Series Of Carbon Nanotubes Research Articles

Size-dependent Copper Nanoparticles Supported on Carbon Nanotubes with Balanced Cu+ and Cu0 Dual Sites for the Selective Hydrogenation of Ethylene Carbonate.

Cyclic carbonate hydrogenation offers an alternative for the efficient indirect CO2 utilization. In this study, a series of carbon nanotubes (CNTs) supported xCu/CNTs catalysts with different Cu loadings were fabricated using a convenient impregnation method, and exhibited excellent catalytic activity for the hydrogenation of ethylene carbonate to methanol and ethylene glycol. The structural and physicochemical properties revealed that acid treatment of CNTs resulted in plentiful oxygen-containing functional groups, providing sufficient anchoring sites for copper species. The calcination process conducted under an inert atmosphere resulted in the formation of ternary CuO, Cu2O, and Cu composites, enhancing the metal-support interaction and facilitating the formation of balanced Cu0 and Cu+ dual sites as well as high active surface area after reduction. Contributed to the synergetic effect of balanced Cu+ and Cu0 species proved by density functional theory calculation and the electron-rich CNTs surface, the 40Cu/CNTs catalyst achieved strengthened catalytic performance with methanol yield of 83%, ethylene glycol yield of 99% at ethylene carbonate conversion of >99%, and 150 h of long-term running stability. Consequently, CNTs supported Cu serve as efficient non-silica based catalyst for ester hydrogenation.

Carbon nanotubes decorated FeNi/nitrogen-doped carbon composites for lightweight and broadband electromagnetic wave absorption

Magnetic-dielectric component modulation and heterogeneous interface engineering were considered as an effective strategy for designing lightweight and broadband electromagnetic wave (EMW) absorbors. Herein, a series of carbon nanotubes (CNTs) decorated core-shell nitrogen-doped carbon (CNTs/FeNi/NC) composites were successfully fabricated via the carbonization of CNTs/NiFe2O4/PDA precursors obtained by hydrothermal and polymerization method. The EMW absorption (EMWA) properties of CNTs/FeNi/NC composites were explored by varying the CNTs content. When the CNTs content was 15%, the minimum reflection loss (RLmin) value was -51.13 dB at 9.52 GHz and the corresponding effective absorption bandwidth (EAB) value was 2.96 GHz (8.96–11.12 GHz) at 2.5 mm. Particularly, the maximum EAB value can reach up to 4.64 GHz (12.80–17.44 GHz) at 1.7 mm. The excellent EMW attenuation capability resulted from the enhanced conductive loss, polarization loss, magnetic loss, and improved impedance matching. This work offers a novel reference for designing lightweight and broadband EMWA materials.

Controllable Synthesis of MoC and Mo2C to Boost Hydrogen Generation from Ammonia Borane Hydrolysis

Ammonia borane has been proposed as a competitor to boost H2 evolution via the catalytic hydrolysis reaction at mild temperatures. A series of carbon nanotubes (CNTs)-supported Ni–MoxC catalysts with different MoxC crystalline phases are controllably synthesized using a facile two-step impregnation method followed by the thermal treatment. The catalyst structure and physicochemical properties are studied. The incorporation of MoxC is effective for enhancing the catalytic activity of Ni/CNTs, and the β-Mo2C is more beneficial to the ammonia borane hydrolysis than the α-MoC. 10Ni30Mo2C/CNTs exhibit superior catalytic activity with a turnover frequency (TOF) value of 71.0 min–1. Both experimental and theoretical results suggest that MoxC is responsible for H2O adsorption and activation while Ni is contributed to the ammonia borane molecule. Thus, this synergistic effect between MoxC and Ni enhances the catalytic hydrolysis of ammonia borane. This finding demonstrates the huge potential of MoxC for ammonia borane hydrolysis in hydrogen storage applications and provides a fangled sight for developing a unique class of low-cost catalytic system.

The preparation of rigid hybrid silicone resins by combining carbon nanomaterial loading nanoparticles

AbstractA series of carbon nanotubes and graphene loading nanoparticles (Mo, Ru, and Pt) were synthesized by the ethylene glycol reduction, in addition, the nanomaterials went through the silanization process by (3‐aminopropyl)triethoxysilane in order to obtain the perfect consistency and dispersibility. The characterization results were then exhibited by X‐ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy tests. Furthermore, the nanomaterials modified silicone resins were obtained by combining methyl phenyl silicone resins, nanocarbon material and HOOBt. The differential scanning calorimetry, sol–gel time and thermogravimetric analysis tests showed the preferable improvement of heat‐resistant quality. Then the silicone resin matrix composites were manufactured by molding process and went through a thermal decomposition process. The ILSS, bending strength and modulus results showed that the hybrid modified silicone resin composites had the leading trend (361.4 MPa, 190.3 MPa, 13.5 GPa, etc.) at all temperature stages. This experimental scheme of carbon nanomaterial loading nanoparticles and hybrid modified silicone resins would have a competitive advantage in exotic material field.

在水系锌电池中通过孔相双调控实现碳纳米管@硒化镍的快速动力学活化

Metal chalcogenide compounds can be used as high-performance cathodes for aqueous Zn batteries. However, the low accessible surfaces and violent volumetric expansion limit their properties and applications. To address these, phase-engineering strategies coupled with a hollow structure were applied to regulate the adsorption/desorption of OH− on the electrode surface and enhance the electrochemical performance. In this study, using a Se@C nanorod template, a series of carbon nanotube (CNT)-supported nickel selenides, including cubic NiSe2, NiSe2/Ni0.85Se composites, and hexagonal Ni0.85Se, were synthesized through an in situ selenylation process for the first time. Due to the large specific surface, high porosity, and hollow carbon skeleton, the optimized NiSe2/Ni0.85Se/CNT has a high specific capacity of 616 Cg−1, excellent rate capability, and stable cycling performance. In addition, its inside Faradic mechanism was investigated using a series of ex situ characterizations and density functional theory calculations. Thus, the fabricated Ni//Zn battery presents a high energy density of 311.4 W h kg−1 at 3485 W kg−1 and long cycling life. This study offers an ingenious strategy for designing nickel selenide electrodes and deeper perception for its Faradic mechanism in alkaline Zn battery.

Selective aqueous‐phase hydrogenation of furfural to cyclopentanol over Ni‐based catalyst under mild conditions

AbstractA series of carbon nanotube (CNT)‐supported Ni‐based catalysts were prepared through a simple impregnation method. The synthesized Ni‐based bimetallic catalysts exhibited much smaller particle size and better dispersion than monometallic Ni/CNT catalyst. Owing to the synergistic effect of Ni with Mo, the material was especially active to hydrogenation of biomass derivatives in aqueous medium. Promotional effect was observed in NiMo/CNT catalyst during hydrogenation of furfural to fine chemicals, including cyclopentanone/cyclopentanol, which is of profound practical values for processing biomass degradation and may be applied in the food and biomass refining industry.

Facile Preparation of CNT/Ag2S Nanocomposites with Improved Visible and NIR Light Photocatalytic Degradation Activity and Their Catalytic Mechanism.

In this work, a series of carbon nanotubes (CNT)/Ag2S hybrid nanocomposites were successfully prepared by a facile precipitation method. Transmission electron microscope (TEM) observation indicates that Ag2S nanoparticles with an average particle size of ~25 nm are uniformly anchored on the surface of CNT. The photocatalytic activities of the CNT/Ag2S nanocomposites were investigated toward the degradation of rhodamine B (RhB) under visible and near-infrared (NIR) light irradiation. It is shown that the nanocomposites exhibit obviously enhanced visible and NIR light photocatalytic activities compared with bare Ag2S nanoparticles. Moreover, the recycling photocatalytic experiment demonstrates that the CNT/Ag2S nanocomposites possess excellent photocatalytic stability. The photoelectrochemical and photoluminescence measurements reveal the efficient separation of photogenerated charges in the CNT/Ag2S nanocomposites. This is the dominant reason behind the improvement of the photocatalytic activity. Based on active species trapping experiments, the possible photocatalytic mechanism of CNT/Ag2S nanocomposites for dye degradation under visible and NIR light irradiation was proposed.

Photocatalytic degradation of phenol wastewater over Z-scheme g-C3N4/CNT/BiVO4 heterostructure photocatalyst under solar light irradiation

A series of carbon nanotubes (CNT) modified g-C3N4/BiVO4 photocatalysts were synthesized via wet-impregnation method and evaluated via degradation of phenol under solar light irradiation. The physicochemical properties of the as-developed photocatalyst were characterized using FTIR, XRD, FESEM, XPS, SAP and DR-UV Vis. The formation of g-C3N4/CNT/BiVO4 photocatalysts resulted in remarkable enhancement in the performance in which almost six times higher degradation rate in comparison to the pristine g-C3N4 and obeyed the pseudo-first-order kinetics and Temkin adsorption model. Congruously, the synergistic interaction between 2 wt% of CNT and 5 vol% of H2O2 as an oxidizing agent was capable of removing 80.6% of phenol within 120 min. The profound photodegradation performance monitored was attributed to the better crystallinity structure obtained as shown in XRD and XPS analysis. Furthermore, the intimate contact between the CNT, g-C3N4 and BiVO4 in the heterostructure sample as shown in FESEM micrograph images does help in allowing a smooth electron-hole pair separation and migration, resulting in more available •OH and •O2¯ radicals for photocatalytic degradation activities. The possible Z-scheme reaction mechanism has been proposed and active species trapping experiments have been carried out to find the role of active radical species responsible for the phenol degradation. Additionally, the g-C3N4/CNT/BiVO4 photocatalysts retained excellent stability even after several cycles. Congruently, a mathematical representation for understanding the interaction between CNT loading and H2O2 for photodegradation of phenol using response surface methodology (RSM) was successfully generated.

On the role of water in selective hydrogenation of cinnamaldehyde to cinnamyl alcohol on PtFe catalysts

A series of carbon nanotube (CNT)-supported bimetallic PtFe nanoparticles were synthesized and employed as catalysts for hydrogenation of cinnamaldehyde in pure water. A synergy between water and bimetallic PtFe catalysts has allowed the efficiently selective production of cinnamyl alcohol. With the aid of water, an initial reaction rate of >1200 h−1 and a high selectivity of >97%, as well as a good cycling stability, were achieved with a Pt3Fe/CNT catalyst under mild reaction conditions. Isotopic labeling studies and theoretic calculation results demonstrated that the water-involved hydrogen-exchange pathway occurred with a lower energy barrier, which coexisted with the pathway of direct H2 dissociation–hydrogenation. This work also suggested that water participated in the catalytic hydrogenation reaction by serving as a hydrogen-exchange bridge.

Carbon Nanotube-Supported Amorphous Co–B for Hydrogenation of M-chloronitrobenzene

A series of carbon nanotube (CNT)-supported amorphous Co–B alloy catalysts were prepared by selectively depositing Co–B particles inside and/or outside of CNTs. The effects of the nanotubular structure on the physiochemical properties of the amorphous Co–B alloys were studied. It was found that the internal loading enhanced the thermal stability of the amorphous Co–B alloys and inhibited the loss of Co compared with the external loading. The internal loading also increased the proportion of elemental Co in the Co–B alloys, while the loading method did not change the valence states of either Co or B. The internally loaded Co–B particles exhibited higher hydrogenation activity for m-chloronitrobenzene ( m-CNB) than the externally loaded analogue. The kinetics of m-CNB hydrogenation were also studied.

Catalytic conversion of cellulose into polyols using carbon-nanotube-supported monometallic Pd and bimetallic Pd–Fe catalysts

A series of carbon nanotube (CNT)-supported monometallic Pd and bimetallic Pd–Fe catalysts were synthesized and employed for catalytic hydrogenolysis of cellulose into polyols, including hexitol, ethylene glycol (EG), 1,2-propanediol (1,2-PG), and glycerol (Gly). The physicochemical properties of the catalysts were characterized by nitrogen physical adsorption measurements, X-ray diffraction analysis, transmission electron microscopy, and X-ray photoelectron spectroscopy. The total yield of hexitol, EG, 1,2-PG, and Gly in hydrolytic hydrogenation of cellulose was 37, 55, and 53% for Pd/CNTs, Pd–Fe/CNTs (Pd:Fe = 1:1), and Pd–Fe/CNTs (Pd:Fe = 1:2), respectively. Addition of Fe to Pd significantly modified the physicochemical properties of the nanoparticles and their catalytic performance, especially regarding hexitol selectivity. The promoting effect of Fe, especially for hexitol selectivity, compared with the monometallic catalyst is due to the fact that incorporation of Fe may stabilize Pd0 nanoparticles and lead to downshift of the d-band center of Pd metal nanoparticles by charge transfer from Fe to Pd. Recycling experimental results showed that leaching of Fe resulted in a significant decrease in the hexitol yield obtained using the Pd–Fe/CNTs after the first recycle, further demonstrating that Fe element plays a promoting role for hexitol formation.

Carbon Nanotube-Supported Copper-Cobalt Catalyst for the Production of Higher Carbon Number Alcohols through Carbon Monoxide Hydrogenation

A series of carbon nanotube (CNTs)-supported copper-cobalt catalysts were prepared and investigated in a slurry reactor for their ability to selectively convert syngas into higher carbon number alcohols. The 7.5Cu7.5Co/CNTs catalyst achieved superior selectivity towards the formation of ethanol (30.1%) and C2+ alcohols (57.7%), while the 10Co5Cu/CNTs catalyst exhibited the largest alcohol space-time yield (372.9 mg gcat -1 h-1). However, the pure Cu (15Cu/CNTs) catalyst displayed negligible activity. Cobalt reduction was enhanced in the presence of copper. In addition to the Cu0-Co0 center, Co0-Co2+ also presented dual active sites for higher alcohols synthesis, the Co2+ site could terminate carbon chain growth to produce alcohols. The ratio of Cu/Co considerably influences the metal particle properties-synergistically effecting the active species.

New findings on the influence of carbon surface curvature on energetics of benzene adsorption from gaseous phase

In this Letter, new results of calorimetric study on benzene adsorption from the gaseous phase are presented. According to some of recently published reports, the energy of solid–fluid, interactions increases with the rise in carbon nanotube curvature during adsorption. The recent considerations [Chem. Phys. Lett. 619 (2015) 219] on thermodynamics of adsorption from aqueous solutions on a series of carbon nanotubes have confirmed this observation. Although comparable ‘energy–tube diameter’ relations for benzene adsorption from the solution and from the gaseous phase are observed, remarkable differences between the mechanisms of the both processes caused by surface heterogeneity are noticeable.

Effect of the dimensions of carbon nanotube channels on copper–cobalt–cerium catalysts for higher alcohols synthesis

A series of carbon nanotube (CNT)-supported copper–cobalt–cerium catalysts were prepared and investigated for higher alcohols synthesis. The superior selectivity for the formation of ethanol and C2+ alcohols achieved using the CuCoCe/CNT(8) catalyst was 39.0% and 67.9%, respectively. The diameters of CNTs considerably influence the distribution of metal particles and the electronic interaction between the tube surface and the active species. The electronic effect between the encapsulated Co species and the inner surface is greatly improved in the narrowest CNT channel, which is expected to facilitate the reduction of cobaltous oxide and promote the alcohols yield remarkably (291.9mg/gcath).

Effect of confinement on the structure and energetics of Zundel cation present inside the hydrophobic carbon nanotubes: an ab initio study

Protonated water clusters confined to the carbon nanotube (CNT) channels of sub-nanometer diameter is beyond the realm of a continuum description. The steric compulsions offered by the narrow geometry can restrict the formation of hydrogen bond between the water molecules but enhance water and channel interactions. Herein, we have made an attempt to investigate the factors, which are strongly affecting the structure and energy barrier for proton transfer in Zundel cation under the confinement of CNT by employing dispersion-corrected density functional theory-based methods. Our results reveal that the diverse nature of water–water and water–wall interaction inside the nanotube for different size of CNT channels can have remarkable effects on the energetics of the proton transfer process, geometrical parameters, oscillatory shuttling motion of the proton and various energy components, viz. interaction energy, hydrogen bond energy, etc. Due to these factors, the proton oscillation in Zundel cation is shown to be nonmonotonic in nature with respect to the degree of confinement. Finally, we have demonstrated that the effect of confinement rendered by CNT(6,6) on Zundel cation can be the best suitable candidate among the series of CNTs considered in the present study, for assisting the proton transfer in the Zundel cation easily. These conclusions can have important implications and motivate further investigations to understand the fluidics under confined nanomaterials.

Density Functional Theory Study of Lithium Atom Adsorbing in the Interior and Exterior of a Series of Carbon Nanotubes

Density functional theory has been applied to study of adsorption of lithium atom in the interior and exterior of a series of carbon nanotubes. It is found that lithium atom can steadily adsorb in the interior and exterior of carbon nanotube. Lithium atom adsorbs at the center and near the sidewall for interior of carbon nanotube, but lithium atom only adsorbs near the sidewall for exterior of carbon nanotube. The interior of small diameter carbon nanotube is more favorable than larger ones for lithium atom adsorbing. This is because the lithium atom almost locates at the center of small diameter carbon nanotube, leading to strong interaction. Moreover, we also investigate the lithium atom of adsorption distance, Mulliken population and the system of the redistribution of electron density.

Shielding Effectiveness of CNTs/SSFs/PA6 Conductive Composites

A series of carbon nanotube (CNTs) and stainless steel fiber (SSFs) filled nylon 6 (PA6) conductive composites were synthesized for electromagnetic interference (EMI) shielding applications. The materials were prepared by the melt blending method with CNTs weight fraction of 1 and 3 wt% and SSFs of 2, 4, 6, 8, 10, and 12 wt%. The shielding effectiveness, electrical resistance and crystallization behaviors were measured. The results indicate that the shielding effectiveness and electrical properties can be improved by increasing either SSFs or CNTs contents. Higher content of CNTs can bring forward the percolation threshold and enhance the shielding effectiveness to 51.8 dB. Due to the nanoconfinement/multiple nucleation effects, PA6 crystallization behavior is influenced by adding the CNTs and SSFs.

Preparation of meso-macroporous carbon nanotube-alumina composite monoliths and their application to the preferential oxidation of CO in hydrogen-rich gases

A series of carbon nanotube (CNT)-alumina composite monoliths with meso-macroporous structures were successfully synthesized by imbibing macroporous monolithic polystyrene foams with carbon nanotube-alumina hydrosols. These composite monoliths possessed interconnected spherical macropores that mainly ranged in 10–40μm and adjustable mesopores of several nanometers. CNTs were uniformly dispersed throughout the alumina matrix. The CNT content and the calcination temperature markedly influenced the mesoporous structure, mechanical strength and thermal conductivity of the composite monoliths, but they did not significantly influence the phase transitions of alumina. The Pt-Ni/CNT-Al2O3 monoliths that were calcined at 1300°C exhibited high activity and selectivity with small Pt loading of 0.75wt.% for the preferential oxidation of CO. The residual concentration of CO was purified to less than 100ppm in the temperature range of 120–180°C in CO2 and water-containing hydrogen-rich gases at a volume space velocity of 10,400h−1. This type of composite monolith could potentially be used as a catalyst support for many different reactions.

First-principles study of alkali-atom doping in a series of zigzag and armchair carbon nanotubes

First-principles calculations are performed to study the Li doping in a series of carbon nanotubes with different diameters and chiralities. It is found that the Li–Li interaction inside or outside zigzag tubes is repulsive but strongly screened. Moreover, small diameter zigzag tubes are energetically more favorable than larger ones for Li doping. In contrast, almost all the armchair tubes have the same Li binding energy, especially for the outside doping. Our theoretical results suggest that small diameter zigzag tubes could be plausible candidates for Li-ion battery application. In addition, the doping of other alkali atoms in zigzag tubes is also investigated and the optimal binding distance between them are determined.

Fabrication and electrochemical activity of carbon nanotubes decorated with PtRu nanoparticles in acid solution

Abstract A series of carbon nanotubes (CNTs) decorated with bimetallic platinum/ruthenium nanocatalysts were fabricated to investigate their electrochemical activities in acid solution. These PtRu/CNT composites were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and N 2 physisorption. The crystalline size of PtRu nanocatalysts generally decreased with Ru atomic ratio, i.e., from 4.34 to 2.77 nm. The specific surface areas and pore size distributions of PtRu/CNT composites were slightly altered after the PtRu deposition. Cyclic voltammetry measurements in 1 M H 2 SO 4 showed that Pt 75 Ru 25 /CNT electrode has the greatest activity in electrochemical adsorption and desorption of hydrogen, i.e., the ratio of electrochemical surface coverage: 84.6%. This enhancement of electrochemical activity was attributed to two possible reasons: (i) addition of Ru in the bimetallic catalysts leads to reduce the required potential for water electrolysis and thus the associated carbon oxidation; (ii) the presence of Ru in the bimetallic alloys acts an important role in regenerating inactive Pt–CO ads sties.