Bimetallic selenide heterostructure with directional built-in electricfield confined in N-doped carbon nanofibers for superior sodium storage with ultralong lifespan

Constructing heterostructure is considered as an effective strategy to address the sluggish electronic and ionic kinetics of anode materials for sodium ion batteries(SIBs).However,realizing the orientated growth and uniform distribution of the heterostructure is still a great challenge.Herein,the regulated novel CoSe2/NiSe2 heterostructure confined in N-doped carbon nanofibers(CoSe₂/NiSe₂@N-C) are prepared by using Co/Ni-ZIF template,in which,the CoSe₂/NiSe_2...     

Tempura-like carbon/carbon composite as advanced anode materials for K-ion batteries

Graphite as a promising anode candidate of K-ion batteries (KIBs) has been increasingly studied currently,but corresponding rate performance and cycling stabili...     

Structure and surface modification of MXene for efficient Li/K-ion storage

In this paper, three-dimensional(3D) hollow Ti₃C₂T_x MXene tubes(HTCTs) with more –O terminal groups and fewer –F groups are successfully prepared via the template-oriented electrostatic self-assembly and the subsequent annealing treatment. The obtained 3D hollow structure with large specific surface area,unique porous structure, and enlarged interlayer spacing could prevent the re-stacking of twodimensional(2D) sheets and shorten the diffusion pathway of ions. Fu...     

Electrospinning techniques for Li,Na and K-ion batteries

In this current outlook, we critically review the most vital new outcomes in the field of rechargeable Li, Na and K-ion batteries. We deliberate current discoveries like the progress of electrospinning and their applications in future. Mainly, we discuss freestanding and binder-free electrodes structural and morphological effect when it undergoes long term cycling. Finally, this short review grants the up-to-date advancement on novel processing strategies of various carbon-based electrospun composites as anodes whose performance are similar with or even can beat that of the commercial anode material system.     

Single-walled carbon nanotubes embedded in oriented polymeric nanofibers by electrospinning

The electrospinning process was used successfully to embed single-walled carbon nanotubes (SWCNTs) in a poly(ethylene oxide) (PEO) matrix, forming composite nanofibers. Initial dispersion of SWCNTs in water was achieved by the use of an amphiphilic alternating copolymer of styrene and sodium maleate. The resulting dispersions were stable, having a dark, smooth, ink-like appearance. For electrospinning, the dispersions were mixed with PEO solution in an ethanol/water mixture. The distribution and conformation of the nanotubes in the nanofibers were studied by transmission electron microscopy (TEM). Oxygen plasma etching was used to expose the nanotubes within the nanofibers to facilitate direct observation. Nanotube alignment within the nanofibers was shown to depend strongly on the quality of the initial dispersions. Well-dispersed and separated nanotubes were embedded in a straight and aligned form, while entangled nonseparated nanotubes were incorporated as dense aggregates. X-ray diffraction demonstrated a high degree of orientation of the PEO crystals in the electrospun nanofibers with embedded SWCNTs. This result is in pronounced distinction to the detrimental effect of incorporation of multiwalled carbon nanotubes on polymer orientation in electrospun nanofibers, as reported previously.     

Electrospun CoSe@N-doped carbon nanofibers with highly capacitive Li storage

One-dimensional nano-structured materials have attracted attention due to its unique properties afforded such as the across-linked structures and large aspect ratios.In this work,one-dimensional CoSe@N-doped carbon nanofibers(CoSe@NCNFs)are successfully by combining the techniques of electrospinning and annealing.Selenium powder are directly dispersed in the polyacrylonitrile/N,N-Dimethylformamide(DMF)solution containing cobalt salt to form the product.The performance of these materials was investigated in Li-ion batteries after the annealing at different temperatures.The Co Se@NC nanofibers annealed at 550℃(CoSe@NC-550)and displayed excellent storage properties,affording a high capacity of 796 m Ah·g~(-1)at a current density of 1 A·g~(-1)for 100 cycles.Moreover,it is confirmed that the pseudocapacitive contribution of CoSe@NC-550 is up to 72.8%at the scan rate of 1 mV/s through the cyclic voltammetry analysis.     

Microporous carbon nanofibers prepared by combining electrospinning and phase separation methods for supercapacitor

Microporous carbon nanofibers(MCNFs) derived from polyacrylonitrile nanofibers were fabricated via electrospinning technology and phase separation in the presence of polyvinylpyrrolidone(PVP).PVP together with a mixed solvent of N,N-Dimethylformamide and dimethyl sulfoxide was used as poreforming agent.The influences of PVP content in casting solution on the structure and electrochemical performance of the MCNFs were also investigated.The highest capacitance of 200 F/g was obtained on a three-electrode system at a scan rate of 0.5 A/g.The good performance was owing to the high specific surface area and the large amount of micro-pores,which enhanced the absorption and the transportation efficiency of electrolyte ion during charge/discharge process.This research indicated that the combination of electrospinning and phase separation technology could be used to fabricate microporous carbon nanofibers as electrode materials for supercapacitors with high specific surface area and outstanding electrochemical performance.     

Polysulfone nanofibers prepared by electrospinning and gas/jet-electrospinning

Polysulfone nanofibers were prepared by electrospinning. The electrospinning equipment was designed in a new way, wherein the spinneret was combined with a gas jet device. The intrinsic viscosity of the used polysulfone was 0.197 dL/g in dimethyl acetamide, which was also the solvent in electrospinning. The gas used in this gas jet/electrostatic spinning was nitrogen. The relationship between the process parameters and the average diameter of polysulfone nanofibers was investigated. The main process parameters studied in this work were the voltage, the flow rate of the spinning fluid, the distance between the spinneret and the nanofiber collector and the temperature in the spinning chamber. The other important factors determining the nanometer diameter were the spinning fluid properties including its viscosity, surface tension and electrical conductivity. The average diameter and the diameter distribution of electrospinning nanofibers were measured experimentally by using scanning electron microscopy. The diameter of polysulfone nanofibers prepared by the gas jet/electrostatic spinning was in the range 50–500 nm. It was found that the diameter of nanofibers mainly depended on high voltage, the gap between the spinneret and the collector and the concentration of polymer solutions. It is concluded that the gas-jet/electrospinning is a better method than the conventional electrospinning, in that it makes the nanofibers finer and more uniform and exhibits higher efficiency in the process of electrospinning. __________ Translated from Acta Polymerica Sinica, 2005, (5) (in Chinese)     

Adsorption of benzene and ethanol on activated carbon nanofibers prepared by electrospinning

Activated carbon nanofibers (ACNFs) were prepared by electrospinning polyacrylonitrile solutions, and subsequent steam activation process. The ACNFs were characterized by scanning electron microscope, X-ray photoelectron spectroscopy and nitrogen adsorption at 77 K. The adsorption equilibrium data for benzene and ethanol were obtained by using static vapor adsorption system. As-prepared ACNFs demonstrate higher adsorption capacities for volatile organic compounds (VOCs) than activated carbon fibers (ACFs) by virtue of smaller diameter and more available adsorption sites on the surface. The adsorption performance of ACNFs increases with the burn-off, as a result of the increased microporosity. In addition, it is noteworthy that surface chemistry has an important effect on the adsorption of polar VOCs. The ACNF with higher oxygen content has a stronger adsorption tendency for ethanol.     

Platelet carbon nanofibers as support of Pt-CoO electrocatalyst for superior hydrogen evolution

Exploration of cost-effective Pt/C catalysts has been a significant issue for electrochemical hydrogen evolution reaction(HER) toward sustainable energy conversion and storage.Herein,we report a fabrication strategy by employing platelet carbon nanofibers(p-CNF) as the support to immobilize Pt-CoO HER electrocatalyst using atomic layer deposition method.The edge-rich p-CNF support is found to act as the anchoring sites of Pt nanoparticles and favorably capture electrons from Pt to yield electron-deficient Pt surfaces for the boosted HER.Additionally,the sequential growth of CoO onto the Pt/p-CNF catalyst elaborately constructs the Pt-CoO interface and facilitates the electron transfer from Pt to CoO,which further enhances the HER activity.These advantages endow the fabricated Pt-CoO/p-CNF catalyst with the superior HER activity,e.g.,a very low overpotential of 26 mV at the current density of 10 mA·cm-2 and a mass activity of 4.42 A·mgPt-1at the overpotential of 30 mV,18.8 times higher than that of the commercial20 wt% Pt/C catalyst.The insights reported here could shed light on for the fabrication of cost-effective Pt-based composite HER catalysts.     

Hydrogen storage capacity of catalytically grown carbon nanofibers

In 1996, R. T. K. Baker, and N. M. Rodriguez claimed to have synthesized a new type of carbon nanofiber material capable of storing large amounts of hydrogen at room temperature and pressures above 100 bar, thus making it a powerful candidate for a very efficient energy storage system in mobile applications. Consequently, many scientists all over the world tried to test and verify these findings, however, with partly inconsistent results. We present here for the first time independent hydrogen storage measurements for several types of nanofibers, both synthesized by our group following precisely the specifications given in the literature as well as original samples supplied by Rodriguez and Baker for this study. The hydrogen storage capacities at room temperature and pressures up to 140 bar were quantified independently by gravimetric and volumetric methods, respectively. No significant hydrogen storage capacity has been detected for all carbon nanofibers investigated.     

电纺法制备中空多管道碳纳米纤维及其氧还原性能

以过渡金属和新型碳材料为代表的非贵金属催化剂具有成本低、稳定性好等优点,被认为是铂基贵金属催化剂的最佳替代品,对于促进燃料电池商业化应用具有重要意义,其中选择一种简单高效的方法制备符合要求的碳载体成为合成该类催化剂的基础.本实验利用静电纺丝技术制备了中空多管道碳纳米纤维,并深入研究了该材料的氧还原性能.结果表明,具有高度开放结构和较大比表面积的中空多管道碳纳米纤维具有较好的催化活性和电流效率,其极限电流密度为4.06mA/cm~2,电子转移数为3.44,是一种优秀的氧还原催化剂.本论文作者探究了中空多管道结构的形成机理,揭示了催化剂的结构和组成与电催化性能之间的构效关系,证明了中空多管道碳纳米纤维可以作为一种优秀的碳载体应用于非贵金属催化剂中.     

Multichannel hollow TiO2 nanofibers fabricated by single-nozzle electrospinning and their application for fast lithium storage

Multichannel hollow TiO₂ nanofibers were synthesized via a facile single-nozzle electrospinning method based on phase-separation mechanism. Compared to normal TiO₂ nanofibers, hollow TiO₂ with higher surface area gave rises to a higher surface contribution and ensured a short diffusion path for ion transport. Thus hollow TiO₂ demonstrated superior cyclic ability and excellent rate capability.     

A simple method for the preparation of activated carbon fibers coated with graphite nanofibers

A simple method is described for the preparation of activated carbon fibers (ACFs) coated with graphite nanofibers (GNFs). Low-pressure-plasma mixed-gas (Ar/O2) treatment of the ACFs led to the growth of GNFs on their surface. The growth was greater at higher power inputs, and from TEM observations the GNFs were seen to be of herringbone type. It was found that the N2 adsorption capacity of the ACFs did not sharply decrease, and that volume resistivity of the ACFs enhanced as a result of this treatment.     

One-dimensional confinement of a nanosized metal organic framework in carbon nanofibers for improved gas adsorption

The loading of a Zn-terephthalate based MOF in the inner cavity as well as on the outer walls of a hollow carbon nanofiber (CNF) creates MOF@CNF hybrids. This hybrid 'MOF@CNF' displayed improved thermal stability as well as gas adsorption compared to the individual counterparts.     

Formation of silica nanofibers with hierarchical structure via electrospinning

Self-standing thiol-functionalized fibrous membrane with bimodal pore structure was successfully fabricated through the combination of electrospinning and surfactant-directing pore formation technique. We also found that the interference of electric field as well as the rapid solvent evaporation during the electrospinning process has a negative effect on the formation of ordered mesoporous structures. As high-performance adsorption-based filtration system, such hierarchically structured membrane is found to efficiently remove Cu (II) ions under high flux.     

Direct synthesis of silver/polymer/carbon nanocables via a simple hydrothermal route

High-yield silver/polymer/carbon nanocables were synthesized via a one-step simple hydrothermal route by using silver chloride and glucose as precursors. High-resolution TEM and element mapping proved that as-prepared nanocables consist of a silver nanowire core, a polymer inner shell, and a graphitic carbon outer shell. A three-step growth mechanism was proposed to explain the growth of such three-layer nanocables, i.e. the formation of silver nanowires, the glycosidation of glucose molecules on silver nanowire surface and the carbonization of the outmost glycosidation layer. We believe that reaction temperature plays the key role in the polymerization of glucose and sequent surface-carbonization.     

Mesoporous carbon nanosheet-assembled flowers towards superior potassium storage

Potassium-ion batteries(PIBs) are attracted tremendous interest for large-scale energy storage systems(ESSs) owing to their economic merits.However,the main challenges of the PIBs are sluggish K-ion diffusion and large volume variations in the potassium repeated intercalation/deintercalation.Herein,mesoporous carbon nanosheet-assembled flowers(abbreviated as F-C) are designed as an original anode for superior-performance PIBs.Specifically,the F-C anode exhibits a high K-storage capacity(e.g.,381 mAh/g at 50 mA/g during the 2~(nd) cycle),excellent rate performance(e.g.,101 mAh/g at 2.0 A/g) and superior long cycle capability.Such excellent K-ion storage property is largely benefited from the large surface area(～141 m~2/g) and reasonable pore volume(0.465 cm~3/g),which not only stimulates rapid Kions diffusion and relieves the huge volume strain,but also exposes extensive active sites for K-ion capacitive storage.     

Alumina nanofibers obtained via electrospinning of pseudo-boehmite sol/PVP solution

Alumina nanofibers were fabricated by calcination of the polyvinylpyrrolidone (PVP)/pseudo-boehmite nanocomposite precursor fibers formed by electrospinning PVP/ethanol solution of dispersed pseudo-boehmite nanoparticles with and without additive of silica. The evolution of the phase, mechanical property and morphological features of the calcined fibers were studied and the effect of adding SiO₂ on the phase transformation of alumina was discussed. Adding SiO₂ can retard the phase transformation of γ-Al₂O₃ to α-Al₂O₃ and therefore inhibit the growth of alumina grains during calcination. Upon calcining the precursor fibers with 4 wt% SiO₂ additive at 1,300 °C, continuous alumina nanofibers with diameter ranging from 300 to 800 nm were obtained. These continuous nanofibers exhibited good flexibility and could be very promising for applications in filtration and catalyst support.     

Cellulose/chitosan hybrid nanofibers from electrospinning of their ester derivatives

A facile approach has been established to generate cellulose/chitosan hybrid nanofibers with full range of compositions by electrospinning of their ester derivatives, cellulose acetate (CA) and dibutyryl chitin (DBC), followed by alkaline hydrolysis to cellulose (Cell) and chitosan (CS). DBC was synthesized by acid-catalyzed acylation of chitin (CHI) with butyric anhydride and the newly formed butyl groups on C3 and C6 were confirmed by FT-IR and ¹HNMR. DBC had robust solubility in acetone, DMAc, DMF, ethanol, and acetic acid, all except ethanol were also solvents for CA, allowing mixing of these ester derivatives. Fiber formation by electrospinning of either DBC or CA alone and together in these common solvents and their mixtures were studied. The 1/1 acetone/acetic acid was found to be the optimal solvent system to generate fibers from either DBC or CA as well as their mixtures at all CA/DBC ratios, resulting in hybrid fibers with diameters ranging from 30 to 350 nm. DBC and CA were well mixed and showed no phase separate in the hybrid fibers. Alkaline hydrolysis (NaOH) of the equal mass CA/DBC nanofibers regenerated Cell and CHI readily via O-deacylation, then proceeded to further deacetylate CHI to CS via N-deacetylation at higher alkaline concentrations and/or temperatures. Under conditions studied, hydrolysis with 5N NaOH at 100 °C for 3 h was optimal to regenerate cellulose/chitosan hybrid nanofibers.