Prepare Carbon Nanofibers Research Articles

Effect of adding lignin on preparation and properties of pitch/PAN‐derived electrospun nanofibers inducing cross‐linking structure

AbstractIn this work, the content of lignin, pitch, and PAN as well as the preparation process would be systematically controlled in order to prepare carbon nanofibers (CNFs) with cross‐linked structure, high specific surface area, and good flexibility. The evolution of nanofibers with different lignin contents during stabilization and carbonization were explored, and the properties of the resultant CNFs as supercapacitor self‐supported electrodes were compared. The results indicated that with the increase of lignin content, not only cross‐linked structures were introduced in CNFs, but also the flexibility were obviously improved, accomplishing for supercapacitor self‐supported electrodes. Moreover, CNFs with different content of lignin varied in fiber morphology and microstructure, harvesting developed porous structure in CNFs. PPL3‐CNF prepared with adding lignin at a mass ratio of 3/7 into a concentration of 10 wt.% pitch/PAN solution presented the highest specific surface area of 949 m2 g−1, exhibiting an excellent specific capacitance of 190.7 F g−1 at 0.2 A g−1.

Rheological properties and dry-cracking resistance of cementitious materials modified by CNFs doping

With the continuous development of building material science, modified cementitious materials have become a popular research direction. Carbon nanofibers, because of their unique properties, their application potential is shown in the construction field. To raise the rheological properties and dry-cracking resistance of cementitious materials, this study used mechanical shear method to prepare carbon nanofibers with different dosages. Subsequently, the rheological properties, compressive properties and dry cracking resistance of cementitious materials with different dosages were tested to obtain the optimal values of carbon nanofibrillated cellulose dosage. The study compared the application effect of the modified cementitious materials with that of the conventional cementitious materials. The experiment outcomes indicated that the highest shear stress of 118.7 Pa was observed in the cementitious material with 0.2 % carbon nanofibrillated cellulose dosage at 0.5 water-to-cement ratio, and the most significant reduction of self-shrinkage of 0.1 % carbon nanofibrillated cellulose dosage was observed in the cementitious material with a self-shrinkage reduction of 0.76. In addition, carbon nanofibrillated cellulose-based cementitious materials also showed good practical application effects. The above results indicate that carbon nanofibrillated cellulose can provide better performance for cementitious materials, which provides new possibilities for the development of high-performance cementitious materials.

Understanding the behaviors of ZIF-67 reinforced electrospun carbon nanofibers in the preparation and stabilization

MOFs-reinforced electrospun carbon nanofibers offer a wide range of applications in the field of energy storage. In this study, ZIF-67 nanoparticles were produced and combined with polyacrylonitrile for electrospinning before being stabilized and carbonized to form a carbon nanofiber. BET, FT-IR, EA, DSC, and other techniques were used to investigate the stabilizing behaviors of PAN electrospun fiber with varying ZIF-67 concentrations at different temperatures. Under the same stabilizing settings, it was discovered that PAN electrospun fiber containing ZIF-67 nanoparticles could absorb more oxygen, promoting a higher degree of cyclization and crosslinking. Therefore, it was preferred to prepare carbon nanofibers at a lower stabilization temperature. Importantly, the degree of stability and disorder of the PAN/ZIF-67 stabilized fiber has been described by the FT-IR and the Raman spectra. This research deepens understanding about the formation of MOF-reinforced carbon nanofibers and expands our knowledge of the stability of PAN/MOF hybrid fibers.

Sustainable and Green Synthesis of Carbon Nanofibers from Date Palm Residues and Their Adsorption Efficiency for Eosin Dye

This work investigates the prospective usage of dried date palm residues for eosin Y and eosin B (ES-Y and ES-B) dye removal from an aqueous solution. A green synthesis route is utilized to prepare carbon nanofibers (CNFs) from date palm residues. We study the characteristics of carbon nanomaterials based on their composition and morphology. The characterization includes different types of instruments such as a Fourier-Transform Infrared Spectroscopy (FTIR), Brunauer Emmett Teller (BET), and Scanning Electron Microscopy (SEM). Batch mode experimentations are conducted and studied utilizing various significant factors such as the dose of the adsorbent, solution pH, contact time, and the initial quantity of eosin molecules as a pollutant. The dye adsorption capability improves with an increasing adsorbent dose of up to 40 mg of CNFs. The adsorption of dyes onto CNFs achieves equilibrium in around 60 h, whereas the optimal starting dye concentration in this study is 50 ppm. Further, to study the under-investigated toxic molecules’ adsorption process mechanism on the nanomaterials’ active sites, we introduce kinetic models involving pseudo-first-order, pseudo-second-order, and models based on intra-particle diffusion. Langmuir and Freundlich’s isotherms are considered to study the equilibrium isotherms, and the Langmuir isotherm model deals considerably with the attained experimentation results.

Carbon nanofibers with gas selective layer containing rich and accessible ultramicropores for methane/nitrogen separation

The adsorption separation and purification of coalbed methane (CH4) has attracted global interest as an important technique for the utilization of unconventional natural gas. The success for this method relies on the development of adsorbent materials that can selectively enrich CH4. Toward this goal, we report a facile in-situ growth method to prepare carbon nanofibers with ultramicroporous gas selective layer as adsorbent for CH4/N2 separation. The thickness of gas selective layer can be precisely tuned from 90 nm to 525 nm. The optimal carbon nanofibers exhibited a high CH4/N2 selectivity of 6.8 with the CH4 uptake reaching 0.97 mmol g−1 as well as two orders of magnitude faster CH4 diffusion kinetics than the commercial activated carbon adsorbent. The high accessibility to the adsorption sites and short diffusion path of the nanofibers facilitate the rapid mass transfer and intensify the dynamic CH4/N2 separation. Pressure swing adsorption simulations indicated the recovery and productivity over the carbon nanofibers with 90 nm-thick gas selective layer increased by 40 % and 20 %, respectively, as compared to the 525 nm-thick counterparts. This work offers a new insight for designing high-performance CH4/N2 adsorbents through suitable combination between rich ultramicropores and short diffusion path.

A Novel Triple Crosslinking Strategy on Carbon Nanofiber Membranes as Flexible Electrodes for Lithium-Ion Batteries.

In order to solve the problem of low electrical conductivity of carbon nanofiber membranes, a novel triple crosslinking strategy, including pre-rolling, solvent and chemical imidization crosslinking, was proposed to prepare carbon nanofiber membranes with a chemical crosslinking structure (CNMs-CC) derived from electrospinning polyimide nanofiber membranes. The physical-chemical characteristics of CNMs-CC as freestanding anodes for lithium-ion batteries were investigated in detail, along with carbon nanofiber membranes without a crosslinking structure (CNMs) and carbon nanofiber membranes with a physical crosslinking structure (CNMs-PC) as references. Further investigation demonstrates that CNMs-CC exhibits excellent rate performance and long cycle stability, compared with CNMs and CNMs-PC. At 50 mA g−1, CNMs-CC delivers a reversible specific capacity of 495 mAh g−1. In particular, the specific capacity of CNMs-CC is still as high as 290.87 mAh g−1 and maintains 201.38 mAh g−1 after 1000 cycles at a high current density of 1 A g−1. The excellent electrochemical performance of the CNMs-CC is attributed to the unique crosslinking structure derived from the novel triple crosslinking strategy, which imparts fast electron transfer and ion diffusion kinetics, as well as a stable structure that withstands repeated impacts of ions during charging and discharging process. Therefore, CNMs-CC shows great potential to be the freestanding electrodes applied in the field of flexible lithium-ion batteries and supercapacitors owing to the optimized structure strategy and improved properties.

MoS2-Decorated Graphene@porous Carbon Nanofiber Anodes via Centrifugal Spinning.

Sodium-ion batteries (SIBs) are promising alternatives to lithium-ion batteries as green energy storage devices because of their similar working principles and the abundance of low-cost sodium resources. Nanostructured carbon materials are attracting great interest as high-performance anodes for SIBs. Herein, a simple and fast technique to prepare carbon nanofibers (CNFs) is presented, and the effects of carbonization conditions on the morphology and electrochemical properties of CNF anodes in Li- and Na-ion batteries are investigated. Porous CNFs containing graphene were fabricated via centrifugal spinning, and MoS2 were decorated on graphene-included porous CNFs via hydrothermal synthesis. The effect of MoS2 on the morphology and the electrode performance was examined in detail. The results showed that the combination of centrifugal spinning, hydrothermal synthesis, and heat treatment is an efficient way to fabricate high-performance electrodes for rechargeable batteries. Furthermore, CNFs fabricated at a carbonization temperature of 800 °C delivered the highest capacity, and the addition of MoS2 improved the reversible capacity up to 860 mAh/g and 455 mAh/g for Li- and Na-ion batteries, respectively. A specific capacity of over 380 mAh/g was observed even at a high current density of 1 A/g. Centrifugal spinning and hydrothermal synthesis allowed for the fabrication of high-performance electrodes for sodium ion batteries.

One-step solvothermal synthesis of wood flour carbon fiber/BiOBr composites for photocatalytic activation of peroxymonosulfate towards sulfadiazine degradation: Mechanisms comparison between photo, chemical and photo-chemical oxidation processes

Facile preparation of novel catalysts which can effectively activate peroxymonosulfate (PMS) under visible light is of great significance for rapid degradation of refractory organic chemicals in water. Herein, one-step solvothermal process was introduced to prepare carbon nanofiber incorporated bismuth oxybromide (BiOBr/SCF) composites, in which commercial wood flour was in-situ converted to carbon fiber with graphitic structure and incorporated with BiOBr via the process. At the existence of PMS, the prepared composites exhibited prominent visible-light photocatalytic degradation capability towards sulfadiazine (SDZ) with satisfying adaptability and recyclability. Specifically, the apparent pseudo-first order kinetic constant of BiOBr/SCF-180/PMS/visible light system (0.0724 min−1) exceeded those of both BiOBr/SCF-180/PMS (0.0462 min−1) and BiOBr/SCF-180/visible light (0.0111 min−1) systems. An integrated mechanism in the BiOBr/SCF/PMS/visible light system was elucidated through comparing the mechanisms amongst photo-oxidation, chemical oxidation and photo-chemical oxidation systems, in which photo-induced electron and hole, Bi3+/Bi5+ redox couple, graphitic structure and oxygen functional groups in the SCF all participated in the generation and conversion of the active species. The possible SDZ degradation pathway was also proposed. This work demonstrates a novel strategy to prepare high-efficient catalysts in the field of wastewater treatment.

Effects of Prepared Carbon Nanofibers on Properties of Emulsified Asphalt

Abstract To prepare new carbon nanofiber (CNF) for improving properties of emulsified asphalt, CNF-I were first prepared by chemical vapor deposition method. Then the microstructure morphology, specific surface area, pore size distribution, and crystal structure of prepared CNF-I were characterized and compared with those of commercial CNF-II using a field emission scanning electron microscope, automatic specific surface area and aperture distribution instrument, and X-ray diffractometer, respectively. Also, CNF-I and styrene-butadiene-styrene (SBS) latex were utilized to prepare composite modified emulsified asphalt (CS/MEA) and its evaporated residue (ER) samples. Then basic properties of CS/MEA were tested, the dispersity of CNF-I and SBS modifier particles in ER were observed using a confocal laser scanning microscope, and the thermal properties of ER were discussed by using a differential scanning calorimeter. Test results indicate that prepared CNF-I shows cleaner microscopic surface morphology and lower agglomeration degree. The purity and graphitization degree of CNF-I are higher than those of CNF-II, so that the atomic interlaminar force of CNF-I is stronger and the crystal structure is tighter. These improve the surface activity and bonding performance of CNF-I with asphalt. Therefore, CNF-I is selected as a modifier to reinforce emulsified asphalt. Next, basic properties of CS/MEA meet relevant technical requirements. The addition of CNF-I decreases the penetration but increases the softening point of ER. The ductility is first increased and then decreased and reaches the maximum value at the CNF-I content of 0.05 weight percent (wt%). Further, CNF-I forms a spatial network structure in ER and improves the swelling degree of SBS, which causes the phase structure of ER to become more stable. However, when the CNF-I content is higher than 0.05 wt %, the agglomeration occurs to decrease properties of emulsified asphalt. It is found that prepared CNF-I improves properties of emulsified asphalt at the CNF-I content of 0.05 wt %, which is proposed to develop new CS/MEA.

Thermal Engineering of NiCo‐Codoped Carbon Nanofibers toward Enhanced Oxygen Electrocatalysis for Zn–Air Batteries

Electrospinning is an efficient and facile method to prepare carbon nanofibers (CFs) embedded with a NiCo alloy as efficient oxygen electrocatalysts for Zn–air batteries. The subsequent pyrolysis of electrospun‐woven is significant to the crystallization degree of CFs and NiCo alloy. Herein, the effect of the crystallization degree of the alloy and carbon on the oxygen electrocatalytic activity is explored through controlled thermal engineering (the annealing temperature). As the temperature increases, the degree of crystallization and agglomeration of nanoparticles increases simultaneously, accompanied by the increase of the graphitization degree of CFs. Among all the samples, NiCo/CF‐800 exhibits the best oxygen bifunctional catalytic activity (ΔE = 0.73 V). A Zn–air battery based on the NiCo/CF‐800 catalyst exhibits a high peak power density (168.6 mW cm−2), high specific capacity (802.6 mA h gZn−1), and excellent charge/discharge cycling stability. This work provides new insight into catalysts through thermal engineering, promoting the practical application of electrospinning as a large‐scale production method.

Processing, microstructure and electrochemical properties of reduced graphene oxide reinforced carbon nanofiber formed by gyration

In this paper, graphene oxide (GO) were added into polyacrylonitrile to prepare carbon nanofiber by using gyration and subsequent carbonization process as to improve their electrochemical properties. The microstructure and electrochemical properties of prepared carbon nanofiber samples were investigated by using scanning electron microscopy and electrochemical workstation, respectively. The effects of the addition amount of graphene oxide and carbonation temperature on the microstructure and electrochemical properties of composite carbon nanofibers were studied.

Designing g‐C3N4/N‐Rich Carbon Fiber Composites for High‐Performance Potassium‐Ion Hybrid Capacitors

Potassium‐based energy storage devices (PEDS) are considered as hopeful candidates for energy storage applications because of the abundant potassium resources in nature and high mobility in the electrolyte. although carbon materials show great potential for potassium‐ion storage, poor rate performance, and unsatisfactory cycle lifespan in existing carbon‐based PIBs anode, it also cannot match the dynamics and stability of the capacitor cathode. Nitrogen doping has been proven to be a effective modification strategy to improve the electrochemical performance of carbon materials. Hence, we prepare carbon nanofibers and g‐C3N4 composites with high nitrogen contents (19.78 at%); moreover, the sum of pyrrolic N and pyridinic N is up to 59.51%. It achieves high discharge capacity (391 mAh g−1 at 0.05 A g−1), rate capacity (141 mAh g−1 at 2 A g−1), and long cycling performance (201 mAh g−1 at 1 A g−1 over 3000 cycles) when as an anode for PIBs. Furthermore, it can deliver promising discharge capacity of 132 mAh g−1 at 0 °C. Moreover, as battery anode for potassium‐ion hybrid capacitors (PIHC) device with an active carbon cathode, it delivers energy/power density (62 and 2102 W kg−1) as well as high reversible capacity (106 mAh g−1 at 1 A g−1).

Rational Fabrication and Improved Lithium Ion Battery Performances of Carbon Nanofibers Incorporated with α-Fe2O3 Hollow Nanoballs

The present results contribute a facile route to prepare carbon nanofibers hybrided with hollow metal oxide nanoparticles under the assistance of Kirkendall effect. α‒Fe2O3 hollow nanoball incorporated carbon nanofibers (denoted as FOCNFs) are rationally fabricated by using electrospun composite carbon nanofibers (CNFs) as the precursors. The hollow nanoparticles are 69.8 nm in the average size with the shell thickness of 14 nm. The composite nanofibers are hierarchically porous. The mesopores are in the range of 2 ‒ 10 nm and center at 3.7 nm. The micropores center at 0.5 nm with the micropore volume of 0.02 cm3·g−1. Time dependant morphology evolutions confirm that the formation of α‒Fe2O3 hollow nanoballs is promoted by the nanoscale Kirkendall effect due to the migration difference between oxygen molecules and Fe3+ cations in the solid. This route is also successfully extended to fabricate hollow Co3O4 and NiO nanoparticles incorporated carbon nanofibers. FOCNFs exhibit improved lithium ion battery performances with enhanced capacity, rate capability and long-term cycling stability. The optimized sample of FOCNFs‒30 delivers a high initial capacitance of 1903.8 mAh·g-1 at 100 mA·g-1. A reversible capacity of 601.2 mAh·g-1 sustains at 0.1 C after 300 charge-discharge cycles. The improved electrochemical performances of FOCNFs stem from coupling the characteristics of α-Fe2O3 nanoballs and porous nanofibrous carbon matrix.

Investigation of Structure and Chemical Composition of Carbon Nanofibers Developed From Renewable Precursor

In this study, lignin-based carbon nanofibers were prepared by electrospinning, followed by carbonization at four different temperatures (800, 1000, 1200, and 1400 °C). The surface and bulk elemental compositions were analyzed by energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy, respectively. In addition, the structure of the prepared carbon nanofibers was characterized by scanning electron microscopy, transmission electron microscopy, focused ion beam microscopy, and Raman spectroscopy. Results showed that all carbon nanofibers, irrespective of the carbonization temperature, had homogeneous structures. They were dense and no phase separation was observed. Moreover, the nanofibers carbonized at 800 °C or 1000 °C predominately contained amorphous carbon and some non-carbon elements. When the carbonization was performed at a higher temperature (1200 °C or 1400 °C), non-carbon elements were effectively removed and nanocrystalline graphite was formed, indicating that high temperature carbonization facilitated the formation of ordered carbon structures.

Electro-catalytic Activity of Carbon Nanofibers Supported Palladium Nanoparticles for Direct Alcohol Fuel Cells in Alkaline Medium

Carbon nanofibers (CNFs) were successfully prepared employing a chemical vapor deposition method using chicken oil as a starting material. CNFs acquired from waste chicken fat represent a fascinating alternative to produce low-cost/cheap fuel cell electro-catalysts. The Pd/CNF electro-catalyst was synthesized using carbon nanofibers as a support material without adjusting the pH of the solution. The synthesized nanomaterials were studied using Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Transmission electron microscopy (TEM), X-ray diffractometry (XRD), and X-ray photoelectron spectroscopy (XPS). The FTIR outcomes confirmed that the prepared carbon nanofibers are functionalized with carboxylic acid functional groups which enhance the dispersion of Pd nanoparticles. The Raman spectrum revealed that the synthesized CNFs contain two peaks D and G bands, which correspond to a disordered carbon peak (D) and graphite peak (G). TEM pictures confirmed that the synthesized nanomaterials were of the nanoscale and not uniformed in size. XRD peaks confirmed that the carbon nanofibers were amorphous and Pd (111) was observed in the Pd/CNF electro-catalyst. XPS results showed the composition of the prepared samples and the oxidation states of Pd in Pd/CNF electro-catalyst. The Pd/CNF electro-catalyst prepared by CVD method exhibits superior performance towards the electro-oxidation of ethanol and methanol as compared to the commercial palladium electro-catalyst.

Preparation of carbon nanofiber with multilevel gradient porous structure for supercapacitor and CO2 adsorption

In this work, we demonstrate a simple method to prepare carbon nanofiber (CNF) with multilevel gradient porous structure derived from polyvinylidene fluoride (PVDF)- polyvinyl pyrrolidone (PVP) /PVP core-shell nanofiber. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have confirmed that the as-prepared CNF contains a hollow channel embraced by mesoporous and microporous structures. Its specific surface area reaches to 1084 m2/g with the mesoporous volume contribution of 59%. The as-prepared porous CNF shows a high capacitance of 331 F/g at 1 A/g and 99.6% capacitance retention after 10,000 cycles at 5 A/g, which is better than the corresponding CNF with irregularly arranged hierarchical pores. The all-solid-state symmetric supercapacitor assembled using the as-prepared porous CNF as electrodes exhibits an excellent high specific capacitance of 147.4F/g at 1 A/g with a high energy density of 13.1 W h/kg. The capacitance retention still maintains at 89.2% after 2000 cycles at a current density of 5 A/g. Meanwhile, the as-prepared porous CNF also shows a high CO2 adsorption uptake, 5.08 mmol/g at 0 °C and 1 bar. The possible reason and mechanism have been discussed.

Coal Liquefaction Residues Based Carbon Nanofibers Film Prepared by Electrospinning: An Effective Approach to Coal Waste Management

As a major byproduct of direct coal liquefaction, coal liquefaction residue (CLR) waste is environmentally harmful but also valuable. Considering environmental and economic efficiency, exploiting these wastes as electrodes for new generation energy storage devices will increase the economic value and decrease environmental pollution synchronously. In this regard, CLRs are used to prepare carbon nanofibers film for supercapacitors via electrospinning followed by HNO3 preoxidization, air stabilization, and carbonization processes for the first time. The influences of HNO3 preoxidization over the formation of fiber morphology, textural structure, surface chemistry, and electrochemical performance are investigated. Our work demonstrates that HNO3 preoxidization can enhance the content of the heteroatom of the as-spun nanofibers and promote the polymerization of the asphaltene (CLRA) molecular during air stabilization, leading to the changes of the thermal behaviors and thus avoiding the fibers melting success...

Morphological study of stabilization and carbonization of polyacrylonitrile/TiO2 nanofiber mats

Polyacrylonitrile belongs to the most often used precursors for carbon fibers. Using electrospinning, polyacrylonitrile nanofiber mats can be prepared and afterwards stabilized and carbonized to prepare carbon nanofiber mats which, by adding other materials, will be useful for several applications. One of these materials is TiO2, which has photocatalytic properties and can thus be used as a photocatalyst for photodegradation of dyes. Here, we report on a detailed study of electrospinning, stabilization, and carbonization of electrospun polyacrylonitrile/TiO2 mats with varying TiO2 content. Depending on the amount of TiO2 in the nanofibers, the fiber morphology changes strongly, indicating an upper limit for the preparation of carbon/TiO2 nanofibers with smooth surface, but offering an even increased inner surface of the rougher carbon/TiO2 nanofibers with increased TiO2 content due to better maintenance of the fibrous structure during stabilization.

High Performance Supercapacitor Electrode Materials from Electrospun Carbon Nanofibers in Situ Activated by High Decomposition Temperature Polymer

Most previous works on in situ activation of electrospun carbon nanofibers have usually used a sacrificing polymer with a low decomposition temperature (e.g., less than 300 °C) as an activation agent, which leads to limited mesoporous structure and surface area in the carbon nanofibers. In this study, we have prepared carbon nanofibers by carbonization of electrospun polyacrylonitrile (PAN) in the presence of a high decomposition temperature polymer, polysulfone (PSF), which is homogeneously blended with PAN. The use of PSF as in situ activation agent largely increased mesopore content, specific surface area, graphitization degree, interfiber connection, and conductivity in the carbon nanofibers. The PAN/PSF ratio showed an effect on these properties, and 20% PSF within the precursor nanofibers (based on the polymer weight) had the best results. When using the PAN/PSF derived carbon nanofibers as an electrode material, the prepared supercapacitor showed a specific capacitance as high as 289 F/g at the sca...

Binder-Free N- and O-Rich Carbon Nanofiber Anodes for Long Cycle Life K-Ion Batteries.

Carbon nanofibers produced by electrospinning of polyacrylonitrile polymer and subsequent carbonization were tested as freestanding potassium-ion anodes. The effect of oxygen functionalization on K-ion carbon anode performance was tested for the first time via plasma oxidation of prepared carbon nanofibers. The produced materials exhibited exceptional cycling stability through the amorphous carbon structuring and one-dimensional architecture accommodating significant material expansion upon K+ intercalation, resulting in a stable capacity of 170 mAh g-1 after 1900 cycles at 1C rate for N-rich carbon nanofibers. Excellent rate performance of 110 mAh g-1 at 10C rate, as compared to 230 mAh g-1 at C/10 rate, resulted from the K-ion surface storage mechanism and the increased K+ solid diffusion coefficient in carbon nanofibers as compared to graphite. Plasma oxidation treatment augmented surface storage of K+ by oxygen functionalities but increased material charge transfer resistance as compared to N-rich carbon fibers. Ex situ characterization revealed that the one-dimensional structure was maintained throughout cycling, despite the increase in graphitic interlattice spacing from 0.37 to 0.46 nm. The carbon nanofibers demonstrate great potential as an anode material for potassium-ion batteries with superior cycling stability and rate capability over previously reported carbon materials.