Carbon Nanotube Sponge Research Articles

Carbon Nanotube-Coupled Seaweed-like Cobalt Sulfide as a Dual-Functional Catalyst for Overall Water Splitting.

Preparation of high-efficiency dual-functional catalysts remains the bottleneck for electrochemical water splitting. To prepare a non-precious metal catalyst with high activity and stability, here, we present a seaweed-like structure consisting of transition-metal sulfide nanoplates self-assembled on carbon nanotube sponge networks (SW-CoS@CNT). By adjusting the key parameters during synthesis (e.g., the loading amount and ratio of Co and S precursors), the microstructure can be tailored in a wide range, and sulfur defects can be introduced into the nanoplates by thermal annealing. The resulting SW-CoS@CNT serves as a freestanding dual-functional catalytic electrode, showing low overpotentials of 105 and 218 mV for the hydrogen evolution reaction and the oxygen evolution reaction, respectively, which are superior to most reported transition-metal-sulfide-based catalysts in alkaline solution. Rational design of this hierarchical biomimetic structure may be useful in developing high-performance electrochemical catalysts in renewable energy and environmental fields.

Asymmetric electromagnetic shielding performance based on spatially controlled deposition of nickel nanoparticles on carbon nanotube sponge

Nowadays, the secondary reflection of electromagnetic waves (EMWs) emitted from various metal-based electromagnetic interference (EMI) shielding materials has produced serious health problems on human being. Therefore, efficient shielding materials with high EMI shielding performance but low reflection are highly expected. Here, we report a flexible Ni@CNTS/CNTS/PDMS composite with a designed asymmetric structure exhibits a unidirectional EMI shielding performance with controlled magnetic permeability, conductivity and enhanced mechanical property. The maximum EMI shielding effectiveness (SE) measured in the X band (8–12 GHz) is greater than 70 dB with the low average reflection shielding effectiveness (SER) of only 3.1 dB and the minimum reflection loss of about 0.71 at 12 GHz. The total EMI SE as well as the ratio of the adsorption to reflection is dominated by the amount of Ni particles and can be tuned by the Ni-deposition time. More interestingly, the asymmetric electro-magnetic structure leads to totally different EMI shielding performance with respect to wave incident direction: The reflection of EMWs at the nickel side is 17% lower than that at the bare CNTS side, while the total EMI SE value remains constant around 70 dB. Our findings provide a feasible and convenient strategy to reduce the reflection of highly conductive materials and precisely control the reflection to absorption ratio of EMI shielding materials.

Synthesis of hydrophilic carbon nanotube sponge via post-growth thermal treatment

Clean water is vital for healthy ecosystems, for human life and, in a broader sense, it is directly linked to our socio-economic development. Nevertheless, climate change, pollution and increasing world population will likely make clean water scarcer in the near future. Consequently, it becomes imperative to develop novel materials and more efficient ways of treating waste and contaminated water. Carbon nanotube (CNT) sponges, for example, are excellent in removing oleophilic contaminants; however, due to their super-hydrophobic nature, they are not as efficient when it comes to absorbing water-soluble substances. Here, by means of a scalable method consisting of simply treating CNT sponges at mild temperatures in air, we attach oxygen-containing functional groups to the CNT surface. The functionalized sponge becomes hydrophilic while preserving its micro- and macro-structure and can therefore be used to successfully remove toxic contaminants, such as pesticides, that are dissolved in water. This discovery expands the current range of applications of CNT sponges to those fields in which a hydrophilic character of the sponge is more suitable.

Visualized redox reaction guides polysulfide synthesis with electrochemical approach for long-cycle lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are promising next-generation energy storage systems. However, low active material utilization and sluggish reaction kinetics restrict their practical applications. Here, the redox reaction of these batteries was visualized, and their polysulfide component was established with their ultraviolet-visible absorption spectra through in-situ discharge observations. Liquid polysulfides with controllable component and concentration can be obtained by discharging solid sulfur into a determined potential. Fast and timely electrochemical conversion kinetics will occur due to the excellent wettability between polysulfides and carbon nanotube sponges (CNSs). In addition, the robust chemical interaction between liquid polysulfides and oxygen-containing groups inhibit the shuttle effect to a certain extent. Accordingly, the polysulfides-CNSs cathode demonstrates high sulfur utilization that exceeds 60% after 200 cycles. The obtained Li-S battery exhibits remarkably long cycling stability for 1500 cycles at 1 C with nearly 100% coulombic efficiency. This work provides valuable concepts for fabricating cathodes for Li-S batteries and for achieving their high-level services.

Exceptionally amino-quantitated 3D MOF@CNT-sponge hybrid for efficient and selective recovery of Au(III) and Pd(II)

• High-performance hybrid 30-MCNT was prepared for Au and Pd recovery. • 30-MCNT shows a superior selectivity to Au and Pd among other ten metals. • CNT sponge provides easier handpicked recycle framework to enhance recyclability. • Exceptional amino groups play the most critical roles for Au and Pd adsorption. • DFT simulation calculation elucidates interaction mechanisms during adsorption. Designing materials for selective recovery of precious metals is a critical challenge in response to recent outbreaks of electronic wastes owing to economic and environmental concerns. We introduced high-performance hybrid materials (MCNTs) comprising of six-amino groups based on hexaaminobenzene metal-organic framework (HAB-MOF) and carbon nano-tube (CNT) sponge for selective recovery of Au(III) and Pd(II). Among all MOFs ever reported in the literature, the particular synthesized 30-MCNT (30 mg HAB-MOF on CNT sponge) exhibited the highest adsorption capacity ( q e ) of 1832 mg/g (45 °C, pH 3.0) for Au(III) and 1651 mg/g (45 °C, pH 1.0) for Pd(II), which can be regarded as a benchmark in the MOF family. The highly selective nature of 30-MCNT was examined in the presence of ten different metal ions and the results showed that the Au(III)/Pd(II) adsorption efficiency was decreased by only 5–10%. Moreover, the Au(III) and Pd(II) recovery was maintained ∼ 100% from the initial solution with metal concentration of 200 mg/L. The superior performance was mainly attributed to the role of abundant amino groups in the hybrid framework, developing several types of interactions with Au(III) and Pd(II) ions such as hydrogen bonding, electrostatic interactions, acid-base affinity and π-π inner sphere complexation. Furthermore, the remarkably high surface area and robust chemical and mechanical stability of CNT-sponge provided an exceptional support for impregnation of HAB-MOF to avail greater active sites and easier handpicked recycle. Density functional theory (DFT) simulation and X-ray photoelectron spectroscopy (XPS) studies were employed to explore the interaction mechanisms during the adsorption processes. Owing to facile and environment-friendly synthesis, excellent recovery and recycling, the material can be possibly considered for industrial application in precious metal recovery.

Metal-Organic Framework-Derived Core-Shell Nanospheres Anchored on Fe-Filled Carbon Nanotube Sponge for Strong Wideband Microwave Absorption.

Metal-organic frameworks (MOFs) are booming as a promising precursor for constructing lightweight, high-efficiency microwave absorbing (MA) material. However, it is still a challenge to rationally design three-dimensional (3D), porous MOF-derived MA materials with a stable structure and strong and wideband MA performance. Herein, a 3D hybrid nanostructure (CNT/FeCoNi@C) comprising MOF-derived magnetic nanospheres and Fe-filled carbon nanotube (CNT) sponge has been controllably fabricated to enhance the absorption ability and broaden the effective absorption bandwidth (EAB). The magnetic nanospheres are uniformly anchored on the CNT skeleton, forming hybrid network structures, which enhance interface polarization, electron transportation, and impedance matching. The minimum reflection loss (RL) and EAB of the as-prepared CNT/FeCoNi@C sponges reach -51.7 dB and 6.0 GHz, respectively, outperforming most reported MOF-based wave absorbers. This work provides not only a novel design of MOF-derived 3D nanostructures but also an effective guide for the optimization of electromagnetic properties and absorbing performance in MA material.

High-Performance Flexible Solid-State Supercapacitors Based on MnO2-Decorated Carbon Nanotube Sponge with Ultra-high Capacitance, Long Cycling Life, and Enhanced Mechanical Strength

High-Performance Flexible Solid-State Supercapacitors Based on MnO₂-Decorated Carbon Nanotube Sponge with Ultra-high Capacitance, Long Cycling Life, and Enhanced Mechanical Strength

Asymmetric Electromagnetic Shielding Performance Based on Spatially Controlled Deposition of Nickel Nanoparticles on Carbon Nanotube Sponge

Asymmetric Electromagnetic Shielding Performance Based on Spatially Controlled Deposition of Nickel Nanoparticles on Carbon Nanotube Sponge

Heterostructure NiS2/NiCo2S4 nanosheets array on carbon nanotubes sponge electrode with high specific capacitance for supercapacitors

Nickel cobalt sulfur is attracting more attention due to its great electrical conductivity and high specific capacitance for faraday pseudo-capacitors. Here, by evaporation-induced drying, heterostructure NiS 2 /NiCo 2 S 4 nanosheets on self-supporting substrate of nitrogen-doped single-walled carbon nanotubes sponge (NSCS) are obtained with the sponge volume significantly being reduced. With the electrode film thickness being 80 μm, the as-prepared heterostructure NiS 2 /NiCo 2 S 4 /NSCS electrode shows outstanding areal/gravimetric/volumetric capacitance of 10.5 F cm −2 /2905 F g −1 /1307.2 F cm −3 at 1 A g −1 . With the increase of current density from 1 to 60 A g −1 , the current retention rate maintains at 61%. When the active material loading is increased to 14 mg cm −2 , the gravimetric capacitance can still maintain at 1725 F g −1 , indicating the high ratio performance. After 10,000 cycles, the capacity retention still remains 83% at current density of 10 A g −1 . In addition, an asymmetric supercapacitor (ASC) delivers have high gravimetric/volumetric energy density of 58.1 W h kg −1 /52.3 W h L −1 with excellent cycle stability after 20,000 cycles. Therefore, the electrode material with high loading and high rate performance can be realized by this method. • By evaporation-induced drying, the volume of NiS 2 /NiCo 2 S 4 /NSCS shrinks obviously. • The electrode has high areal and volumetric capacitance with high loading. • Heterostructure material of NiS 2 /NiCo 2 S 4 greatly improves the electrochemical performance. • The asymmetric supercapacitor delivers high gravimetric/volumetric energy density.

In-situ characterization on the fracture behavior of three dimensional polymer nanocomposites reinforced by CNT sponge

This paper reported the fracture behavior of polymer-based nanocomposites reinforced by carbon nanotubes (CNTs). In order to solve the problem associated with the dispersion and re-agglomeration of CNTs, three dimensional CNT sponge was prepared and incorporated into the epoxy through the monomer infusion process. The fracture toughness and critical energy release rate of the nanocomposites were enhanced by more than 100% and 250%, respectively. The toughening mechanism behind such observation was revealed by studying the in-situ crack initiation and propagation in the bulky nanocomposites with assistance of micro-mechanical testing device in a scanning electronic microscope chamber. The results showed that the intrinsic fracture behaviors, such as void generation, as well as the extrinsic toughening features arising from crack deflection and bifurcation, were responsible for the improved fracture properties of nanocomposites.

High-Sensitivity Flexible Pressure Sensor-Based 3D CNTs Sponge for Human-Computer Interaction.

Researchers are showing an increasing interest in high-performance flexible pressure sensors owing to their potential uses in wearable electronics, bionic skin, and human–machine interactions, etc. However, the vast majority of these flexible pressure sensors require extensive nano-architectural design, which both complicates their manufacturing and is time-consuming. Thus, a low-cost technology which can be applied on a large scale is highly desirable for the manufacture of flexible pressure-sensitive materials that have a high sensitivity over a wide range of pressures. This work is based on the use of a three-dimensional elastic porous carbon nanotubes (CNTs) sponge as the conductive layer to fabricate a novel flexible piezoresistive sensor. The synthesis of a CNTs sponge was achieved by chemical vapor deposition, the basic underlying principle governing the sensing behavior of the CNTs sponge-based pressure sensor and was illustrated by employing in situ scanning electron microscopy. The CNTs sponge-based sensor has a quick response time of ~105 ms, a high sensitivity extending across a broad pressure range (less than 10 kPa for 809 kPa−1) and possesses an outstanding permanence over 4000 cycles. Furthermore, a 16-pixel wireless sensor system was designed and a series of applications have been demonstrated. Its potential applications in the visualizing pressure distribution and an example of human–machine communication were also demonstrated.

N‐doped carbon nanotube sponges and their excellent lithium storage performances

AbstractPreparation, analysis and lithium storage performance of a series of nitrogen‐doped carbon nanotube sponges (CNX) is presented in this work. The synthesis was performed using an aerosol‐assisted chemical vapor deposition (AACVD) in a bi‐sprayer system by using various carbon and nitrogen precursors made of mixtures of benzylamine with toluene, urea, pyridine and 1,2‐dichlorbenzene, with ferrocene as catalyst. A series of physico‐chemical analysis techniques are used to characterize the composition and the morphology of the obtained materials, and a correlation of these with the lithium storage performances is attempted. The samples reveal an interconnected core‐shell CNX fiber morphology with a CNT‐core surrounded by an amorphous carbon shell. Appealing lithium storage performances are attained, while also considering aspects of safety, low potential, and long‐term cycling stability. The best performing sponges display a high specific capacity (223 mAh g−1) when cycled in a practically relevant voltage window (0.01–1V vs. Li), high first cycle (90%) and long‐term cycling (99.3%) coulombic efficiencies and excellent capacity retention after 1500 cycles. This study further analyses the interplay between the morphology and the physico‐chemistry of nitrogen‐doped carbon nanotube materials for Lithium storage and provides guidelines for future developments.

Long-life lithium-sulfur batteries with high areal capacity based on coaxial CNTs@TiN-TiO2 sponge

Rational design of heterostructures opens up new opportunities as an ideal catalyst system for lithium polysulfides conversion in lithium-sulfur battery. However, its traditional fabrication process is complex, which makes it difficult to reasonably control the content and distribution of each component. In this work, to rationally design the heterostructure, the atomic layer deposition is utilized to hybridize the TiO2-TiN heterostructure with the three-dimensional carbon nanotube sponge. Through optimizing the deposited thickness of TiO2 and TiN layers and adopting the annealing post-treatment, the derived coaxial sponge with uniform TiN-TiO2 heterostructure exhibits the best catalytic ability. The corresponding lithium-sulfur battery shows enhanced electrochemical performance with high specific capacity of 1289 mAh g−1 at 1 C and capacity retention of 85% after 500 cycles at 2 C. Furthermore, benefiting from the highly porous structure and interconnected conductive pathways from the sponge, its areal capacity reaches up to 21.5 mAh cm−2.

Metal-Organic Frameworks Reinforce the Carbon Nanotube Sponge-Derived Robust Three-Dimensional Sulfur Host for Lithium-Sulfur Batteries.

Sulfur is a prospective material for next-generation batteries with high theoretical capacity, but its drawbacks hinder its commercialization. To overcome the low conductivity of natural sulfur and the shuttle effect of lithium polysulfide, the study proposes a novel sulfur film coated with three-dimensional nitrogen and cobalt-codoped polyhedral carbon wrapped on a multiwalled carbon nanotube sponge (3D-S@NCoCPC sponge) composite as a high-performance cathode material for rechargeable lithium-sulfur batteries. The interconnected conductive carbon network with abundant pores provides more room for the homogeneous distribution of sulfur within the composite and creates a favorable pathway for electrolyte permeability and lithium-ion diffusion. Moreover, the strong interaction between cobalt and lithium polysulfides leads to efficient suppression of the shuttle effect. In addition, the homogeneous distribution of sulfur and cobalt within the composite enhances electronic transfer for the conversion reaction of sulfur. As expected, the cathode with a high sulfur content of 77.5 wt % in the composite achieved a high initial discharge capacity of 1192 mA h g-1 and high Coulombic efficiency of 99.98% after 100 cycles at 100 mA g-1 current density. Stable performance was achieved with 92.9% capacity retention after 200 cycles at 1000 mA/g current density.

High-energy-density Li–S battery with positive electrode of lithium polysulfides held by carbon nanotube sponge

Lithium-sulfur battery suffers from the low utilization of sulfur and the high electrolyte/sulfur (E/S) ratio that decrease the cell-based performance. Lithium polysulfides (Li2Sx)-dissolved electrolyte, so called catholyte, enables high utilization of sulfur, but the cell inherently has high E/S ratio due to the limited solubility of Li2Sx. Herein, a composite electrode of Li2Sx (x = 4, 6, 8) and sub-millimeter-long few-wall carbon nanotube (CNT) is proposed. The CNT forms self-supporting sponge-like paper and works as a three-dimensional current collector, in which the Li2Sx is deposited by solution casting and drying. The Li2S6-CNT electrode realizes high specific capacity (1249 mAh gsulfur−1) under a lean electrolyte condition of E/S = 4 μL mgsulfur−1, which is much better than the S8-CNT electrode (233 mAh gsulfur−1). After full charge and conversion of Li2Sx to S, the Li2Sx-CNT electrode maintains its high capacity of 1100 mAh gsulfur−1. The full cell with the Li2S6-CNT and the Li thin foil electrodes realizes 400–500 Wh kgcell−1 for E/S = 4.0 at the 2nd and 3rd discharge and 300 Wh kgcell−1 for E/S = 5.8 at the 97th discharge, based on the total mass of the interior of a cell (electrodes, separator, and electrolyte). Holding solvated Li2Sx by the CNT sponge is the key for the high energy density.

Potential Use of Nitrogen-Doped Carbon Nanotube Sponges as Payload Carriers Against Malignant Glioma.

Glioblastoma is the most aggressive brain tumor with a low median survival of 14 months. The only Food and Drug Administration (FDA)-approved treatment for topical delivery of the cancer drug carmustine is Gliadel. However, its use has been associated with several side-effects, mainly provoked by a mass effect. Nitrogen-doped carbon nanotube sponges (N-CNSs) are a new type of nanomaterial exhibiting high biocompatibility, and they are able to load large amounts of hydrophobic drugs, reducing the amount of carriers. This study evaluated the use of N-CNSs as potential carmustine carriers using malignant glioma cell lines. N-CNSs were characterized by nanoparticle tracking analysis and transmission electron microscopy. The biocompatibility of N-CNSs was determined in glioma cell lines and in primary astrocytes. Afterward, N-CNSs were loaded with carmustine (1:10 w/w), and the drug and liberation efficiency, as well as cytotoxicity induction, were determined. N-CNSs presented a homogeneous size distribution formed by round nanotubes, without induced cytotoxicity, at concentrations below 40 µg/mL. The N-CNSs loaded with carmustine exhibited a continuous kinetic release of carmustine with a maximum release after 72 h. The cytotoxic effect of N-CNSs loaded with carmustine was similar to that of carmustine alone. The results demonstrated that N-CNSs are a biocompatible nanostructure that could be used as carriers for the tumoral load of large amounts of chemotherapeutic agents.

Thermal conductivity and thermoelectric properties in 3D macroscopic pure carbon nanotube materials

Abstract Sintered carbon nanotube (CNT) blocks and porous CNT sponges were prepared, and their thermoelectric properties were measured. The maximum dimensionless thermoelectric figure-of-merit, ZT, at room temperature of the sintered single-walled carbon nanotube (SWCNT) block is 9.34 × 10−5, which is twice higher than that of the sintered multi-walled carbon nanotube (MWCNT) block in this work and also higher than that of other sintered MWCNT blocks reported previously. In addition, the porous MWCNT sponge showed an ultra-low thermal conductivity of 0.021 W/(m K) and significantly enhanced ZT value of 5.72 × 10−4 at room temperature and 1 atm. This ZT value is higher than that of other 3D macroscopic pure CNT materials reported. The pronounced enhancement of the ZT in the porous MWCNT sponge is attributed to the ultra-low density, ultra-high porosity, and interconnected structure of the material, which lead to a fairly low thermal conductivity and better Seebeck coefficient. The finding of this work provides an understanding for exploring potential enhancement mechanisms and improving the thermoelectric properties of CNT-based thermoelectric composites.

Highly Selective Adsorption and Desorption of Charged Molecules in Three-Dimensional Networks of Polydopamine-Modified Carbon Nanotube Sponges.

We investigated the selective adsorption and desorption behaviors of charged molecules (calcein, brilliant green, and methylene blue) dissolved in water using polydopamine-modified carbon nanotube (CNT) sponges. Porous CNT sponges (CNTSs) as a scaffold for the selective adsorption and desorption of aqueous molecules were fabricated by using a chemical vapor deposition technique. To improve the hydrophilicity of porous CNTS and to control the adsorption and desorption of aqueous molecules, CNT sidewalls were decorated with a hydrophilic polydopamine layer through noncovalent interactions between CNT sidewalls and polydopamine. After this noncovalent chemical modification, the water contact angle of CNTS was close to 0, and the aqueous solution can rapidly infiltrate the three-dimensional (3D) networks of polydopamine-modified CNTS (Pdop-CNTS). The incorporation of pH-responsive polydopamine in CNTS showed an evident advantage of adsorbing positively charged molecules over a pH range of 10.5-4. In aqueous solutions with pH value of ≤3, Pdop-CNTS selectively adsorbed negatively charged molecules. Aqueous molecules carrying net charges were successfully separated from mixture solutions. Moreover, charged calcein and methylene blue molecules adsorbed on the 3D networks of Pdop-CNTS were selectively desorbed from Pdop-CNTS by tuning the pH value of the desorption solution.

An Ultra‐sensitive Electrochemiluminescent Detection of Carcinoembryonic Antigen Using a Hollowed‐out Electrode

AbstractUltrasensitive detection of cancer biomarkers has attracted considerable attention recently in academic research and clinic diagnostics. Here, we use a hollowed‐out carbon nanotube sponge (CNTSP) electrode to fabricate an immunosensor to realize the sensitive detection of carcinoembryonic antigen (CEA). Nitrogen‐doped carbon quantum dots (N‐CDs) are combined with antibody that can specially recognize CEA and used as the electrochemiluminescent (ECL) probes in this work. The hollowed‐out and permeable CNTSP facilitates chemical species exchange on the surface of electrode, offering an enhanced ECL signal. The resulting ECL immunosensor enables the determination of CEA concentration to be in a wide linear range from 0.005 to 50 pg mL−1 with a detection limit of 1.4 fg mL−1. Furthermore, with good stability, acceptable precision and reproducibility, the proposed ECL assay strategy offers a wide application potential in clinical analysis.

3D Hierarchical NiCo2S4 Nanoparticles/Carbon Nanotube Sponge Cathode for Highly Compressible Asymmetric Supercapacitors

By employing a carbon nanotube (CNT) sponge with a 3D porous network as a compressible substrate and NiCo2S4 nanoparticles as active materials, a NiCo2S4/CNT sponge electrode with high compression ...