Polyacrylonitrile-based Carbon Nanofibers Research Articles

Preparation of Phosphorus/Hollow Silica Microsphere Modified Polyacrylonitrile-Based Carbon Fiber Composites and Their Thermal Insulation and Flame Retardant Properties

Since thermal insulation materials with a single function cannot satisfy the increasing requirements for complex usage, the combination of thermal insulation with flame retardancy is desirable in multiple applications. Herein, phosphorous-containing flame retardant modifier (5.0 wt.%, 9.0 wt.%, and 13.0 wt.%) and hollow silica microsphere (130 nm of diameter) were composited with polyacrylonitrile-based carbon nanofibers via electrospinning technique. Electrospun phosphorous/silica/carbon nanofibers (P/HSM/CF) exhibited a uniform and clear fibrous structure (508, 170, and 1550 nm of average fiber diameter) with modified uniform and complete spherical silica. Reduced thermal conductivity (39.9–41.2 mW/m/K) and enhanced limiting oxygen index (29.5–33.5%) were achieved, enabling fire protection grade of fiber membrane from UL-94 V-1 grade to UL-94 V-0 grade efficiently. Moreover, favorable tensile strength (8.64–9.27 MPa) and elongation at break (43.28–48.54%) were obtained, presenting expected applications in structural components. The findings of this work provided a valuable reference for the fabrication of carbon nanofiber-based thermal insulation materials with excellent flame retardant and mechanical properties.

Polyacrylonitrile-based carbon nanofiber electrode fabricated via electrospun for supercapacitor application

The versatile properties of electrospun carbon nanofibers gaining attention for electrode materials for supercapacitors. The heat treatment process of stabilization played an important role before the carbonization process in electrode fabrication. In the present study, electrospun stabilized polyacrylonitrile nanofiber (St PAN) and carbonized Polyacrylonitrile nanofiber (CNF) at minimum temperature were used as active mass for supercapacitor electrodes. Stabilized CNF nanofiber sample showed a reduction in nanofiber diameter with increased carbon percentage. XRD results showed increased crystallinity in the CNF sample as compared with the Stabilized PAN sample. Electrochemical characterization was performed to measure specific capacitance and to analyze the charge storage mechanism. The proportion of capacitive and diffusion-controlled contributions to energy storage was estimated using Dunn’s model. The results obtained demonstrated that, in comparison to the St PAN electrode, the CNF electrode exhibited a greater capacitive-controlled contribution. The CNF sample has shown an increased capacitive contribution of 82.3% as compared with the St PAN sample. This work provides a method for making electrospun carbon nanofiber-based electrodes as well as a methodical methodology for examining the charge storage process.

Breakthrough analysis of the CO2/CH4 separation on electrospun carbon nanofibers

AbstractThe removal of the main impurity CO2 is a crucial step in biogas upgrading. In this work, the separation of CO2 from CH4 on electrospun polyacrylonitrile-based carbon nanofibers (CNFs) is investigated using breakthrough experiments. The CNFs are prepared at various carbonization temperatures ranging from 600 to 900 °C and feature a tailorable pore size that decreases at higher carbonization temperatures. The adsorption properties of the different CNFs are studied measuring pure component isotherms as well as column breakthrough experiments. Adsorption kinetics are discussed using a linear driving force approach to model the breakthrough experiment and obtain the adsorption rate constant. Moreover, different approaches to determine the selectivity of the competitive CO2/CH4 adsorption are applied and discussed in detail. The results clearly prove that a size exclusion effect governs the adsorption selectivity on the CNFs. While CH4 cannot adsorb in the pores of CNFs prepared at 800 °C or above, the smaller CO2 is only excluded from the pores of CNFs prepared at 900 °C. For CNFs carbonized in the range from 600 to 750 °C, values of the CO2/CH4 selectivity of 11–14 are obtained. On the CNFs prepared at 800 °C the CH4 adsorption is severely hindered, leading to a reduced adsorbed amount of CH4 and consequently to an improved CO2/CH4 selectivity of 40. Furthermore, owing to the shrinking pores, the adsorption rates of CH4 and CO2 decrease with higher carbonization temperature.

Characterization and Mechanism Analysis of Flexible Polyacrylonitrile-Based Carbon Nanofiber Membranes Prepared by Electrospinning

Characterization and Mechanism Analysis of Flexible Polyacrylonitrile-Based Carbon Nanofiber Membranes Prepared by Electrospinning

Deposition of Pt Nanoparticles by Ascorbic Acid on Composite Electrospun Polyacrylonitrile-Based Carbon Nanofiber for HT-PEM Fuel Cell Cathodes

The efficient use of renewable energy sources requires development of new electrocatalytic materials for electrochemical energy storage systems, particularly fuel cells. To increase durability of high temperature polymer electrolyte fuel cell (HT-PEMFC), Pt/carbon black based catalysts should be replaced by more durable ones, for example Pt/carbon nanofibers (CNF). Here, we report for the first time the quantitative ascorbic acid assisted deposition of Pt onto electrospun polyacrylonitrile-based CNF composite materials. The effect of their subsequent post-treatment at various temperatures (250 and 500 °C) and media (vacuum or argon-hydrogen mixture) on the Pt/C catalyst morphology is investigated. All obtained samples are thoroughly studied by high resolution electron microscopy, and Pt electrochemically active specific surface area was evaluated by cyclic voltammetry.

Manganese ferrite decorated N-doped polyacrylonitrile-based carbon nanofiber for the enhanced capacitive deionization

In this study, the manganese ferrite was decorated onto 1-dimensional based activated carbon fiber (MnFe2O4/N-ACF) by precipitation method for capacitive deionization (CDI) application. Polyacrylonitrile (PAN) and 2-methylimidazole (2MI) were used as the carbon precursor and nitrogen dopant for the fabrication of 200 nm N-doped ACF (N-ACF). After the deposition of 5–15 wt% MnFe2O4 nanoparticles, the diameter of MnFe2O4/N-ACF increases to 300–400 nm, and the addition of 10 wt% MnFe2O4 can well deposits onto the surface of N-ACF to decrease the impedance to accelerate the electron transfer as well as to enhance the specific capacitance up to 422 F g−1 at 5 mV s−1. Furthermore, the CDI Ragone plots indicate that the specific electrosorption capacity (SEC) of NaCl by 10 wt% MnFe2O4/N-ACF is in the range of 23.4–41.2 mg g−1, which is a function of applied voltage, NaCl concentration, and flow rate. A SEC of 41.2 mg g−1 in the presence of 500 mg L−1 can be achieved when the flow rate and applied voltage are 10 mL min−1 and 1.4 V, respectively. Moreover, the as-prepared electrode materials can be recycled for at least 50 cycles and the SEC can be maintained over 93% of the original activity after 50 cycles, indicating the excellent cycling stability of MnFe2O4/N-ACF electrode. Results obtained in this study signify that the 1-D MnFe2O4/N-ACF is a promising CDI electrode material, which can provide a productive solution for elevating the platform with low cost and high efficiency for CDI technology.

Degradation of tetracycline/oxytetracycline by electrospun aligned polyacrylonitrile-based carbon nanofibers as anodic electrocatalysis microfiltration membrane

The treatment of antibiotic wastewater is a hot research topic now. To achieve a fast and efficient degradation effect, aligned polyacrylonitrile-based carbon nanofibrous (ACFs) membrane as anodic electrocatalysis microfiltration membrane was fabricated by high-speed electrospinning technology in this work. The morphology, structure, electrochemical performance and mechanical properties of ACFs membrane as anode filter were characterized. The high degrees of nanofiber alignment and carbonization are obtained at the rotating speed of 1500 r/min and the temperature of 900 ℃, respectively, which provides the ACFs membrane with good electrical conductivity and mechanical properties. The highest removal rate (nearly 80%) of tetracycline/oxytetracycline (TC/OTC) in mixture solution was obtained with 4 layers of ACFs membranes under the potential of 2.5 V at the initial concentration of 40 mg/L within the reaction time of 120 min. A decrease of removal rate by only 5% after 5 cycles of repeated experiments indicated good electrocatalytic activity and cycling stability of ACFs membrane. These results indicated that more than one antibiotic could be treated rapidly by ACFs membranes with a high removal rate in a short reaction time, and has great application prospects in the treatment of refractory antibiotic wastewater.

Structural Study of Polyacrylonitrile-Based Carbon Nanofibers for Understanding Gas Adsorption.

Polyacrylonitrile-based carbon nanofibers (PAN-based CNFs) have great potential to be used for carbon dioxide (CO2) capture due to their excellent CO2 adsorption properties. The porous structure of PAN-based CNFs originates from their turbostratic structure, which is composed of numerous disordered stacks of graphitic layers. During the carbonization process, the internal structure is arranged toward the ordered graphitic structure, which significantly influences the gas adsorption properties of PAN-based CNFs. However, the relation between structural transformation and CO2 capture is still not clear enough to tune the PAN-based CNFs. In this paper, we show that, with increasing carbonization temperature, the arrangement of the PAN-based CNF's structure along the stack and lateral directions takes place independently: gradually aligning and merging along the stack direction and enlarging along the lateral direction. Further, we correlate the structural arrangement and the CO2 adsorption properties of the PAN-based CNFs to propose a comprehensive structural mechanism. This mechanism provides the knowledge to understand and tailor the gas adsorption properties of PAN-based CNFs.

Design of a ductile carbon nanofiber/ZrB2 nanohybrid film with entanglement structure fabricated by electrostatic spinning

Polyacrylonitrile (PAN), a kind of multi-purpose man-made polymer material, has been widely used in various products, including carbon fiber precursor fiber manufacturing. Organic/inorganic nanocomposites can provide precursor material with unique properties due to optimal structural design. Herein, PAN based carbon nanofiber (CNF) coated zirconium borate (ZrB2) particles fiber film was prepared via electrostatic spinning strategy. Crosslinking network between carbon atoms formed at 280 °C due to long chain PAN molecules, which underwent pyrolysis at 800–1200 °C. Scanning electron microscope analysis showed that ductile CNF/ZrB2 hybrid material with entanglement structure was successfully fabricated. Phase composition of the materials was analyzed by X-ray diffractometer, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy, which confirmed the presence of carbon atoms in the materials. Entanglement structure between CNFs and ZrB2 enhanced tensile performance of nanohybrid film, in which CNF film with 25% ZrB2 content exhibited optimal mechanical properties. The design of nanohybrid structure provides facile and universal approach for exploration of organic/inorganic nanocomposites with controlled structures and excellent mechanical properties.

Polyacrylonitrile-based carbon nanofibers as a matrix for laser desorption/ionization time-of-flight mass spectrometric analysis of small molecules under both positive and negative ionization modes.

Carbon fiber (CNF), prepared by carbonization of electrospun polyacrylonitrile (PAN) fibers, is systematically investigated as a mediator to replace conventional organic matrices for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-MS). CNF exhibits a high salt tolerance, sensitivity, and resolution for organic matrix-free laser desorption/ionization time-of-flight mass spectrometry (LDI-MS) analysis of various analytes under both positive and negative ionization modes. Especially, saccharides, a neutral molecule having low negative ionization efficiency, are successfully detected with CNF. Taken together, this study clearly demonstrates CNF is a promising material to develop an efficient and universal platform for LDI-MS analysis regardless of preferential ionization modes of analytes. Graphical abstract.

Ultrathin honeycomb-like MnO2 on hollow carbon nanofiber networks as binder-free electrode for flexible symmetric all-solid-state supercapacitors

Carbon nanofiber-based supercapacitors hold great promise for powering wearable electronics due to their high specific density, fast charge/discharge rate and ultralong cycling life. However, the most common polyacrylonitrile-based carbon nanofiber (CNF) is fragile and easy to break, which limits their practical application. Herein, a poly(acrylonitrile-co-β-methylhydrogen itaconate) copolymer is synthesized and used as precursor to prepare flexible hollow carbon nanofiber (HCNF) by coaxial electrospinning, which can be bended freely without breaking. Then, the ultrathin honeycomb-like MnO2 is coated uniformly on the inner and outer surface of HCNF by in-situ reduction method to prepare freestanding flexible 3D HCNF/MnO2 networks. The HCNF/MnO2 electrode exhibits high capacity 587.5 F g−1 at 0.5 A g−1 and good cycling stability 78.96% retention after 5000 cycles. The HCNF/MnO2 composite is directly utilized to fabricate symmetric all-solid-state symmetric supercapacitors (ASSCs) without using any current collector or binders. The ASSC exhibits a maximum specific energy of 59.15 Wh kg−1 at a specific power of 1575 W kg−1. Four ASSC in series can power a ‘DHU’ Logo consisted of 36 light emitting diodes, confirming the lightweight flexible HCNF/MnO2 based flexible ASSCs have great potential application in wearable and portable electronics.

Carbonization of electrospun polyacrylonitrile (PAN)/cellulose nanofibril (CNF) hybrid membranes and its mechanism

Polyacrylonitrile (PAN)/cellulose nanofibril (CNF) based carbon nanofiber membranes were produced by electrospinning and carbonization method, in which the CNF amount was 1 wt%. In order to control the spinning process, the rheological properties of the PAN/CNF suspensions were measured before electrospinning. In addition, the effects of CNF particle size on the structure and properties of carbon nanofiber membranes were investigated systematically by SEM, FTIR and mechanical test. Meanwhile, the reaction mechanism of PAN and PAN/CNF nanofiber membranes in the process of stabilization and carbonization was also fully discussed. The results show that the addition of CNFs can improve the breaking strength and conductivity of PAN carbon nanofiber membrane. Moreover, CNFs also can accelerate the carbonization rate and reduce the reaction conditions of PAN nanofiber membranes. Therefore, CNFs are effective enhancers for PAN based carbon nanofiber membranes.

Nitrogen-doped carbon dots derived from electrospun carbon nanofibers for Cu(ii) ion sensing

Nitrogen-doped carbon dots were synthesized via the chemical breakdown of electrospun polyacrylonitrile-based carbon nanofibers and employed as a fluorescent sensing platform.

Optimization of the pore structure of PAN-based carbon fibers for enhanced supercapacitor performances via electrospinning

Activated microporous polyacrylonitrile-based carbon nanofibers (APCFs) were synthesized by a sequential process of electrospinning, carbonization, and KOH activation. The porosity and surface chemistry of the APCFs strongly depended on the activation temperature. The specific surface area and pore volume varied from 15 to 1886 m2 g−1 and 0.021–1.196 cm3 g−1, respectively, as the activation temperature increased; this was accompanied by morphology changes at high temperature. The dominant microstructure and minor mesostructure improved the capacitance of carbon. Compared to the other samples, APCFs activated at an optimum temperature of 1000 °C showed the highest specific capacitance of 103.01 F g−1 at 1 A g−1 in 1 mol L−1 Na2SO4 aqueous electrolyte, and an excellent cycling durability up to 3000 cycles. The improved electrochemical efficiency could be explained by the high specific surface area, suitable pore size, and influence of heteroatoms relative to the increased electrical double-layers. The change in the pore size distribution with activation temperature is also discussed in detail.

Facile synthesis of electrospun C@NiO/Ni nanofibers as an electrocatalyst for hydrogen evolution reaction

Hydrogen evolution reaction (HER) is considered to be one of the most important electrochemical reactions from both fundamental and application perspective to produce hydrogen. Polyacrylonitrile (PAN) based carbon (C)@NiO/Ni nanofibers were fabricated via simple electrospinning method. The as-prepared C@NiO/Ni nanofibers were characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy Energy Dispersive X-ray Spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectra. The SEM and TEM analyses revealed that NiO/Ni nanoparticles distributed on the PAN based carbon nanofibers. EDS, XPS and XRD results confirm the presence of the nanoparticles. The catalytic activity and durability of C@NiO/Ni nanofibers containing different weight ratio of Ni salt content (2%, 3%, & 4%) were examined for HER in 1 M KOH solution. It has been observed that C@NiO/Ni nanofibers containing Ni content (4%) showed the highest catalytic activity. It indicates that the catalytic activity of electrocatalyst can be enhanced by increasing the effective active sites. Noteworthy to mention here that the nanofibers catalyst reached a current density of 60 mA/cm2. The as-prepared catalyst showed remarkable stability up to 22 h and retained 99% of its initial activity even after 16 h of reaction.

Electronic, Magnetic, and Transport Properties of Polyacrylonitrile-Based Carbon Nanofibers of Various Widths: Density-Functional Theory Calculations

Spintronic devices require channels to efficiently conduct spin current. Carbon nanofibers based on polyacrylonitrile (PAN) are already of keen interest in nanotechnology and energy science; could they be useful in spintronics as well? Modeling PAN nanofibers as N-terminated zigzag graphene nanoribbons, the authors study the electronic structures and quantum transport properties of these quasi-one-dimensional systems as a function of width. They demonstrate that narrow ribbons bear finite magnetic moments, with spin-polarized electronic states exhibiting similar spin configurations on both edges, resulting in spin-dependent transport channels.

Optimum stabilization processing parameters for polyacrylonitrile-based carbon nanofibers and their difference with carbon (micro) fibers

Carbon nanofiber webs have high electrical and thermal conductivity, porosity and surface area, etc. making them favorable in many applications. In this paper, three types of polyacrylonitrile (PAN) copolymers are electrospun (average diameter of 150–500 nm) and carbon nanofibers are produced (average diameter of 110–300 nm). The effects of chemical composition and processing parameters on the formation of graphitic structure, morphology and electrical conductivity of the carbon nanofibers are studied. Unlike carbon fibers in micro scale, using PAN without acidic comonomers is suitable for production of carbon nanofibers. Common processing parameters for stabilization of PAN microfibers are not applicable to PAN nanofibers. Nanofibers stabilized using common microfibers procedure cannot tolerate high carbonization temperatures. While, thermal stabilization at higher temperature (300 °C) results in proper stabilized structure with ability to tolerate carbonization conditions. Progress of stabilization reactions higher than 98% is inappropriate for obtaining electrically conductive nanofiber webs, whereas 85–90% progress is considered adequate for development of proper structure during carbonization to obtain optimum electrical conductivity. Formation of nanofiber mats in shape of an interconnected sponge-like structure is believed to be necessary for obtaining much higher electrical conductivity (17–26 S/cm compared to 1–8 S/cm). Reducing fiber diameter from micro to nanoscale, the effect of processing parameters as well as the rate of thermochemical reactions can be different.

Facile fabrication of foldable electrospun polyacrylonitrile-based carbon nanofibers for flexible lithium-ion batteries

To enable electrospun polyacrylonitrile-based C nanofibers (CNFs) to be employed as anode materials in flexible Li-ion batteries, it is essential to overcome their frangibility and enhance their flexibility.

Carbon nanofiber yarns fabricated from co-electrospun nanofibers

Three different nanofiber yarns with various structures are first fabricated using a custom-made, coaxial, conjugate, electrospinning set-up. These yarns are then subjected to thermal stabilization and carbonization to obtain polyacrylonitrile-based carbon nanofiber yarns (PAN-based CNY), PAN/poly(methyl methacrylate)-based carbon nanofiber yarns (PAN/PMMA-based CNY), and C/Cu composite nanofiber yarns. The structures of the three CNYs are characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. The electrical conductivity of the samples is measured using a four-point probe method. In the case of the PAN-based CNY, the fibers strongly adhere to each other and eventually fracture, making the individual fibers no longer distinguishable from each other. On the other hand, the PAN/PMMA-based CNY and C/Cu composite nanofiber yarns are composed of independent fibers that are well oriented. Moreover, for the C/Cu composite nanofiber yarn, a nanowire composed of Cu nanoparticles is observed along the central axis of these fibers. In addition, Cu nanoparticles uniformly adhere to the surfaces of these fibers. Compared to the PAN-based CNY, the electrical conductivity of the C/Cu composite nanofiber yarns is significantly higher.

Enhanced Photocatalysis of Graphene and TiO2 Dual-Coupled Carbon Nanofibers Post-treated at Various Temperatures

Graphene and titanium dioxide (TiO2) were coupled to a conducting polymer substrate to generate graphene–TiO2 carbon nanofibers (GTCNs) using an electrospinning method with a post-thermal treatment process. The photocatalytic activities of GTCNs for the purification of selected toxic organic pollutants under visible-light illumination were higher than those of three reference photocatalysts (i.e., TiO2-, graphene-, and polyacrylonitrile-based carbon nanofibers). The photocatalytic activities of GTCNs increased with increasing treatment temperature from 300 to 400 °C and then decreased gradually with further increases to 500 and 600 °C, indicating that there is an optimum post-treatment temperature. The photocatalytic degradation efficiencies for the target pollutants over GTCNs post-treated at 400 °C under visible-light-emitting-diode (visible-LED) irradiation were lower than those obtained using a conventional daylight lamp. However, visible-LEDs were suggested as energy-potent photon sources for photoca...