Tubular Carbon Nanofibers Research Articles

Optimization of the TiO2 content and location in core–shell tubular carbon nanofibers to improve the photocatalytic activity under visible light irradiation

Optimization of the TiO2 content and location in core–shell tubular carbon nanofibers to improve the photocatalytic activity under visible light irradiation

Gold recovery through synergetic adsorption and reduction using acid–base additive‐reinforced tubular carbon nanofibers

AbstractIn response to the increasing demand for gold in electronic manufacturing, this study addresses the urgent need for gold recycling from electronic waste (E‐waste) to ensure the environment and energy safety. This study focuses on the preparation of the tubular carbon nanofibers (TCNFs) integrating NH4+ and SO3− groups into TCNF‐SO3−‐NH4+, which exhibited remarkable gold adsorption capacity (2003.25 ± 0.23 mg/g) and selectivity (Kd; 41.7 × 103 mL/g) at lower pH. TCNF‐SO3−‐NH4+ achieved a 99.77% gold adsorption efficiency under lower pH conditions (pH = 1) from E‐waste. The adsorption capacity reached 3.54 ± 0.11 mg/g at an initial concentration of 0.85 mg/L. The results highlight the efficacy of TCNF‐SO3−‐NH4+ for extracting gold and other precious metal ions from E‐waste, presenting a promising solution for clean energy and environmental protection.

Opening tubular structure polyimide/polyvinyl chloride based carbon nanofibers for supercapacitor

Polyimide (PI) and polyvinyl chloride (PVC) blend electrospun fibers are prepared by electrospinning process. PI/PVC electrospun fibers exhibit a certain degree of phase separation due to the incomplete compatibility of PI and PVC in N, N’-dimethylformamide. PI/PVC based carbon nanofibers with opening tubular structure can be obtained via thermally induced phase separation. The effect of precursor composition on the morphology and pore structure of carbon nanofibers is investigated by theoretical calculation and structural analysis. The relationship between pore structure and electrochemical performance of carbon nanofibers is studied significantly. Opening tubular structure carbon nanofibers derived from PI: PVC (mass ratio = 1: 1) electrospun fibers show suitable average pore diameter (5.12 nm), high BET specific surface area (1127.1 m2∙g−1) and large total pore capacity (0.65 cm3∙g−1). And opening tubular structure carbon fibers as electrodes in ionic liquid electrolyte exhibits a wide electrochemical stability window (3.5 V), high energy density (30.1 Wh∙kg−1), good power density (2685.5 W∙kg−1) and low internal resistance (2.1 Ω).

Tubular carbon nanofibers decorated with RuO2 nanorods toward flexible electrochemical capacitors

RuO2 nanorod-decorated tubular carbon nanofibers(CNFs) are carefully fabricated by adjusting the recrystallization temperature for use in high-performance electrochemical capacitors. The tubular structured CNFs/RuO2 electrodes provide a short diffusion path for the ion transport through the inner hollow channel that allowed the maximum utilization of the active sites of the amorphous RuO2 nanomaterials at the electrode/electrolyte interface. The optimized the tubular structured CNFs/RuO2 electrodes exhibit good rate capability with a high surface capacitance, energy density, and good long-term cycling stability of 190 Fg−1, 22 Whkg−1, and 94% after 10,000 cycles, respectively, in an aqueous solution. The asymmetric cell presents a wide and stable operating voltage window, which greatly improves the energy density stored in the asymmetric device. In addition, there is no noticeable difference in the electrochemical properties under bent states, making it a flexible energy storage device for wearable applications. Hence, flexible supercapacitors using CNFs/RuO2 electrodes with the tubular structure show low resistance, high capacitance, good rate retention, and excellent cycle stability, making it a promising material for energy storage applications.

Compression strain-dependent tubular carbon nanofibers/graphene aerogel absorber with ultrabroad absorption band

The compressive strain-dependent microwave dissipation behavior gives aerogel the great possibility of achieving the broad-band absorption. However, there are few investigations that focus on the close association between the compression strain and microwave attenuation performance, and it still remains a vast challenge to construct the elastic microwave absorbers with the good mechanical durability. Herein, by attaching the intertwined tubular carbon nanofibers (TCNFs) to graphene skeleton, lightweight elastic TCNFs/graphene aerogel (TGA) with the anisotropic architecture was formed via chemical cross-linking, freeze-drying and subsequent reduction. When the compression strain is 60% along the vertical direction, the hybrid aerogel is endowed with the satisfactory impedance matching and enhanced conduction loss, originating from the dense cellular configuration. Thus, it harvests the most prominent microwave consumption of a minimum reflection loss (RLmin) value of −46.1 dB and an effective absorption bandwidth (EAB) value of 7.1 GHz. By tuning the compressive strain, an ultrabroad EAB of 11.5 GHz is realized. Besides, the other favorable properties including fatigue resistance, heat insulating and water stability are also acquired. These intriguing features make the hybrid aerogel stand out among numerous absorbers. This study is instructive to develop multifunctional microwave absorbing materials for matching well with the practical environment.

Mo2C nanoparticles coated tubular carbon nanofibers as a highly efficient electrocatalyst for the hydrogen evolution reaction

The development of highly effective and non-precious electrocatalysts for the hydrogen evolution reaction (HER) remains highly desirable. In this work, we report a facile strategy using preoxidized fiber films as a precursor to prepare a flower-like Mo2C-based electrocatalyst for the HER, in which the pyrolysis of a mixture of urea and ammonium molybdate tetrahydrate during thermal treatment realized nitrogen doping. The N–Mo2C/CNFs-900 electrocatalyst exhibits excellent HER activity with a small overpotential of 119 mV at 10 mA cm−2 in an alkaline solution and the Tafel slope was calculated to be 106.9 mV dec−1. N-M-9 demonstrated long term stability over 24 h. With an increase in temperature, MoO2 was gradually transformed into Mo2C and the formation of Mo2C was promoted upon nitrogen doping. This work provides a feasible approach to synthesize high performance HER electrocatalysts for renewable energy applications.

Identification of imprinted sites by fluorescence detection method based on reversible dynamic bond modified template protein

With the development of protein imprinting technique, the certification about the existence of imprinted sites, the arrival of template molecules and target molecules into the same cavity, and the specific separation process based on imprinted sites have seldom been studied so far. To promote the development in the field of protein imprinting, a method for proving the existence of the imprinting sites based on the fluorescence signal changes of the fluorescent materials labeling at the imprinted sites is first proposed in this work. Simultaneously, a novel protein imprinted material with ability of binding signal transduction is developed. The core of the imprinted materials is that bovine serum albumin (BSA) modified by a designed and synthesized functional monomer containing a polymerizable double bond and a cleavable dynamic disulfide bond is selected as a template. And the imprinted polymers supported on the surface of the tubular carbon nanofibers are constructed by thermally initiated polymerization. Fluorescein 4-(N, N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F) is used to label the sulfhydryl groups generated by the cleavage of disulfide bonds at the imprinting sites. The identification of the imprinting sites is achieved by the change in the fluorescent signal generated when BSA is recombined to the imprinting sites. The results of fluorescence detection and adsorption experiments show that the imprinting sites exhibit specific binding and excellent reusability for BSA. In addition, another fluorescein N-(9-acridinyl) maleimide is utilized to label the imprinting sites, which produced a similar fluorescence signal response. Therefore, the experimental results are verified.

High‐Efficiency Microwave Attenuation of Magnetic Carbon Nanoparticle‐Decorated Tubular Carbon Nanofibers Composites at an Ultralow Filling Content

AbstractFaced with the formidable challenge to achieve a powerful absorption and broad bandwidth under a thin response thickness at a low filler content, tailoring the composition and microstructure of the absorbers is generally regarded as a potential method to tackle it. In the study, unprecedented tubular carbon nanofiber/Co/nanoporous carbon (TCNFs/Co/NPC) hybrids with rich holes are obtained by the direct thermal treatment of tubular polymer nanofibers/ZIF‐67 (TPNFs/ZIF‐67) precursor, which is fabricated by controllable anchor of ZIF‐67 nanocrystals on the surface of sulfonated TPNFs (TPNFs‐SO3H). The dielectric parameters of the resultant samples are reasonably monitored by adjustable TPNFs‐SO3H dosage and filling content. Benefiting from the dielectric‐magnetic compositions and unique heterogeneous and porous configurations, the boosted impedance matching and polarization relaxation are given. Hence, under an ultralow filling content of 8 wt%, a minimum reflection loss (RLmin) value of −54.1 dB corresponding to a matching thickness of 2 mm and an effective absorption bandwidth (EAB) of 6.2 GHz at 2.5 mm are exhibited at the TPNFs‐SO3H usage of 100 mg and carbonization temperature of 700 °C, respectively. This work provides an instructive guidance for constructing highly efficient absorbers with strong attenuation and wide frequency range at a low thickness.

Length controllable tubular carbon nanofibers: Surface adjustment and oil adsorption performances

Treatment of oil leakage in an open environment has always been a problem concerned and actively solved in the field of environmental science. Preparation of highly adaptable and efficient adsorption materials has become a research hotspot. In this paper, tubular hypercrosslinked polymer nanofibers are synthesized in the liquid phase by a simple one-step method using a limited self condensation system. The fiber length is controlled effectively by ultrasonic treatment, and the structure-activity relationship between fiber length and oil adsorption properties is established. The effects of surface modifier types, adsorption temperature and time on adsorption capacity are investigated. The O-CTFs-L modified by OTOS has the best adsorption performance and can absorb 13.51−46.73 times of its own weight. After 5 cycles, its adsorption capacities for engine oil 0W-20, soybean oil and diesel oil are still greater than 20 g/g, maintaining more than 73 % of the initial adsorption capacity. O-CTFs-L with a high adsorption capacity and excellent stability is expected to be a potential and advantageous oil adsorption material.

Tailoring carboxyl tubular carbon nanofibers/MnO2 composites for high‐performance lithium‐ion battery anodes

AbstractThree kinds of novel carboxyl modification tubular carbon nanofibers (CMTCFs) and MnO2 composites materials (CMTCFs/MnO2) are prepared by combining hyper‐crosslinking, liquid phase oxidation and hydrothermal technology. The complex morphology and crystal phase of MnO2 in CMTCFs/MnO2 are effectively regulated by adjusting the hydrothermal reaction time. The δ‐MnO2 nanosheet‐wrapped CMTCFs (CMTCFs@MNS) are used as anode and compared with the other two CMTCFs/MnO2. Electrochemical analysis shows that CMTCFs@MNS electrode exhibits a large reversible capacity of 1497.1 mAh g−1 after 300 cycles at 1000 mA g−1 and a long cycling reversible capacity of 400.8 mAh g−1 can be maintained after 1000 cycles at 10 000 mA g−1. CMTCFs@MNS manifests an average reversible capacity of 256.32 mAh g−1 at 10 000 mA g−1 after twelve changes in current density. In addition, the structural superiority of CMTCFs@MNS electrode is clarified by characterizing the microscopic morphology and crystal phase of the electrode after electrochemical performance test.

Facile synthesis of tubular magnetic carbon nanofibers by hypercrosslinked polymer design for microwave adsorption

AbstractIn this study, a simple and efficient method for fabrication of tubular magnetic carbon nanofibers (TMCF) has been developed. Firstly, tubular polymer nanofiber precursors are synthesized by confined self‐condensation method. After carbonization of polymer and in situ transformation of FeCl3 at high temperature, TMCF loaded with Fe nanoparticles is obtained. It has been found that carbonization temperature has significant effects on conductivity, specific surface area, pore volume, defects number in carbon component, and magnetic content of TMCF. The influence of composition, structure, and filler content on microwave absorption properties is revealed. Meanwhile, the microwave absorption mechanism has been analyzed in depth, which benefits from the designed unique structure. The TMCF obtained at 700°C exhibited best performance with the filler content of 15%. The minimum reflection loss is −47.33 dB@2.2 mm, the effective absorption bandwidth is 6.5 GHz (RL < 10 dB), and the matching frequency is 14.1 GHz. The obtained TMCF is lightweight and possess excellent microwave absorption ability, which can be widely used as highly efficient microwave absorber.

Modified Tubular Carbon Nanofibers for Adsorption of Uranium(VI) from Water

Carbon nanomaterials with a hollow tubular nanofiber structure is of great interest for uranium­(VI) adsorption from water. Their unique structure not only exposes a good number of functional groups and high surface area but also shows quick ion transport capacity. However, finding a simple method to prepare a new carbon structure is challenging. Herein, a new tubular hyper-cross-linked polymer is fabricated in a single pot using α,α′-dichloro-p-xylene (DCX) as a monomer. After carbonization, hollow tubular nanofibers (HTnFs) are obtained. Further, HTnFs are modified with carboxylic (COOH) and sulfonic­(SO3H) groups to obtain HTnF-SO3H and HTnF-COOH designed for ultrafast and high uranium­(VI) adsorption from water. From the batch studies, uranium­(VI) adsorption efficiencies of two adsorbents are greater than 90 ± 0.5% under seawater conditions over a short period of 10 min. The accurate data fitting was performed by using different models and the adsorption results are in agreement with the Langmuir model. The adsorption results showing the maximum adsorption capacities of HTnF-COOH and HTnF-SO3H are 1928.59 and 1827.57 mg/g. The easy preparation, highest uranium­(VI) adsorption, and regeneration properties suggest that these adsorbents act as good uranium­(VI) adsorbents from large-scale water.

Fabrication of magnetic tubular fiber with multi-layer heterostructure and its microwave absorbing properties

A new type of microwave absorbing material (TCF@Fe3O4@NCLs) with multi-layer heterostructure is designed and fabricated via a one-step pyrolysis process of the precursor (PF@Fe3O4@PDA). PF@Fe3O4@PDA is prepared by the technology of confined self-polycondensation, solvothermal method coupled with polymerization of dopamine (DA). The as-obtained material has the structure of tubular carbon nanofibers (TCF) embedded with Fe3O4 nanoparticles, dispersed Fe3O4 nanoparticles, and nitrogen-doped carbon layers (NCLs) from inside to outside. Notably, tubular carbon nanofibers provide the major dielectric loss. Fe3O4 nanoparticles significantly improve the microwave absorption ability at low frequencies and provide appropriate magnetic loss. NCLs improve the conductivity and facilitate the generation of multiple polarization effects, resulting in enhanced dielectric loss. The absorption mechanism is further elucidated. Based on the synergistic effect of double dielectric/magnetic loss composite materials, the interface introduced by multi-layer heterostructure, and conductive networks, TCF@Fe3O4@NCLs exhibits excellent reflection loss (RL) of −43.6 dB and effective absorption bandwidth (EBA) of 4.6 GHz (8.2–12.8 GHz) with a loading of 10%. The results demonstrate potentially promising prospects of TCF@Fe3O4@NCLs as new material candidate for microwave absorption.

Core-shell structured Fe/Fe3O4@TCNFs@TiO2 magnetic hybrid nanofibers: Preparation and electromagnetic parameters regulation for enhanced microwave absorption

In this paper, a three-step method has been applied for preparation of Fe/Fe3O4@TCNFs@TiO2 magnetic hybrid nanofibers (MHNFs) with three-layer core-shell structure. Firstly, tubular polymer nanofiber precursors with FeCl3 embedded in axis (TPNFPs) are synthesized by a confined self-condensation system developed earlier. After high-temperature conversion, tubular magnetic carbon nanofibers loaded with Fe nanoparticles inside (Fe@TCNFs) are obtained. Finally, TiO2 shell formation procedure is carried out by the hydrolysis of tetrabutyl titanate, and MHNFs with different TiO2 loadings are successfully fabricated. This material possesses both magnetic and dielectric loss abilities that shows excellent microwave absorbing performance. Under filler content of 15 wt%, the minimum reflection loss reaches −44.8 dB@13.9 GHz, and the absorbing layer thickness is only 1.6 mm. In addition, the electromagnetic parameters of MHNFs can be regulated and optimized by adjusting TiO2 loading. It brings better impedance matching property and improves microwave absorbing performance. Meanwhile, the composition, structure and electromagnetic parameters of MHNFs are systematically analyzed. The microwave attenuation mechanism is revealed. This study has guiding significance for the performance optimization of existing microwave absorbers.

Preparation of CTCNFs/Co9S8 hybrid nanofibers with enhanced microwave absorption performance

A three-step synthesis strategy has been applied to the preparation of Co9S8-loaded tubular carbon nanofibers (CTCNFs/Co9S8 hybrid nanofibers) with excellent microwave absorbing ability. Firstly, tubular polymer nanofibers (TPNFs) are synthesized using the confined self-condensation method that we developed. Afterwards, TPNFs are converted into surface carboxylated tubular carbon nanofibers (CTCNFs) by carbonization and subsequent acidification processes. Finally, a hydrothermal method is used for the controllable growth of Co9S8 nanoparticles on CTCNFs, and a series of CTCNFs/Co9S8 hybrid nanofibers with different Co9S8 loading are obtained. The prepared CTCNFs/Co9S8 hybrid nanofibers possess abundant effective interface and defect dipoles, which will lead to stronger polarization. Using the strategy of enhancing dielectric loss, the microwave dissipation ability of CTCNFs/Co9S8 hybrid nanofibers has been significantly improved, showing an excellent low-frequency absorbing performance with a minimum reflection loss of −46.81 dB@5.3 GHz. In addition, the composition, structure and properties of nanofibers have been systematically characterized. The Co9S8 loading on CTCNFs and the filler content of CTCNFs/Co9S8 hybrid nanofibers in matrix are studied and optimized. The microwave attenuation mechanism is also explained.

Self-Driven BSA Surface Imprinted Magnetic Tubular Carbon Nanofibers: Fabrication and Adsorption Performance

The development of materials with high adsorption capacity and selectivity, simple operation, and short adsorption equilibrium time are still a focus in the domain of imprinting techniques. Based o...

Magnetic tubular carbon nanofibers as efficient Cu(II) ion adsorbent from wastewater

Abstract Novel magnetic tubular carbon nanofibers (MTCFs) were prepared from hypercrosslinked α, ά-dichloro-p-xylene as a green adsorbent for efficient Cu(II) ion removal from the wastewater. The new route involving the following steps, such as dual oil phase polymerization, carboxyl functionalization and loading of magnetic nanoparticles (Fe3O4) was developed. The surface area, saturation magnetization, inner and outer diameters of MTCFs are 280.94 m2/g, 10.65 emu/g, 25 nm and 110 nm. The adsorption properties were studied by batch methods. The highest removal efficiency for Cu(II) ion was achieved 99.9 ± 0.1% in a short contact time 10 min and a small amount of MTCFs dosage 0.5 g/L with pH = 6. From kinetic studies, the Pseudo first order kinetic model was best fitted with experimental data than the Pseudo second order. From isothermal studies, the Langmuir model was best fixed with the highest R2 in contrast to the Freundlich isotherm model. The highest adsorption for Cu(II) ion 375.93 mg/g was achieved from the Langmuir isotherm. The parameters determined from thermodynamics ΔGᵒ, ΔHᵒ, ΔSᵒ confirmed Cu(II) ion adsorption was spontaneous, thermodynamically it was endothermic and random adsorption process. Regeneration and reuse of MTCFs up to six cycles with the same contact for all adsorption cycles.

Magnetic tubular carbon nanofibers as anode electrodes for high‐performance lithium‐ion batteries

Magnetic tubular carbon nanofibers as anode electrodes for high‐performance lithium‐ion batteries

(Amazon Catalyst at ECS Grant Winner) Carbon Catalysts for Cost-Efficient Hydrogen Production in PEM Electrolyzers

Exposure of single-walled carbon nanotubes (CNTs), as well as other lower cost layered graphitic carbons (LGCs), to acidic intercalants, in combination with low voltage electrochemical cycling, induces in these materials hydrogen evolution activity that initiates at near zero overpotential and is on par with that of platinum catalysts.1 These results encouraged the further development and testing of the CNT catalyst in a PEM water splitting electrolyzer prototype. Once activated, the CNT cathode demonstrated 1 A/cm2 of HER current at 1.64 V, comparable to a similarly tested commercial Pt-loaded cathode. While carbon nanotubes are not intrinsically scarce, the single wall nanotubes used in these electrode tests remain relatively expensive. Commercial significance would benefit from a demonstration of comparable performance from activated lower cost layered graphitic carbons in a PEM electrolyzer prototype. The following LGC materials, having a combination of high electrical conductivity, large pore volumes, and high specific surface areas, were tested in terms of their ability to achieve low HER overpotential during the activation process: microcrystalline graphitic particles, Vulcan XC-72 carbon, highly graphitized stacked-cup tubular carbon nanofibers (CNFs), and carbon needle felt. CNF electrodes demonstrated slightly higher mass basis activity than that of the other tested LGCs in acid electrolyte in a standard three-terminal electrochemical cell. Here we report excellent performance from activated CNF cathodes, prepared by a scalable spray-coating method, in our PEM electrolyzer prototype (IrRuOx as anode catalyst). As anticipated, a control MEA, based on the non-activated CNF cathode and tested in PEM electrolyzer under identical conditions, showed poor performance, indicating a low electrocatalytic HER activity of the electrode. The activated CNF cathode-based PEM electrolyzer achieved 1 A/cm2 at 1.78 V, while a control commercial MEA with Pt-loaded cathode/IrRuOx anode (a high Pt catalyst loading of 3 mg/cm2 cathode, Fuel Cells Etc) tested in the same PEM electrolyzer cell demonstrated 1 A/cm2 at 1.7 V. Acknowledgements. This work is supported by Amazon through ECS Amazon Catalyst Program.

Tubular carbon nanofibers: Synthesis, characterization and applications in microwave absorption

In this paper, hypercrosslinked tubular polymer nanofibers (TPNF) are synthesized by Friedel-Crafts alkylation in a confined self-condensation system. Using TPNF as precursor, tubular carbon nanofibers (TCNF) with two-level pore structure are prepared by carbonization. The high specific surface area, reasonable pore structure, light weight, large aspect ratio and other significant advantages make TCNF exhibit excellent microwave absorption performance. The inner diameter of TCNF ranges from 25 to 40 nm and the wall thickness is about 30 nm. The effects of carbonization temperature on morphology, graphitization degree and pore properties are investigated. Meanwhile, the microwave absorption performance of the products at different carbonization temperature has been evaluated. The optimum carbonization temperature and absorber loading are confirmed to be 700 °C and 10%, respectively. Under this condition, the minimum reflection loss is −61.5 dB, and the effective absorption bandwidth can reach 4.25 GHz. The microwave absorbing mechanism includes moderate conductive loss, multiple reflection and scattering, interfacial polarization, Debye relaxation and good impedance matching. The obtained TCNF enriches the types and synthesis methods of carbon materials. As a highly efficient lightweight microwave absorber, TCNF possesses potential value in the synthesis and application of new composite microwave absorbing materials.