Showing papers on "Nanotube published in 2017"

Hierarchical Porous O-doped g-C3N4 with Enhanced Photocatalytic CO2 Reduction Activity

Abstract: Artificial photosynthesis of hydrocarbon fuels by utilizing solar energy and CO2 is considered as a potential route for solving ever-increasing energy crisis and greenhouse effect. Herein, hierarchical porous O-doped graphitic carbon nitride (g-C3 N4 ) nanotubes (OCN-Tube) are prepared via successive thermal oxidation exfoliation and curling-condensation of bulk g-C3 N4 . The as-prepared OCN-Tube exhibits hierarchically porous structures, which consist of interconnected multiwalled nanotubes with uniform diameters of 20-30 nm. The hierarchical OCN-Tube shows excellent photocatalytic CO2 reduction performance under visible light, with methanol evolution rate of 0.88 µmol g-1 h-1 , which is five times higher than bulk g-C3 N4 (0.17 µmol g-1 h-1 ). The enhanced photocatalytic activity of OCN-Tube is ascribed to the hierarchical nanotube structure and O-doping effect. The hierarchical nanotube structure endows OCN-Tube with higher specific surface area, greater light utilization efficiency, and improved molecular diffusion kinetics, due to the more exposed active edges and multiple light reflection/scattering channels. The O-doping optimizes the band structure of g-C3 N4 , resulting in narrower bandgap, greater CO2 affinity, and uptake capacity as well as higher separation efficiency of photogenerated charge carriers. This work provides a novel strategy to design hierarchical g-C3 N4 nanostructures, which can be used as promising photocatalyst for solar energy conversion.

Enhanced water permeability and tunable ion selectivity in subnanometer carbon nanotube porins.

Abstract: Fast water transport through carbon nanotube pores has raised the possibility to use them in the next generation of water treatment technologies. We report that water permeability in 0.8-nanometer-diameter carbon nanotube porins (CNTPs), which confine water down to a single-file chain, exceeds that of biological water transporters and of wider CNT pores by an order of magnitude. Intermolecular hydrogen-bond rearrangement, required for entry into the nanotube, dominates the energy barrier and can be manipulated to enhance water transport rates. CNTPs block anion transport, even at salinities that exceed seawater levels, and their ion selectivity can be tuned to configure them into switchable ionic diodes. These properties make CNTPs a promising material for developing membrane separation technologies.

A High‐Efficiency Sulfur/Carbon Composite Based on 3D Graphene Nanosheet@Carbon Nanotube Matrix as Cathode for Lithium–Sulfur Battery

Abstract: Carbon materials have attracted extensive attention as the host materials of sulfur for lithium–sulfur battery, especially those with 3D architectural structure. Here, a novel 3D graphene nanosheet–carbon nanotube (GN–CNT) matrix is obtained through a simple one-pot pyrolysis process. The length and density of CNTs can be readily tuned by altering the additive amount of carbon source (urea). Specifically, CNTs are in situ introduced onto the surface of the graphene nanosheets (GN) and show a stable covalent interaction with GN. Besides, in the GN–CNT matrix, cobalt nanoparticles with different diameters exist as being wrapped in the top of CNTs or scattering on the GN surface, and abundant heteroatoms (N, O) are detected, both of which can help in immobilizing sulfur species. Such a rationally designed 3D GN–CNT matrix makes much more sense in enhancing the electrochemical performance of the sulfur cathode for rapid charge transfer and favorable electrolyte infiltration. Moreover, the presence of dispersed cobalt nanoparticles is beneficial for trapping lithium polysulfides by strong chemical interaction, and facilitating the mutual transformation between the high-order polysulfides and low-order ones. As a result, the S/GN–CNT composite presents a high sulfur utilization and large capacity on the basis of the S/GN–CNT composite as active material.

Fe2O3 Nanoneedles on Ultrafine Nickel Nanotube Arrays as Efficient Anode for High-Performance Asymmetric Supercapacitors

Abstract: High performance of electrochemical energy storage devices depends on the smart structure engineering of electrodes, including the tailored nanoarchitectures of current collectors and subtle hybridization of active materials. To improve the anode supercapacitive performance of Fe2O3 for high-voltage asymmetric supercapacitors, here, a hybrid core-branch nanoarchitecture is proposed by integrating Fe2O3 nanoneedles on ultrafine Ni nanotube arrays (NiNTAs@Fe2O3 nanoneedles). The fabrication process employs a bottom-up strategy via a modified template-assisted method starting from ultrafine ZnO nanorod arrays, ensuring the formation of ultrafine Ni nanotube arrays with ultrathin tube walls. The novel developed NiNTAs@Fe2O3 nanoneedle electrode is demonstrated to be a highly capacitive anode (418.7 F g−1 at 10 mV s−1), matching well with the similarly built NiNTAs@MnO2 nanosheet cathode. Contributed by the efficient electron collection paths and short ion diffusion paths in the uniquely designed anode and cathode, the asymmetric supercapacitors exhibit an excellent maximum energy density of 34.1 Wh kg−1 at the power density of 3197.7 W kg−1 in aqueous electrolyte and 32.2 Wh kg−1 at the power density of 3199.5 W kg−1 in quasi-solid-state gel electrolyte.

Fabrication of N-doped Graphene–Carbon Nanotube Hybrids from Prussian Blue for Lithium–Sulfur Batteries

Abstract: Hybrid nanostructures containing 1D carbon nanotubes and 2D graphene sheets have many promising applications due to their unique physical and chemical properties. In this study, the authors find Prussian blue (dehydrated sodium ferrocyanide) can be converted to N-doped graphene–carbon nanotube hybrid materials through a simple one-step pyrolysis process. Through field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectra, atomic force microscopy, and isothermal analyses, the authors identify that 2D graphene and 1D carbon nanotubes are bonded seamlessly during the growth stage. When used as the sulfur scaffold for lithium–sulfur batteries, it demonstrates outstanding electrochemical performance, including a high reversible capacity (1221 mA h g−1 at 0.2 C rate), excellent rate capability (458 and 220 mA h g−1 at 5 and 10 C rates, respectively), and excellent cycling stability (321 and 164 mA h g−1 at 5 and 10 C (1 C = 1673 mA g−1) after 1000 cycles). The enhancement of electrochemical performance can be attributed to the 3D architecture of the hybrid material, in which, additionally, the nitrogen doping generates defects and active sites for improved interfacial adsorption. Furthermore, the nitrogen doping enables the effective trapping of lithium polysulfides on electroactive sites within the cathode, leading to a much-improved cycling performance. Therefore, the hybrid material functions as a redox shuttle to catenate and bind polysulfides, and convert them to insoluble lithium sulfide during reduction. The strategy reported in this paper could open a new avenue for low cost synthesis of N-doped graphene–carbon nanotube hybrid materials for high performance lithium–sulfur batteries.

Self‐Assembled Fe–N‐Doped Carbon Nanotube Aerogels with Single‐Atom Catalyst Feature as High‐Efficiency Oxygen Reduction Electrocatalysts

Abstract: Self-assembled M-N-doped carbon nanotube aerogels with single-atom catalyst feature are for the first time reported through one-step hydrothermal route and subsequent facile annealing treatment. By taking advantage of the porous nanostructures, 1D nanotubes as well as single-atom catalyst feature, the resultant Fe-N-doped carbon nanotube aerogels exhibit excellent oxygen reduction reaction electrocatalytic performance even better than commercial Pt/C in alkaline solution.

Observation of extreme phase transition temperatures of water confined inside isolated carbon nanotubes

Abstract: Fluid phase transitions inside single, isolated carbon nanotubes are predicted to deviate substantially from classical thermodynamics. This behaviour enables the study of ice nanotubes and the exploration of their potential applications. Here we report measurements of the phase boundaries of water confined within six isolated carbon nanotubes of different diameters (1.05, 1.06, 1.15, 1.24, 1.44 and 1.52 nm) using Raman spectroscopy. The results reveal an exquisite sensitivity to diameter and substantially larger temperature elevations of the freezing transition (by as much as 100 °C) than have been theoretically predicted. Dynamic water filling and reversible freezing transitions were marked by 2–5 cm−1 shifts in the radial breathing mode frequency, revealing reversible melting bracketed to 105–151 °C and 87–117 °C for 1.05 and 1.06 nm single-walled carbon nanotubes, respectively. Near-ambient phase changes were observed for 1.44 and 1.52 nm nanotubes, bracketed between 15–49 °C and 3–30 °C, respectively, whereas the depression of the freezing point was observed for the 1.15 nm nanotube between −35 and 10 °C. We also find that the interior aqueous phase reversibly decreases the axial thermal conductivity of the nanotube by as much as 500%, allowing digital control of the heat flux. A vibrational spectroscopy technique is used to study vapour, liquid and solid water within isolated carbon nanotubes and reveals phase transitions that show an extreme sensitivity to nanotube diameter, with melting temperatures higher than 100 °C for 1.05 and 1.06 nm diameter nanotubes and below 0 °C for 1.24 and 1.44 nm diameter nanotubes.

Plasmon-Enhanced Photoelectrochemical Water Splitting on Gold Nanoparticle Decorated ZnO/CdS Nanotube Arrays

Abstract: The design and decoration of plasmonic metal hybrid photoanodes provide an effective strategy for highly efficient photoelectrochemical (PEC) water splitting. In this work, an Au nanoparticle (NP) decorated highly ordered ZnO/CdS nanotube arrays (ZnO/CdS/Au NTAs) photoanode has been rationally designed and successfully synthesized. By virtue of the favorable band alignment and specific nanotube structure of ZnO/CdS as well as the surface plasmonic effect of Au NPs, the ZnO/CdS/Au NTAs photoanode shows significantly enhanced PEC performance as compared to the ZnO/CdS/Au and ZnO/CdS nanorod arrays (NRAs). Impressively, the optimized ZnO/CdS/Au NTAs photoanode exhibits the highest photocurrent density of 21.53 mA/cm2 at 1.2 V vs Ag/AgCl and 3.45% photoconversion efficiency (PCE) among the parallel photoanodes under visible light illumination (λ > 420 nm).

Photocatalysis with TiO2 Nanotubes: “Colorful” Reactivity and Designing Site-Specific Photocatalytic Centers into TiO2 Nanotubes

Abstract: Photocatalytic reactions on TiO2 have recently gained an enormous resurgence because of various new strategies and findings that promise to drastically increase efficiency and specificity of such reactions by modifications of the titania scaffold and chemistry. In view of geometry, in particular, anodic TiO2 nanotubes have attracted wide interest, as they allow a high degree of control over the separation of photogenerated charge carriers not only in photocatalytic reactions but also in photoelectrochemical reactions. A key advantage of ordered nanotube arrays is that nanotube modifications can be embedded site specifically into the tube wall; that is, cocatalysts, doping species, or junctions can be placed at highly defined desired locations (or with a desired regular geometry or pattern) along the tube wall. This allows an unprecedented level of engineering of energetics of reaction sites for catalytic and photocatalytic reactions, which target not only higher efficiencies but also the selectivity of re...

Metal-organic framework derived hollow CoS2 nanotube arrays: an efficient bifunctional electrocatalyst for overall water splitting.

Abstract: Self-supported hollow nanoarrays with hierarchical pores and rich reaction sites are promising for advanced electrocatalysis. Herein, we report a rational design of novel CoS2 nanotube arrays assembled on a flexible support which can be directly utilized as an efficient bifunctional electrocatalyst for overall water splitting. Uniform wire-like metal–organic framework (MOF) nanoarrays were first fabricated and a sulfidation process by thermal treatment was carried out to transform the MOF arrays into CoS2 nanotube arrays. The unique hollow CoS2 tubular arrays are shown to provide high surface area for an efficient electrochemical reaction, and the well-defined electrical/mechanical connection to the substrate enhances both mass and electron transfer. The CoS2 nanotube arrays exhibited a high electrochemical activity in catalyzing both oxygen and hydrogen evolution reactions, in terms of low onset potential, high current density and excellent stability. Using the CoS2 nanotube arrays as catalysts, a water-splitting current density of 10 mA cm−2 in alkaline solution is achieved with a cell voltage of 1.67 V, and the stable current can be maintained for 20 h even when the electrode is in a bent state.

Sorting Carbon Nanotubes

Abstract: Sorting of single-wall carbon nanotubes by their electronic and atomic structures in liquid phases is reviewed in this chapter. We first introduce the sorting problem, and then provide an overview of several sorting methodologies, following roughly the chronological order of their development over the past 15 years or so. Major methods discussed include ion-exchange chromatography, density-gradient ultracentrifugation, selective extraction in organic solvents, gel chromatography, and aqueous two-phase extraction. A main focus of the review is on the common mechanisms underlining all sorting processes. We propose that differences in solvation among different nanotube species are the ultimate driving force of sorting, and we corroborate this proposal by presenting analysis on how the differences are realized in electronic-structure-based sorting and atomic-structure-based sorting. In the end, we offer some suggestions on future directions that may grow out of carbon nanotube sorting. In particular, the prospect of expanding the function of DNA/carbon nanotube hybrid to control inter-particle interactions both inside and outside the nanotube is discussed.

Design of Amorphous Manganese Oxide@Multiwalled Carbon Nanotube Fiber for Robust Solid-State Supercapacitor.

Abstract: Solid-state fiber-based supercapacitors have been considered promising energy storage devices for wearable electronics due to their lightweight and amenability to be woven into textiles. Efforts have been made to fabricate a high performance fiber electrode by depositing pseudocapacitive materials on the outer surface of carbonaceous fiber, for example, crystalline manganese oxide/multiwalled carbon nanotubes (MnO2/MWCNTs). However, a key challenge remaining is to achieve high specific capacitance and energy density without compromising the high rate capability and cycling stability. In addition, amorphous MnO2 is actually preferred due to its disordered structure and has been proven to exhibit superior electrochemical performance over the crystalline one. Herein, by incorporating amorphous MnO2 onto a well-aligned MWCNT sheet followed by twisting, we design an amorphous MnO2@MWCNT fiber, in which amorphous MnO2 nanoparticles are distributed in MWCNT fiber uniformly. The proposed structure gives the amorp...

Electrochemical sensor based on multiwalled carbon nanotube and gold nanoparticle modified electrode for the sensitive detection of bisphenol A

Abstract: A novel electrochemical sensor for bisphenol A comprising a multiwalled carbon nanotube (MWCNT) and gold nanoparticle (AuNP) composite modified glassy carbon electrode has been developed. Differential pulse voltammetric and electrochemical impedance characterisation were carried out. Modified electrode architectures with different MWCNT loadings and different numbers of deposited AuNP layers were tested, as well as the influence of pH. Under the best experimental conditions, the sensor exhibited a linear response to BPA from 0.01 μM to 0.7 μM, with a limit of detection of 4 nM, one of the lowest achieved up until now. The reproducibility, repeatability and stability of the sensor were examined and are superior to those reported in the literature using similar architectures for BPA sensors. Perspectives for an impedimetric sensor at micromolar concentrations were also assessed. Finally, the selectivity with respect to common interferents was demonstrated and practical application of the developed modified electrode for the determination of BPA in waters was successfully carried out.

Covalently modified halloysite clay nanotubes: synthesis, properties, biological and medical applications

Abstract: Halloysite (HNT) is a promising natural nanosized tubular clay mineral that has many important uses in different industrial fields. It is naturally occurring, biocompatible, and available in thousands of tons at low cost. As a consequence of a hollow cavity, HNT is mainly used as nanocontainer for the controlled release of several chemicals. Chemical modification of both surfaces (inner lumen and outer surface) is a strategy to tune the nanotube's properties. Specifically, chemical modification of HNT surfaces generates a nanoarchitecture with targeted affinity through outer surface functionalization and drug transport ability from functionalization of the nanotube lumen. The primary focus of this review is the research of modified halloysite nanotubes and their applications in biological and medical fields.

Chirality-Controlled Synthesis and Applications of Single-Wall Carbon Nanotubes.

Abstract: Preparation of chirality-defined single-wall carbon nanotubes (SWCNTs) is the top challenge in the nanotube field. In recent years, great progress has been made toward preparing single-chirality SWCNTs through both direct controlled synthesis and postsynthesis separation approaches. Accordingly, the uses of single-chirality-dominated SWCNTs for various applications have emerged as a new front in nanotube research. In this Review, we review recent progress made in the chirality-controlled synthesis of SWCNTs, including metal-catalyst-free SWCNT cloning by vapor-phase epitaxy elongation of purified single-chirality nanotube seeds, chirality-specific growth of SWCNTs on bimetallic solid alloy catalysts, chirality-controlled synthesis of SWCNTs using bottom-up synthetic strategy from carbonaceous molecular end-cap precursors, etc. Recent major progresses in postsynthesis separation of single-chirality SWCNT species, as well as methods for chirality characterization of SWCNTs, are also highlighted. Moreover, w...

Hierarchical Multicomponent Electrode with Interlaced Ni(OH)2 Nanoflakes Wrapped Zinc Cobalt Sulfide Nanotube Arrays for Sustainable High‐Performance Supercapacitors

Abstract: High energy density, fast recharging ability, and sustained cycle life are the primary requisite of supercapacitors (SCs); these necessities can be fulfilled by engineering a smart current collector with hierarchical combination of different active materials. This study reports a multicomponent design of hierarchical zinc cobalt sulfide (ZCS) hollow nanotube arrays wrapped with interlaced ultrathin Ni(OH)2 nanoflakes for high-performance electrodes. The ZCS exhibits a unique pentagonal cross-section and a rough surface that facilitates the deposition of Ni(OH)2 nanoflakes with a thickness of 7.5 nm. The ZCS/Ni(OH)2 hierarchical electrode exhibits a high specific capacitance of 2156 F g−1 and excellent cyclic stability with 94% retention over 3000 cycles. This is attributed to enhanced redox reactions, the direct growth of arrays on 3D porous foam acting as a “superhighway” for electron transport, and the increased availability of electrochemical active sites provided by the ultrathin Ni(OH)2 flakes that also sustain the stability of the electrode by sacrificing themselves during long charge/discharge cycles. Symmetric SCs are assembled to achieve high energy density of 74.93 W h kg−1 and exhibit superior cyclic stability of 78% retention with 81% coulombic efficiency over 10 000 cycles.

Microstructure Design of Lightweight, Flexible, and High Electromagnetic Shielding Porous Multiwalled Carbon Nanotube/Polymer Composites.

Abstract: Multiwalled carbon nanotube/polymer composites with aligned and isotropic micropores are constructed by a facile ice-templated freeze-drying method in a wide density range, with controllable types and contents of the nanoscale building blocks, in order to tune the shielding performance together with the considerable mechanical and electrical properties. Under the mutual promotion of the frame and porous structure, the lightweight high-performance shielding is achieved: a 2.3 mm thick sample can reach 46.7 and 21.7 dB in the microwave X-band while the density is merely 32.3 and 9.0 mg cm−3, respectively. The lowest density corresponds to a value of shielding effectiveness divided by both the density and thickness up to 104 dB cm2 g−1, far beyond the conductive polymer composites with other fillers ever reported. The shielding mechanism of the flexible porous materials is further demonstrated by an in situ compression experiment.

Tuning Product Selectivity for Aqueous CO2 Reduction with a Mn(bipyridine)-pyrene Catalyst Immobilized on a Carbon Nanotube Electrode

Abstract: The development of high-performance electrocatalytic systems for the controlled reduction of CO2 to value-added chemicals is a key goal in emerging renewable energy technologies. The lack of selective and scalable catalysts in aqueous solution currently hampers the implementation of such a process. Here, the assembly of a [MnBr(2,2′-bipyridine)(CO)3] complex anchored to a carbon nanotube electrode via a pyrene unit is reported. Immobilization of the molecular catalyst allows electrocatalytic reduction of CO2 under fully aqueous conditions with a catalytic onset overpotential of η = 360 mV, and controlled potential electrolysis generated more than 1000 turnovers at η = 550 mV. The product selectivity can be tuned by alteration of the catalyst loading on the nanotube surface. CO was observed as the main product at high catalyst loadings, whereas formate was the dominant CO2 reduction product at low catalyst loadings. Using UV–vis and surface-sensitive IR spectroelectrochemical techniques, two different inte...

Radio frequency negative permittivity in random carbon nanotubes/alumina nanocomposites

Abstract: While metal is the most common conductive constituent element in the preparation of metamaterials, one-dimensional conductive carbon nanotubes (CNTs) provide alternative building blocks. Here alumina (Al2O3) nanocomposites with multi-walled carbon nanotubes (MWCNTs) uniformly dispersed in the alumina matrix were prepared by hot-pressing sintering. As the MWCNT content increased, the formed conductive MWCNT networks led to the occurrence of the percolation phenomenon and a change of the conductive mechanism. Two different types of negative permittivity (i.e., resonance-induced and plasma-like) were observed in the composites. The resonance-induced negative permittivity behavior in the composite with a low nanotube content was ascribed to the induced electric dipole generated from the isolated MWCNTs. The frequency dispersions of such negative permittivity can be fitted well by the Lorentz model, while the observed plasma-like negative permittivity behavior in the composites with MWCNT content exceeding the percolation threshold could be well explained by the low frequency plasmonic state generated from conductive nanotube networks using the Drude model. This work is favorable to revealing the generation mechanism of negative permittivity behavior and will greatly facilitate the practical applications of metamaterials.

Embedding CoS2 nanoparticles in N-doped carbon nanotube hollow frameworks for enhanced lithium storage properties

Abstract: The construction of metal sulfides-carbon nanocomposites with a hollow structure is highly attractive for various energy storage and conversion technologies. Herein, we report a facile two-step method for preparing a nanocomposite with CoS2 nanoparticles in N-doped carbon nanotube hollow frameworks (NCNTFs). Starting from zeolitic imidazolate framework-67 (ZIF-67) particles, in situ reduced metallic cobalt nanocrystals expedite the formation of the hierarchical hollow frameworks from staggered carbon nanotubes via a carbonization process. After a follow-up sulfidation reaction with sulfur powder, the embedded cobalt crystals are transformed into CoS2 nanoparticles. Benefitting from the robust hollow frameworks made of N-doped carbon nanotubes and highly active CoS2 ultrafine nanoparticles, this advanced nanocomposite shows greatly enhanced lithium storage properties when evaluated as an electrode for lithium-ion batteries. Impressively, the resultant CoS2/NCNTF material delivers a high specific capacity of ∼937 mAh·g–1 at a current density of 1.0 A·g–1 with a cycle life longer than 160 cycles.

Surviving High-Temperature Calcination: ZrO2-Induced Hematite Nanotubes for Photoelectrochemical Water Oxidation

Abstract: Nanotubular Fe2O3 is a promising photoanode material, and producing morphologies that withstand high-temperature calcination (HTC) is urgently needed to enhance the photoelectrochemical (PEC) performance. This work describes the design and fabrication of Fe2O3 nanotube arrays that survive HTC for the first time. By introducing a ZrO2 shell on hydrothermal FeOOH nanorods by atomic layer deposition, subsequent high-temperature solid-state reaction converts FeOOH-ZrO2 nanorods to ZrO2-induced Fe2O3 nanotubes (Zr-Fe2O3 NTs). The structural evolution of the hematite nanotubes is systematically explored. As a result of the nanostructuring and shortened charge collection distance, the nanotube photoanode shows a greatly improved PEC water oxidation activity, exhibiting a photocurrent density of 1.5 mA cm−2 at 1.23 V (vs. reversible hydrogen electrode, RHE), which is the highest among hematite nanotube photoanodes without co-catalysts. Furthermore, a Co-Pi decorated Zr-Fe2O3 NT photoanode reveals an enhanced onset potential of 0.65 V (vs. RHE) and a photocurrent of 1.87 mA cm−2 (at 1.23 V vs. RHE).

Anion selective pTSA doped polyaniline@graphene oxide-multiwalled carbon nanotube composite for Cr(VI) and Congo red adsorption.

Abstract: Multiwalled carbon nanotube (CNT)-graphene oxide (GO) composite was combined with polyaniline (Pani) using an oxidative polymerisation technique. The resulting Pani@GO-CNT was later doped with para toluene sulphonic acid (pTSA) to generate additional functionality. The functional groups exposed on the GO, Pani and pTSA were expected to impart a high degree of functionality to the pTSA-Pani@GO-CNT composite system. The composite was characterised by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The characterisation results revealed the characteristics of Pani, GO, CNT, and pTSA, and suggested the successful formation of the pTSA-Pani@GO-CNT composite system. The composite was utilised successfully for the adsorptive removal of Cr(IV) and Congo red (CR) dye and the adsorption of both pollutants was found to be strongly dependent on the solution pH, adsorbate concentration, contact time, and reaction temperature. The maximum adsorption of Cr(IV) and CR was observed in an acidic medium at 30 °C. The kinetics for Cr(IV) and CR adsorption was studied using pseudo-first order, pseudo-second order, and intraparticle diffusion models. The adsorption equilibrium data were also fitted to the Langmuir and Freundlich isotherm models. The thermodynamic results showed that the adsorption process was exothermic in nature. The present study provides a new methodology for the preparation of a highly functionalised Pani-based nanocomposite system and its potential applications to the adsorptive removal of a multicomponent pollutant system from an aqueous solution.

A potassium-rich iron hexacyanoferrate/dipotassium terephthalate@carbon nanotube composite used for K-ion full-cells with an optimized electrolyte

Abstract: K-ion batteries, as an emerging battery system, have attracted tremendous attention in the research community. Herein, we report a K-ion full-cell based on a nano-sized K1.92Fe[Fe(CN)6]0.94·0.5H2O cathode, dipotassium terephthalate (K2TP)@carbon nanotube (CNT) anode and an optimized electrolyte. K1.92Fe[Fe(CN)6]0.94·0.5H2O delivers a high capacity of 133 mA h g−1 with 92.8% capacity retention after 200 cycles and high coulombic efficiency of 98.5%. The side reactions of K metal with the electrolyte are suppressed in KClO4/propylene carbonate (PC). The K2TP nanosheets grown in situ on the CNT show a high reversible capacity of about 250 mA h g−1 and an ultra-high rate capability. The full-cells based on them are well cycled in a DME-based electrolyte and show a great promise for large-scale energy storage.

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

Abstract: 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. The one-dimensional Co9S8 nanotubes (NTs) serve as an ideal backbone to improve the electrical conductivity of Ni(OH)2 nanosheets, whereas the ultrathin and redox active Ni(OH)2 nanosheets electrodeposited on the Co9S8 NTs greatly enhance the surface area and provide more electroactive sites for faradaic reaction. The optimized Co9S8@Ni(OH)2 electrode shows high specific capacitances of 149.44 mA h g−1 at the current density of 1 A g−1 and 75 mA h g−1 even at 10 A g−1. An asymmetric supercapacitor was successfully assembled with this unique hybrid nanostructure as the anode and an active carbon film as the cathode. The as-fabricated device shows high energy density (31.35 W h kg−1 at 252.8 W kg−1), high power density (2500 W kg−1 at 12.5 W h kg−1), as well as a long-term cycle stability (97.3% retention of its initial capacitance after 5000 cycles). The as-prepared hierarchical nanostructure shows great potential as a promising electrode material for energy storage applications.

Doping effect on self-assembled films of polyaniline and carbon nanotube applied as ammonia gas sensor

Abstract: Here, composites based on carbon nanotubes and polyaniline films were tested as ammonia gas sensors with three different doping approaches (sulfuric acid, camphorsulfonic acid and m-cresol). The polyaniline high sensitivity to ammonia combined with the stability of the carbon nanotube increased the sensors reproducibility when compared to a regular polyaniline. The sensor in which the doping was performed by camphorsulfonic acid, presented the best sensor response for ammonia gas (418%) when compared to the others. This result is addressed to the better polymer configuration achieved by this procedure. The device's operation in low concentrations of ammonia indicates a strong adsorption process whit a limit of detection of 4 ppm.

Strongly coupled MoS2 nanoflake–carbon nanotube nanocomposite as an excellent electrocatalyst for hydrogen evolution reaction

Abstract: As a promising non-precious metal electrocatalyst for the hydrogen evolution reaction (HER), MoS2 suffers from impeded electrical conductivity and scarce active sites. This tricky situation can be ameliorated but not eliminated by the simple involvement of nanocarbons. Herein, a leaves-and-branch structure of strongly coupled and porous MoS2–carbon nanotube (CNT) nanocomposite was synthesized, where few-layer MoS2 nanoflakes are anchored radially and intimately on the surface of CNT. Mo–O–C has been unveiled to be the bridge between these two phases and a sandwich-like structure was proposed for the interface within the strongly coupled MoS2–CNT. This genuine nanocomposite exhibits remarkably improved electrocatalytic activity towards HER, reaching −850 mA cmgeo−2 with the expense of only 290 mV of overpotential and maintaining a low Tafel slope of 47 mV per decade even under a current density of 100 mA cmgeo−2. After detailed analysis, this surging activity has been ascribed not so much to the simple addition of the properties of MoS2 and CNT, but to a strong interfacial attachment between them which not only stabilizes tiny and edge-terminated MoS2 nanoflakes, but also constructs a three dimensional hierarchical structure to boost electron and mass transfer during the HER operation.