Synergistic effect of carbon nanotube and encapsulated carbon layer enabling high-performance SnS_2-based anode for lithium storage

Tin disulfide(SnS_(2)),due to large interlayer spacing and high theoretical capacity,is regarded as a prospective anode material for lithium-ion batteries.Nevertheless,the poor electron conductivity of SnS_(2) and huge volumetric change during the lithiation/delithiation process lead to a rapid capacity decay of the battery,hindering its commercialization.To address these issues,herein,SnS_(2) is in-situ grown on the surface of carbon nanotubes(CNT)and then encapsulated with a layer of porous amorphous carbon(CNT/SnS_(2)@C)by simple solvothermal and further carbonization treatment.The synergistic effect of CNT and porous carbon layer not only enhances the electrical co nductivity of SnS_(2) but also limits the huge volumetric change to avoid the pulverization and detachment of SnS_(2).Density functional theo ry calculations show that CNT/SnS_(2)@C has high Li^(+)adsorption and lithium storage capacity achieving high reaction kinetics.Consequently,cells with the CNT/SnS_(2)@C anode exhibit a high lithium storage capacity of 837mAh/g after 100 cycles at 0.1 A/g and retaining a capacity of 529.8 mAh/g under 1.0 A/g after 1000 cycles.This study provides a fundamental understanding of the electrochemical processes and beneficial guidance to design high-performance SnS_(2)-based anodes for LIBs.

Hollow tubes constructed by carbon nanotubes self-assembly for CO_(2) capture

Carbon nanotubes(CNTs)have garnered significant attention in the fields of science,engineering,and medicine due to their numerous advantages.The initial step towards harnessing the potential of CNTs involves their macroscopic assembly.The present study employed a gentle and direct self-assembly technique,wherein controlled growth of CNT sheaths occurred on the metal wire’s surface,followed by etching of the remaining metal to obtain the hollow tubes composed of CNTs.By controlling the growth time and temperature,it is possible to alter the thickness of the CNTs sheath.After immersing in a solution containing 1 g/L of CNTs at 60℃ for 24 h,the resulting CNTs layer achieved a thickness of up to 60μm.These hollow CNTs tubes with varying inner diameters were prepared through surface reinforcement using polymers and sacrificing metal wires,thereby exhibiting exceptional attributes such as robustness,flexibility,air tightness,and high adsorption capacity that effectively capture CO_(2) from the gas mixture.

Nitrogen-doped carbon encapsulated in mesoporous TiO2 nanotubes for fast capacitive sodium storage

Controllable synthesis of insertion-type anode materials with beneficial micro-and nanostructures is a promising approach for the synthesis of sodium-ion storage devices with high-reactivity and excellent electrochemical performance.In this study,we developed a sacrificial-templating route to synthesize TiO_(2)@N-doped carbon nanotubes(TiO_(2)@NC-NTs)with excellent electrochemical performance.The asprepared mesoporous TiO_(2)@NC-NTs with tiny nanocrystals of anatase TiO_(2) wrapped in N-doped carbon layers showed a well-defined tube structure with a large specific surface area of 198 m^(2) g^(-1) and a large pore size of~5 nm.The TiO_(2)@NC-NTs delivered high reversible capacities of 158 m A h g^(-1) at 2 C(1 C=335 m A g^(-1))for 2200 cycles and 146 m A h g^(-1) at 5 C for 4000 cycles,as well as an ultrahigh rate capability of up to 40 C with a capacity of 98 m A h g^(-1).Even at a high current density of 10 C,a capacity of 138 m A h g^(-1) could be delivered over 10,000 cycles.Thus,the synthesis of mesoporous TiO_(2)@NC-NTs was demonstrated to be an efficient approach for developing electrode materials with high sodium storage and long cycle life.

Effects of Potassium and Manganese Promoters on Nitrogen-Doped Carbon Nanotube-Supported Iron Catalysts for CO_2 Hydrogenation

Nitrogen-doped carbon nanotubes （NCNTs） were used as a support for iron （Fe） nanoparticles applied in car- bon dioxide （CO_2） hydrogenation at 633 K and 25 bar （1 bar = 10-5 Pa）. The Fe/NCNT catalyst promoted with both potassium （K） and manganese （Mn） showed high performance in CO_2 hydrogenation, reaching 34.9% conversion with a gas hourly space velocity （GHSV） of 3.1 L-（g·h）-1. Product selectivities were high for olefin products and low for short-chain alkanes for the K-promoted catalysts. When Fe/NCNT catalyst was promot- ed with both K and Mn, the catalytic activity was stable for 60 h of reaction time. The structural effect of the Mn promoter was demonstrated by X-ray diffraction （XRD）, temperature-programmed reduction （TPR） with molecular hydrogen （H2）, and in situ X-ray absorption near-edge structure （XANES） analysis. The Mn pro- moter stabilized wtistite （FeO） as an intermediate and lowered the TPR onset temperature. Catalytic ammo- nia （NH_3） decomposition was used as an additional probe reaction for characterizing the promoter effects. The Fe/NCNT catalyst promoted with both K and Mn had the highest catalytic activity, and the Mn-promoted Fe/NCNT catalysts had the highest thermal stability under reducing conditions.

Nickel nanoparticles supported on nitrogen-doped carbon nanotubes are a highly active,selective and stable CO_(2) methanation catalyst

CO_(2) methanation using nickel-based catalysts has attracted large interest as a promising power-to-gas route.Ni nanoparticles supported on nitrogen-doped CNTs with Ni loadings in the range from 10 wt% to 50 wt% were synthesized by impregnation,calcination and reduction and characterized by elemental analysis,X-ray powder diffraction,H_(2) temperature-programmed reduction,CO pulse chemisorption and transmission electron microscopy.The Ni/NCNT catalysts were highly active in CO_(2) methanation at atmospheric pressure,reaching over 50% CO_(2) conversion and over 95% CH_(4) selectivity at 340℃ and a GHSV of50,000 mL g^(-1) h^(-1) under kinetically controlled conditions.The small Ni particle sizes below 10 nm despite the high Ni loading is ascribed to the efficient anchoring on the N-doped CNTs.The optimum loading of 30 wt%-40 wt% Ni was found to result in the highest Ni surface area,the highest degree of conversion and the highest selectivity to methane.A constant TOF of 0.3 s^(-1) was obtained indicating similar catalytic properties of the Ni nanoparticles in the range from 10 wt%to 50 wt% Ni loading.Long-term experiments showed that the Ni/NCNT catalyst with 30 wt% Ni was highly stable for 100 h time on stream.

Robust S-doped TiO_(2)@N,S-codoped carbon nanotube arrays as free-binder anodes for efficient sodium storage

Titanium dioxide(TiO_2) has been investigated broadly as a stable,safe,and cheap anode material for sodium-ion batteries in recent years.However,the poor electronic conductivity and inherent sluggish sodium ion diffusion hinder its practical applications.Herein,a self-template and in situ vulcanization strategy is developed to synthesize self-supported hybrid nanotube arrays composed of nitrogen/sulfur-codoped carbon coated sulfur-doped TiO_2 nanotubes(S-TiO_2@NS-C) starting from H_2 Ti_2 O_5-H_2 O nanoarrays.The S-TiO_2@NS-C composite with one-dimensional nano-sized subunits integrates several merits.Specifically,sulfur doping strongly improves the Na~+ storage ability of TiO_2@C-N nanotubes by narrowing the bandgap of original TiO_2.Originating from the nanoarrays structures built from hollow nanotubes,carbon layer and sulfur doping,the sluggish Na~+ insertion/extraction kinetics is effectively improved and the volume variation of the electrode material is significantly alleviated.As a result,the S-TiO_2@NS-C nanoarrays present efficient sodium storage properties.The greatly improved sodium storage performances of S-TiO_2@NS-C nanoarrays confirm the importance of rational engineering and synthesis of hollow array architectures with higher complexity.

Synthesis and evaluation of carbon nanotubes composite adsorbent for CO2 capture： a comparative study of CO2 adsorption capacity of single-walled and multi-walled carbon nanotubes

As a preliminary investigation towards obtaining carbon nanotube composite adsorbent for CO2 capture, in this study CO2 adsorption performance of three commercial carbon nanotubes （CNTs） one single-walled carbon nanotubes （SWCNTs）, and two （2） different multi-walled carbon nanotubes （referred to as A-MWCNTs and B-MWCNTs） were evaluated and compared. The purpose of this study was to compare the different types of CNTs and select the best to serve as the solid anchor in the development of a hydrophobic composite adsorbent material for CO2 capture. The N2 physi- sorption of the CNTs was conducted to determine their surface area, pore volume and pore size. In addition, morphology and purity of the CNTs were checked with Transmission Electron Microscopy and Raman Spectroscopy, respectively. The CO2 adsorption capacity of the CNTs was evaluated using Thermo-gravimetric analysis （TGA） at 1.1 bar, at operating temperature ranged from 25 to 55 ~C and at different CO2 feed flow rates, in order to evaluate the effects of these variables on the CO2 adsorption capacity. The results of CO2 adsorption with the TGA show that CO2 adsorption capacity for both SWCNTs and MWCNTs was the highest at 25 ~C. Changing the CO2 flowrates had no significant effect on the adsorption capacity of MWCNTs, but decreasing the CO2 flow rate resulted in the enhancement of the CO2 adsorption capacity of SWCNTs. Overall, it was found that the SWCNTs displayed the highest CO2 adsorption capacity （29.97 gCO2/kg ad- sorbent） when compared to the MWCNTs （12.09 gCO2/kg adsorbent）, indicating a 150% increase in adsorption capacity over MWCNTs.

A Bi-layer Composite Film Based on TiO_2 Hollow Spheres, P25,and Multi-walled Carbon Nanotubes for Efficient Photoanode of Dye-sensitized Solar Cell

A bi-layer photoanode for dye-sensitized solar cell(DSSC) was fabricated, in which TiO_2 hollow spheres(THSs) were designed as a scattering layer and P25/multi-walled carbon nanotubes(MWNTs) as an under-layer. The THSs were synthesized by a sacrifice template method and showed good light scattering ability as an over-layer of the photoanode. MWNTs were mixed with P25 to form an under-layer of the photoanode to improve the electron transmission ability of the photoanode. The power conversion efficiency of this kind of DSSC with bi-layer was enhanced to 5.13 %,which is 14.25 % higher than that of pure P25 DSSC.Graphical Abstract A bi-layer composite photoanode based on P25/MWNTs-THSs with improved light scattering and electron transmission, which will provide a new insight into fabrication and structure design of highly efficient dyesensitized solar cells.

Growth of carbon nanotubes on the novel FeCo-Al_2O_3 catalyst prepared by ultrasonic coprecipitation

FeCo-Al2O3 catalyst was prepared by an ultrasonic coprecipitation （UC） method for the growth of carbon nanotubes （CNTs） from catalytic decomposition of methane.Its catalytic performance was compared with that of the FeCo-Al2O3 catalyst counterparts prepared by stepwise impregnation （I） and conventional coprecipitation （C） methods,respectively.The structure and properties of the catalysts and the CNTs as produced thereon were investigated by means of XRD,XPS,TEM and N2 adsorption techniques.It was found that the catalyst prepared by the ultrasonic coprecipitation method was more active,and the yield and purity of the synthesized CNTs were promoted evidently.The XPS results revealed that there were more active components on the surface of the catalyst prepared by the ultrasonic coprecipitation method.On the other hand,N2 adsorption demonstrated that the catalyst prepared by the ultrasonic coprecipitation method conferred larger specific surface area,which was beneficial to dispersion of active components.TEM images further confirmed its higher dispersion.These factors could be responsible for its higher activity for the growth of CNTs from catalytic decomposition of methane.

Growth of Carbon Nanotubes over Ni Nano-particles Prepared in Situ by Reduction of La_2NiO_4 Oxides

A novel catalyst precursor, La2NiO4, was investigated to synthesize carbon nanotubes,obtained from catalytic disproportionation of CO. The morphology of carbon nanotubes has been examined by TEM (transmission electron micrograph) and SEM (scaning electron micrograph). It was observed that the Ni nano-particle size formed at different reducing temperatures was a key factor to the yield and diameter of carbon nanotubes.

Photocatalytic Oxidation of Low Molecular Weight Hydrocarbon Gases over Pt-TiO2 Nanotubes

Pt-TiO2 nanotubes with tube diameter of -120 nm and uniformly dispersed Pt particles（size of -2 nm） were successfully synthesized via a carbon nanotube（CNT） templating method followed by a photo-deposition processing of Pt nanoparticles. The as-obtained Pt-TiO2 NTs possess both enhanced visible light absorption and reduced recombination of photogenerated electrons and holes. These merits boost the Pt-TiO2 NTs an excellent photocatalytic material toward photooxidation of a variety of low molecular hydrocarbons under atmospheric environment.

Carbon Nanotube Coating on Titanium Substrate Modified with TiO_2 Nanotubes

A combination of carbon nanotubes （CNTs） and titanium （Ti） modified with TiO2 nanotubes （TiO2 NTs） was fulfilled with the aim of improving bioactivity of Ti implant.First,well-ordered TiO2 NTs were prepared by the electrochemical anodization of Ti in an ethylene glycol electrolyte containing 1 wt% NH4F and 10 wt% H2O at 20 V for 50 min,followed by annealing.Then,the carboxylated CNTs were coated onto the TiO2 NTs using electrophoretic deposition （EPD） technique.The growth of hydroxyapatite （HA） on the samples was investigated by soaking them in simulated body fluid （SBF）.The result showed the CNTs-coated Ti with the modification of TiO2 NTs （CNTs-TiO2 NTs） was more efficient to induce HA formation than the CNTs-coated smooth Ti （CNTs-Ti）.The vitro cell response was evaluated using osteoblast cells （MC3T3-E1）.The good cell proliferation and strong cell adhesion could be obtained on the CNTs-TiO2 NTs.These results indicated that CNT coating on the Ti modified with TiO2 NTs could be potentially useful for the periodontal ligament combination on dental implants.

A parametric study of methane decomposition into carbon nanotubes over 8Co-2Mo/Al_2O_3 catalyst

The effects of reaction temperature, partial pressure of methane, catalyst weight and gas hourly space velocity （GHSV） on methane decomposition were reported. The decomposition reaction was performed in a vertical fixed-bed reactor over 8Co-2Mo/Al 2 O 3 catalyst. The experimental results show that these four process parameters studied had vital effects on carbon yield. As revealed by the electron microscopy and Raman spectroscopy analyses, the reaction temperature and GHSV governed the average diameter, the diameter distribution and the degree of graphitization of the synthesized carbon nanotubes （CNTs）. Also, an evidence is presented to show that higher temperatures and higher GHSV favored the formation of better-graphitized CNTs with larger diameters.

NH_2 Ion Implantations Induced Superior Cell Attachment of Carbon Nanotubes

Objective： Cell and platelet attachment on the multiwalled carbon nanotubes （MWCNTs） were studied by ion implantation. Methods： NH2 ion implantation was performed at the energy of 30 keV with the fluence of 1 x 1016 ions/era2 at room temperature. Results： The cell attachment tests showed interesting results in that the number of the platclets adhering on the surface of the MWCNTs was reduced significantly after NH2 ion implantation, whereas, mouse fibroblast cells （L929） cultured on NH2 ion implanted MWCNTs displayed higher cell-viability, proliferation, and stretching compared with MWCNTs. Conclusion： No appreciable change in the tensile strength and the optical transmittance of the implanted samples was observed. X-ray photoelectron spectroscopy （XPS） analysis showed that NH2 ion implantation caused the formation of new N-containing groups.

Effects of B and N dopings and H_2O adsorption on structural stability and field emission properties of cone-capped carbon nanotubes

The effects of B and N dopings and H2O adsorption on the structural stability and the field emission properties of cone-capped carbon nanotubes （CCCNTs） were investigated by using the density-functional theoretical calculation. The adsorption of H2O can increase the structural stability and decrease the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital （HOMO-LUMO gap） of the CCCNTs. The strength of total electric field on the top of the H2O-adsorbed CCCNTs is larger than that of the B-doped and the N-doped CCCNTs, electrons will be emitted primarily from the H2O-adsorbed CCCNTs at the same applied voltage. Therefore, the H2O adsorption can lower the threshold voltage for the CCCNTs. While the B and the N dopings produce opposite effects. The HOMO-LUMO gap of the N-doped CCCNTs is the widest among all the gaps of the CCCNTs.

MgO-decorated carbon nanotubes for CO_2 adsorption:first principles calculations

The global greenhouse effect makes it urgent to deal with the increasing greenhouse gases. In this paper the performance of MgO-decorated carbon nanotubes for CO2 adsorption is investigated through first principles calculations. The results show that the MgO-decorated carbon nanotubes can adsorb CO2 well and are relatively insensitive to O2 and N2 at the same time. The binding energy arrives at 1.18 eV for the single-MgO-decorated carbon nanotube adsorbing one CO2 molecule, while the corresponding values for O2 and N2 are 0.55 eV and 0.06 eV, respectively. In addition, multi-molecule adsorption is also proved to be very satisfactory. These results indicate that MgO-decorated carbon nanotubes have great potential applications in industrial and environmental processes.

Behaviour of Ru(bpy)_²⁺3on the Surface of Water-Soluble Single-Walled Carbon Nanotubes on Adding Other Cations

Behaviour of excited Ru(bpy)2+3 bound to the surface of water-soluble single-walled carbon nanotubes on addition of other cations have been investigated by measuring Ru(bpy) luminescence. In contrast to what was observed with a solution containing rod-like aggregation particles of Nafion, we found that Ru(bpy)2+3 has a stronger attraction than that of other cations to the sulfonic groups on the carbon nanotubes. Such a difference is attributed to the unique micro-environmental characteristics of the molecular assemblies.

Enhanced Photoelectrochemical Property of Zn Loaded TiO2 Nanotube Arrays Electrode

TiO2 nanotube arrays （TNTs） electrode loaded with Zn nanoparticles was prepared by anodization and the size of Zn nanoparticle loaded on TNTs electrode was controlled by chronoamperometry deposition time. Results of SEM and XRD analysis show that Zn nanoparticles had a diameter of about 15-25 nm when the deposition time was 3-5 s. The UV-Vis diffuse reflectance spectra show the Zn loaded harvest light with 480-780 nm more effectively than the unloaded sample. The photocurrent response of Zn loaded TNTs electrodes were studied, the results showed that TNTs electrodes loaded with Zn nanoparti-cles has 50% increased photocurrent response under high-pressure mercury lamp irradiation compared with unloaded TNTs electrode.

Removal of Lead Ions from Wastewater Using Functionalized Multiwalled Carbon Nanotubes with Tris(2-Aminoethyl)Amine

Recently, many attempts have been made to use carbon nanotubes in analytical chemistry, especially in adsorption of heavy metal ions from water. In this study, multiwalled carbon nanotubes (MWCNTs) were functionalized with tris(2-aminoethyl) amine. The functionalized nanoparticles were characterized using Fourier transform infrared (FTIR), thermal gravimetric analyzer (TGA), elemental analysis, and Raman spectroscopy. The results revealed that the functionalization reaction was successfully accomplished. Lead adsorption from water was carried out using functionalized MWCNTs and measured by flame atomic absorption spectrometry (FAAS). The effects of pH, shaking time, initial metal ion concentration, and adsorbent dosage on the adsorption process were studied via batch method. The results obtained showed that removal of lead ions strongly depended on the pH. Desorption study revealed that lead ions adsorbed on the functionalized MWCNTs could be desorbed at pH 3 due to breakage of complexes formed on the sorbent surface. Maximum adsorption capacity of the sorbent under the optimal conditions was 43 mg/g. This favorable adsorption capacity suggests that functionalized carbon nanotubes can be applied for removal of lead from water solutions. The data obtained were fitted with the Langmuir and Freundlich isotherm adsorption models and Langmuir model showed better agreement with the experimental data.

Binary molten salt in situ synthesis of sandwich-structure hybrids of hollowβ-Mo2C nanotubes and N-doped carbon nanosheets for hydrogen evolution reaction

Focused exploration of earth-abundant and cost-efficient non-noble metal electrocatalysts with superior hydrogen evolution reaction(HER)performance is very important for large-scale and efficient electrolysis of water.Herein,a sandwich composite structure(designed as MS-Mo2C@NCNS)ofβ-Mo2C hollow nanotubes(HNT)and N-doped carbon nanosheets(NCNS)is designed and prepared using a binary NaCl–KCl molten salt(MS)strategy for HER.The temperature-dominant Kirkendall formation mechanism is tentatively proposed for such a three-dimensional hierarchical framework.Due to its attractive structure and componential synergism,MS-Mo2C@NCNS exposes more effective active sites,confers robust structural stability,and shows significant electrocatalytic activity/stability in HER,with a current density of 10 mA cm-2 and an overpotential of only 98 mV in 1 M KOH.Density functional theory calculations point to the synergistic effect of Mo2C HNT and NCNS,leading to enhanced electronic transport and suitable adsorption free energies of H*(ΔGH*)on the surface of electroactive Mo2C.More significantly,the MS-assisted synthetic methodology here provides an enormous perspective for the commercial development of highly active non-noble metal electrocatalysts toward efficient hydrogen evolution.