Direct transition of potential of water droplets to electric energy using aligned single-walled carbon nanotubes

In this paper, we report that an electromotive force （EMF） can be induced in a rope of aligned single-walled carbon nanotubes （SWNTs） when water droplets fall on this rope. The magnitude of this EMF depends sensitively on the slant angle of the SWNTs. Most interestingly, both the magnitude and the direction of the induced EFM can be modulated by applying a current to the SWNTs. The concepts of electrical slip and no-slip are proposed and can be quantitatively described by ＂electrical slip resistance＂. This kind of generator does not need any magnet, rotor, etc and shows quite a different operating mechanism and design compared with a conventional large scale hydroelectric power generator.

Energy Absorption Characteristics of Single-walled Carbon Nanotubes

The excellent mechanical properties of carbon nanotubes make them potential candidates for engineering application. In this paper, the impact and failure behaviors of single-walled carbon nanotubes （SWCNTs） are investigated. The effects of diameter, length, and chirality on their energy absorption characteristics under lateral impact and axial crush are studied. By integrating the principle of molecular structural mechanics （MSM） into finite element method （FEM）, the locations and directions of fracture process can be predicted. It is shown that the specific energy absorption （SEA） of SWCNTs is 1-2 order of magnitude higher than that of the ordinary metallic materials and composites in axial impact, indicating that carbon nanotubes are promising energy absorption materials for engineering applications.

Water structures inside and outside single-walled carbon nanotubes under perpendicular electric field

The structures of water inside and outside （6,6）, （8,8）, and （10,10） single- walled carbon nanotubes （SWCNTs） under an electric field perpendicular to the tube axis are investigated by molecular dynamics simulations. The results show that dipole reorientation induced by electric field plays a significant role on the structures of confined water inside and outside SWCNTs. Inside SWCNTs, the average water occupancy and the average number of hydrogen bonds （H-bonds） per water molecule decrease as the electric intensity increases. Because the field intensity is sufficiently strong, the initial water structures inside the SWCNTs are destroyed, and the isolated water clusters are found. Outside SWCNTs, the azimuthal distributions of the density and the average number of H-bonds per water molecule around the solid walls become more and more asymmetric as the electric intensity increases. The percentages of water molecules involved in 0-5 H-bonds for all the three types of SWCNTs under different field intensities are displayed. The results show that those water molecules involved with most H-bonds are the most important to hold the original structures. When the electric field direction is parallel with the original preferred orientation, the density and the H-bond connections in water will be increased; when the electric field direction is perpendicular to the original preferred orientation, the density and the H-bond connections in water will be decreased.

A Self-supported Graphene/Carbon Nanotube Hollow Fiber for Integrated Energy Conversion and Storage

Wearable fiber-shaped integrated energy conversion and storage devices have attracted increasing attention,but it remains a big challenge to achieve a common fiber electrode for both energy conversion and storage with high performance.Here,we grow aligned carbon nanotubes(CNTs)array on continuous graphene(G)tube,and their seamlessly connected structure provides the obtained G/CNTs composite fiber with a unique self-supported hollow structure.Taking advantage of the hollow structure,other active materials(e.g.,polyaniline,PANI)could be easily functionalized on both inner and outer surfaces of the tube,and the obtained G/CNTs/PANI composite hollow fibers achieve a high mass loading(90%)of PANI.The G/CNTs/PANI composite hollow fibers can not only be used for high-performance fiber-shaped supercapacitor with large specific capacitance of 472 mF cm^-2,but also can replace platinum wire to build fiber-shaped dye-sensitized solar cell(DSSC)with a high power conversion efficiency of 4.20%.As desired,the integrated device of DSSC and supercapacitor with the G/CNTs/PANI composite hollow fiber used as the common electrode exhibits a total power conversion and storage efficiency as high as 2.1%.Furthermore,the self-supported G/CNTs hollow fiber could be further functionalized with other active materials for building other flexible and wearable electronics.

Research on the Relationship between Density of States and Conducting Properties of Single-walled Carbon Nanotubes

The analytical expression of the electronic density of states (DOS) for single-walled carbon nanotubes (SWNTs) has been derived on the basis of graphene approximation of the energy E(k) near the Fermi level EF. The distinctive properties of the DOS, the normalized differential conductivity and the current us bias for SWNTs are deduced and analyzed theoretically. The singularities in the DOS (or in the normalized differential conductivity) predict that the jump structure of current (or conductance)-bias of SWNTs exists. All conclusions from the theoretical analysis are in well agreement with the experimental results of SWNT's electronic structure and electronic transport. In other words, the simple theoretical model in this paper can be applied to understand a range of spectroscopic and other measurement data related to the DOS of SWNTs.

Detailed investigation on single water molecule entering carbon nanotubes

The behavior of a water molecule entering carbon nanotubes （CNTs） is stud- ied. The Lennaxd-Jones potential function together with the continuum approximation is used to obtain the van der Waals interaction between a single-walled CNT （SWCNT） and a single water molecule. Three orientations are chosen for the water molecule as the center of mass is on the axis of nanotube. Extensive studies on the variations of force, energy, and velocity distributions axe performed by vaxying the nanotube radius and the orientations of the water molecule. The force and energy distributions are validated by those obtained from molecular dynamics （MD） simulations. The acceptance radius of the nanotube for sucking the water molecule inside is derived, in which the limit of the radius is specified so that the nanotube is favorable to absorb the water molecule. The velocities of a single water molecule entering CNTs axe calculated and the maximum entrance and the interior velocity for different orientations axe assigned and compared.

Effect of hydrophobicity on the water flow in carbon nanotube-A molecular dynamics study

This work focuses on the study of the effect of hydrophobicity on the water flow in carbon nanotubes(CNTs)using a molecular dynamics(MD)approach for a wide range of potential applications such as water purification and high efficiency of nanofluid energy absorption systems(NEAS).The hydrophobicity between liquid water and surface of CNTs was characterized by interaction-energy-coefficient(IEC)—a parameter describing the energy interaction strength between water molecules and carbon atoms.It is shown that the static contact angles between water and carbon surface decrease from 155° to 44°when the values of IEC increase from 0.042 kJ/mol to 2.196 kJ/mol.In addition,the pressure drops in CNT became independent of IEC when the IEC value was higher than 1.192 kJ/mol for a given flow rate.It was found that the hydrophobicity of CNT surface has a significant impact on the pressure drop of water flow in the CNTs and MD method provides a quantitative evaluation of the impact.

Asymmetry of the water flux induced by the deformation of a nanotube

The behavior of nano-confined water is expected to be fundamentally different from the behavior of bulk water.At the nanoscale,it is still unclear whether water flows more easily along the convergent direction or the divergent one,and whether a hourglass shape is more convenient than a funnel shape for water molecules to pass through a nanotube.Here,we present an approach to explore these questions by changing the deformation position of a carbon nanotube.The results of our molecular dynamics simulation indicate that the water flux through the nanotube changes significantly when the deformation position moves away from the middle region of the tube.Different from the macroscopic level,we find water flux asymmetry（water flows more easily along the convergent direction than along the divergent one）,which plays a key role in a nano water pump driven by a ratchet-like mechanism.We explore the mechanism and calculate the water flux by means of the Fokker-Planck equation and find that our theoretical results are well consistent with the simulation results.Furthermore,the simulation results demonstrate that the effect of deformation location on the water flux will be reduced when the diameter of the nanochannel increases.These findings are helpful for devising water transporters or filters based on carbon nanotubes and understanding the molecular mechanism of biological channels.

Coupling N-doping and confined Co_(3)O_(4) on carbon nanotubes by polydopamine coating strategy for pleiotropic water purification

The development of effective and sustainable solutions for pleiotropic water purification becomes urgent and attractive.Heterogeneous Fenton-like catalysts for activation of peroxymonosulfate(PMS)to purify organic wastewater show great promise.In this work,by tuning metal loading with an in-situ polydopamine coating strategy,oxygen vacancy-enriched Co_(3)O_(4) loading on N-doped carbon nanotubes(CNTs)were constructed to enhance PMS activation efficiency for pollutants degradation.Impressively,the obtained modified CNTs afford a well-developed N-containing network structure,which is further endowed with abundant Co(Ⅱ)/Co(Ⅲ)redox cycles and significant metal-carbon interactions.In particular,the surface N doping in CNTs might induce the oriented enrichment of pollutants around the catalyst,which reduces the migration distance and correspondingly improves the utilization of reactive oxidative species.The electron transfer efficiency of the catalyst can be further improved by incorporating oxygen vacancy-enriched Co_(3)O_(4).The performance results show that the optimal NC/Co-1 could mineralize 20×10^(-6)of bisphenol A(BPA)by almost 98%in 8 min.A low reaction activation energy(26.05 kJ·mol^(-1))in BPA degradation was demonstrated by the NC/Co-1.More importantly,NC/Co-1 can inherit excellent degradation performance towards oxytetracycline,2,4-dichlorophenol,and tetracycline,showing wide practical flexibility.In addition,by virtue of the photothermal conversion property,NC/Co-1 achieves an additive function for interfacial solar water evaporation(1.84 kg·m^(-2)·h^(-1),112.51%),showing impressive potential for clean water recovery under complicated environmental pollution conditions.

Recent progresses on the new condensed forms of single-walled carbon nanotubes and energy-harvesting devices

We demonstrate an effective method to prepare a new condensed form of single-walled carbon nanotubes(crystal of SWNTs) using a series of diamond wire drawing dies.X-ray diffraction indicates that the SWNTs form a two-dimensional triangular lattice with a lattice constant of 19.62 ?.An intertube spacing of 3.39 ? of between adjacent SWNTs results in a sharp(002) reflection in the X-ray diffraction pattern.Meanwhile,we developed an approach based on the Coulomb explosion to separate SWNTs from their bundle.The separated SWNTs have a typical length of several microns and form a nanotree at one end of the original bundle.The separation is convenient and involves no surfactant.In studying devices comprising SWNTs,we find that a four-probe technique can be employed to study the filling of and flow within the inner channel of an individual SWNT.Current/voltage can drive water molecules to have directional flow along an SWNT,and the flowing of water inside an SWNT can induce a voltage gradient force(an induced electromotive force) along the SWNT.This energy conversion is realized by the mutual coupling of water dipoles and charge carriers present in SWNTs.The results suggest that SWNTs can be exploited as molecular channels for water and may find potential application in nanoscale energy conversion.Moreover,a surface-energy generator comprising SWNTs was demonstrated to harvest the surface energy of ethanol.The performance(the induction rate for Voc,the value of Voc and the output power) can be significantly enhanced by the Marangoni effect.

Metal-organic framework and carbon hybrid nanostructures:Fabrication strategies and electrocatalytic application for the water splitting and oxygen reduction

With the rapid development of economy,the increasing energy crisis and environmental pollution urge us to develop sustainable and clean novel energy systems.Among them,the electrochemical energy conversion technology is considered as one of the ideal potential alternative energy systems,and the electrocatalysts play critical roles but are still challenging.Metal-organic frameworks(MOFs),thanks to their regular channels,atomically dispersed active centers,adjustable chemical and pore environments,have severed as promising electrocatalysts for electrochemical energy conversion.However,the relatively low conductivities and instabilities of MOFs limit their wide application in this field.In this case,fabricating hybrids of MOFs and carbon-based materials is an effective way to overcome above deficiencies.In addition,the synergistic effects between MOFs and carbons could optimize the electronic structures of active sites and promote the active surface areas,and thus improve the electrocatalytic performances of the composites.Herein,we outline the current development of MOF/carbon composites,including the fabrication methods of MOFs hybridized with various dimensions of carbon-based materials and the electrocatalysis utilization for water splitting,including the hydrogen evolution reaction(HER),oxygen evolution reaction(OER),and the oxygen reduction reaction(ORR).Finally,the advantages and challenges of such catalysts are highlighted and future endeavors on the development of MOF/carbon composites for the HER,OER and ORR are discussed.

Conversion of Solar Energy to Fuels by Inorganic Heterogeneous Systems

Over the last several years,the need to find clean and renewable energy sources has increased rapidly because current fossil fuels will not only eventually be depleted,but their continuous combustion leads to a dramatic increase in the carbon dioxide amount in atmosphere.Utilisation of the Sun's radiation can provide a solution to both problems.Hydrogen fuel can be generated by using solar energy to split water,and liquid fuels can be produced via direct CO2 photoreduction.This would create an essentially free carbon or at least carbon neutral energy cycle.In this tutorial review,the current progress in fuels' generation directly driven by solar energy is summarised.Fundamental mechanisms are discussed with suggestions for future research.

A Single-Step Process for Preparing Supercapacitor Electrodes from Carbon Nanotubes

This paper introduces an easy single-step process for preparing the supercapacitor electrode from carbon nanotubes (CNTs) which were directly grown on a nickel foam framework by a chemical vapor deposition (CVD) technique. Due to the hierarchical porous structure and robust CNT-metal contacts, the present electrode exhibits better capacitive performance and lower internal resistance than the regular transfer method. Its specific capacitance of 25 F/g is 127 % higher than the value of the electrode prepared by the transfer method. This work proposes a simple, effective and eco-nomical approach for preparing a supercapacitor electrode without additional catalysts and pre- or post-treatments.

Photocatalytic overall water splitting by graphitic carbon nitride

Photocatalytic overall water splitting(OWS)without using any sacrificial reagent to realize H_(2)and O_(2)production in the stoichiometric ratio of 2:1 is viewed as the“holy grail”in the field of solar fuel production.Developing stable,low cost,and nontoxic photocatalysts that have satisfactory solar-tohydrogen conversion efficiency is of significance but challenging for realizing the large-scale use of this sustainable technology.Among various photocatalysts,graphitic carbon nitride(GCN)has shown great potential as an ideal candidate to fulfill the breakthrough in this dynamic research field due to its attractive physicochemical properties.Herein,for the first time,the state-ofthe-art research progress of GCN for photocatalytic OWS is reviewed.We first summarize the basic principle of photocatalytic OWS along with the advantages/challenges of GCN introduced.The strategies that have been used to modulate the OWS activity of GCN are then reviewed,including cocatalyst investigation,morphology modulation,atomic structure modification,crystallinity engineering,and heterostructure construction.Toward the end of the review,the concluding remarks and perspectives for the future development are presented,with our expectation to provide some new ideas for the design of advanced OWS photocatalysts.

Three dimensional carbon substrate materials for electrolysis of water

Water splitting is an important approach for energy conversion to obtain hydrogen and oxygen. Apart from solar water splitting, electrochemical method plays a key role in the booming field, and it is urgent to develop novel and efficient catalysts to accelerate water splitting reaction. Recently, newly emerging self-supported materials, especially three dimensional（3D） carbon substrate electrochemical catalysts, have attracted great attention benefiting from their fantastic catalytic performances, such as large surface area,enhanced conductivity, tunable porosity, and so on. This review summarizes the outstanding materials used for hydrogen evolution reaction and oxygen evolution reaction. And catalysts that acted as both anode and cathode in two-electrode systems for overall water splitting are introduced systematically. The opportunities and challenges of 3D carbon substrate materials for electrochemical water splitting are proposed.

Single-wall carbon nanotube assisted all-optical wavelength conversion at 2.05μm

We fully demonstrate the special requirements of a mid-infrared all-optical wavelength converter.The construction mechanism of a 2.05μm all-optical wavelength converter based on the single-wall carbon nanotube[SWCNT]is proposed.Systematic experiments are carried out,and the converter device is successfully developed.With the assistance of SWCNT-coated microfiber,the conversion efficiency up to-45.57 d B is realized,and the tuning range can reach9.72 nm.The experimental results verify the correctness of the proposed mechanism and the feasibility of the converter device so that it can be a new technical approach for all-optical wavelength conversion beyond 2μm.We believe the research can extend the application of this composite waveguide in the field of all-optical communication.

碳科学技术的研究现状与发展趋势--记Carbon 2010国际碳会议

The annual world conference on carbon,Carbon 2010,was held in Clemson,USA,July 11-16,2010,and was hosted by the American Carbon Society,Clemson University,and Center for Advanced Engineering Fibers and Films.About 410 attendees from 35 countries participated in the conference,and 510 papers were accepted for presentation,including 4 plenary lectures,5 award lectures,32 keynote lectures,214 oral presentations,and 255 posters,involving 12 topics,namely,graphenes,nanotubes and fullerenes,precursor synthesis and characterization,conversion processes,microstructure and properties,molecular modeling,novel experimental measurements,electronics and sensors,fibers and composites,biology and medicine,environment and safety,energy storage and generation,and other novel uses.Graphene-based materials,molecular simulation of porous carbon,carbon science at the interface with biological systems,and neutron irradiation damage in graphite were the subjects of the plenary lectures.Studies on nanocarbons are quite active,in particular,in the field of carbon nanotubes and graphene,and rapid progress has been made in the electrochemical properties,energy conversion and energy storage applications of these carbon materials.

二硫化钼和碳纳米管复合物电极用于盐差能转换

海洋占地球水资源总量的97%,地表面积的70%以上。随着化石燃料等不可再生能源的持续消耗与可再生能源的快速发展,人们对海洋资源的利用越来越重视。海洋能包括潮汐能、波浪能、温差能和盐差能等。其中盐差能是海水和淡水相互作用产生的能量,是以化学能形式存在的海洋能,这种能量较多产生在河口处。目前,压力延迟渗透技术、反电渗析技术和电容混合技术是转换盐差能的三种主要技术。本文构建了一种基于电容混合技术的新型盐差电池,使用二硫化钼和多壁碳纳米管复合物电极作为阳极,活性炭作为阴极。将两种不同离子储存机制的材料复合在一起,二硫化钼具有类似石墨烯的层状结构,层间间距约为石墨烯的两倍,是一种可以与钠离子发生插层反应的电池电极材料。多壁碳纳米管具有典型的双电层效应,放电时在其表面吸附钠离子的同时,可以帮助钠离子更快地进入二硫化钼层间,加快离子传输效率和盐差能的转换效率。对该复合材料进行物理和电化学表征,并与活性炭电极组装的盐差电池,测试其盐差能转换能力。浓度响应电压150 mV,经过一个完整的四步循环后,转换能量密度可达6.96 J·g^(-1)。该器件原材料价格较低,并且不使用离子膜,更加环保,为转换盐差能的研究提供了一种新途径。

Synthetic Strategies of Carbon Nanobelts and Beyond

Carbon nanobelts(CNBs)with aesthetically appealing molecular structures and outstanding physical properties have attracted more and more attentions from the scientific community due to their potential applications in synthetic materials,host-guest chemistry,optoelectronics,and so on.The synthesis of CNBs at different stages was overviewed and some representative breakthroughs and advances in synthetic strategies were highlighted and discussed.The key issue for the synthesis of CNBs is how to construct curved structures with high strain energy.We not only proposed a few unconventional CNBs as the promising target molecules,but also pointed out the bottom-up synthesis of conjugated tubular segments of carbon nanotubes sharing similar properties as carbon nanotubes is the next focus in this emerging area.

用于水处理的光热转换碳材料的制备及应用进展

太阳能光热蒸发是实现水体处理的一种高效绿色技术,近年来受到了研究者们的密切关注。碳材料因具有宽光谱吸收能力和良好的光热性能,被认为是理想的太阳能光热转换材料。首先概述了光热转换碳材料及其光热转换原理,简要阐述了基于碳材料的太阳能蒸发系统的结构设计;重点介绍了应用于水处理领域的碳材料的制备方法;总结了光热转换碳材料在海水淡化、废水处理的应用现状;对水处理用光热转换碳材料的未来研究方向及发展进行了展望。可为光热转换碳材料在水处理领域应用的研究和发展提供一定的策略支撑。