negative electrode. The fabricated device can deliver an energy density of 36.3 Wh kg−1 at a power density of 801.7 W kg−1 with long-term cycling stability, which indicates that the [email protected] nanotube arrays have a greatly practical application value in supercapacitor devices.

A homologous N/P-codoped carbon strategy to streamline nanostructured MnO/C and carbon toward boosted lithium-ion capacitors

Lithium-ion capacitors (LICs) are drawing increasingly attention owing to their attractive virtues of high energy/power density and long lifetime. However, overcoming the kinetic mismatch of battery-type anodes and capacitor-type cathodes remains an intractable challenge. In this work, we report a homologous N/P-codoped carbon (NPC) strategy to boost lithium-ion capacitors based on nanostructured MnO/C anodes and carbon cathodes. A controllable phytic acid-assisted polymerization method based on the MnO2 precursors is developed to streamline the fabrication of MnO/NPC core-shell nanowires and NPC nanotubes (NPCT). The NPC is of profound benefit for regulating the surface functionality, porosity, and electron transfer kinetics, which greatly minimizes the kinetic mismatch. The battery-type MnO/NPC anode retains a large capacity of 314 mAh g−1 at a high-rate of 5 A g−1, while the capacitor-type NPCT cathode delivers a 110 mAh g−1 at 0.1 A g−1. The as-built LICs exhibit a high energy density of 145 Wh kg−1, a high power density of 10 kW kg−1, and good cycling lifespan. The present study will enlighten the significance of N/P dual-doping in designing high-performance LICs.

Highly efficient and durable electrochemical hydrogen evolution reaction based on composition/shape controlled CuTi@Pt core-shell nanotubes in acidic media

High-quality electrocatalysts for hydrogen evolution reactions, which have long-term stability and high efficiency, are a major challenge. Enhancing electrocatalytic efficiency can be achieved by creating alloys, designing core–shell structures, and controlling shapes. Herein, we demonstrate an elevated performance CuTi@Pt alloy catalyst with a one-dimensional nanotube structure through a galvanic replacement reaction. While the Pt/Cu atomic ratio and the wall thickness of the nanotube are carefully tuned, the CuTi@Pt alloy phase and tube structure are consequentially controlled. A systematic investigation is then conducted into the differences in composition and shape that impact the activity and durability. The optimized CuTi@Pt nanotube catalyst shows significant enhancements in the HER activity (1.12-fold decrease in Tafel compared to the commercial Pt/C) and the durability (remains unchanged after 24 h).

Luminescence properties, and anti-counterfeiting application of one-dimensional electrospun Y2Ti2O7:Ho/Yb nanostructures

One-dimensional Y2Ti2O7:Ho/Yb nanostructures, including nanowires, nanotubes, and wire-in-tube architectures, were fabricated via a simple electrospinning technique using a single-nozzle system. The diameters of Y2Ti2O7:Ho/Yb nanowires are between 180 and 200 nm. The Y2Ti2O7:Ho/Yb nanotubes have an outer diameter of 180 nm and a wall thickness of 30–40 nm. In the Y2Ti2O7:Ho/Yb wire-in-tube architectures, the outer diameter of tubes, wall thickness of tubes, and diameter of wire are 180–190, 25–30, and 30–35 nm, respectively. The electrospinning process's environment humidity considerably influences the one-dimensional Y2Ti2O7:Ho/Yb nanostructure morphology. Further, the upconversion luminescence properties and temperature sensitivity of the one-dimensional Y2Ti2O7:Ho/Yb nanostructure were investigated compared with that of the Y2Ti2O7: Ho/Yb bulk prepared via solid-state reactions. Furthermore, to realize their dual-mode anticounterfeiting function, the Y2Ti2O7:Ho/Yb nanotubes were coated with a rare-earth nitrate (RE (NO3)3) using a homogeneous precipitation technique to obtain core-shell structure nanotubes of Y2Ti2O7:1 mol%Ho/20 mol%Yb @ Y2O3:10 mol%Eu.

Refractive index sensing performance of a bimetallic core-shell nanotube

The sensing performance of a bimetallic core-shell nanotube is studied theoretically based on the theory of TE-polarized light scattering by a multilayer infinite cylinder. The nanotube consists of a metallic core and a metallic shell with the analyte is inserted between the core and the shell. It is found that the absorption efficiency spectra of a bimetallic core-shell nanotube exhibit three resonance peaks correspond to the dipole, quadrupole and sextupole mode. As the refractive index of the analyte increased from n2 = 1.33 to n2 = 1.45, these resonance peaks are linearly redshifted. By calculating the figure of merit (FOM), it is found that the high sensing performance with FOM > 100 could be achieved. The dipole mode exhibits a higher sensing performance as compared to the other modes. Finally, the sensing performance is very sensitive to variations of the geometrical parameter and the background medium of the nanotube.

Space-controllable TiO2@IrO2 core-shell nanotube array as a bio-interface electrode

This study develops a wet chemical approach to fabricate space-controllable TiO2@IrO2 core@shell nanotube arrays. The process begins with the space-controlling anodization of the TiO2 nanotube array, followed by a chemical bath deposition of IrO2. IrO2 uniformly covers the nanotubular TiO2 with a thickness range of 8– 15 nm. Charge storage capacity (CSC) and electrochemical impedance spectroscopy (EIS) are performed to evaluate the TiO2@IrO2 core-shell nanotube array as an electrode for neural activity application. Electron microscopy images confirm the formation of uniform IrO2 films on both inner and outer nanotube surfaces. An X-ray diffraction pattern shows a good crystallinity of the TiO2@IrO2 core-shell nanotube array. The TiO2@IrO2 core-shell nanotube array presents a large charge storage capacity of 42.84 mC/cm2 attributed to the high-aspect-ratio tubular nanostructure with a conformal IrO2 deposition. Additionally, the TiO2@IrO2 core-shell nanotube array exhibits stability, durability, and good biocompatibility.

Highly Efficient and Durable Electrochemical Hydrogen Evolution Reaction Based on Composition/Shape Controlled Cuti@Pt Core-Shell Nanotubes in Acidic Media

Highly Efficient and Durable Electrochemical Hydrogen Evolution Reaction Based on Composition/Shape Controlled Cuti@Pt Core-Shell Nanotubes in Acidic Media

Hierarchical pipe cactus-like Ni/NiCo-LDH core–shell nanotube networks as a self-supported battery-type electrode for supercapacitors with high volumetric energy density

An ultrathin 3D NiCo-LDH@Ni-NTNW electrode for supercapacitors demonstrates an ultrahigh volumetric capacity and excellent cycling stability. The assembled hybrid supercapacitor delivers a record-high volumetric energy density of 14.7 mWh cm−3.

Construction of Hierarchical NiCoSe@CoS Core–Shell Nanotube Arrays for High-Performance Hybrid Supercapacitor

Construction of Hierarchical NiCoSe@CoS Core–Shell Nanotube Arrays for High-Performance Hybrid Supercapacitor