Electrospun Carbon Fibers Research Articles

Preparation and one-step activation of nanoporous ultrafine carbon fibers derived from polyacrylonitrile/cellulose blend for used as supercapacitor electrode

In this work, nanoporous ultrafine carbon fibers have been fabricated by one-step activation of electrospun polyacrylonitrile (PAN)/cellulose acetate (CA) ultrafine fiber using ZnCl2 as an activation agent. CA, a renewable resource, was used to replace part of PAN as carbon precursor for electrospun carbon fibers. The effect of additive amount of CA on the microstructure of the ultrafine carbon fibers, including morphology, crystal structure, porosity, specific surface area and surface chemistry, has been investigated. The introduction of CA made an active role in improving structural stability and specific surface area. Both three-electrode and two-electrode test were conducted to evaluate capacitive performance of the ultrafine carbon fibers. And the correlation between electrochemical performance and structure of the carbon fibers was discussed. When CA/PAN mass ratio was 1:9, the ultrafine carbon fibers have the highest specific capacitance of 280 F/g. Such high specific capacitance should be due to combination of high content of surface functionality and wider pores.

Evaluation of CO2 adsorption capacity of electrospun carbon fibers with thermal and chemical activation

ABSTRACTThe use of urea was investigated as an alternative to the poisonous and expensive NH3 gas, commonly used for amination of adsorbents. First, we fabricated activated carbon nanofibers (AnFs) by electrospinning of urea‐doped polyacrylonitrile solution (N‐AnF). By increasing the activation temperature, the average specific surface area (SBET) and micropore volume (Vmicro) of pristine nFs improved from 27.3 to 300 m2/g and 0.004 to 0.13 cm3/g, respectively. Upon urea doping, both properties were further enhanced to 542 m2/g and 0.22 cm3/g, respectively. However, with chemical investigation via X‐ray photoelectron spectroscopy, we observed that the urea‐doping incorporated more of less desired quaternary‐N, along with other more basic and desirable N‐functionalities (i.e., nitrile, pyridinic, pyrrolic N) tethered. Based on the eventual CO2 adsorption results, we realized that average pore diameter (davg) is a limiting factor with regard to CO2 adsorption by AnFs; the lower the davg, the better the adsorption. Further examination via adsorption isotherm model fitting showed that CO2 molecules were homogenously collected in a monolayer pattern. However, three‐parameter model Redlich–Peterson model best fits the experimental data, suggesting that the adsorption is concentration‐driven and that it tends toward Langmuir rather than Freundlich at elevated concentration of CO2. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45534.

Electrospun Carbon Fiber/Ni–Co Composites as Binder-Free Anodes for Lithium-Ion Batteries

Binder-free anodes composed of electrospun carbon fibers were prepared for lithium-ion batteries. Nickel−cobalt binary hydroxide (Ni−Co(OH)2) was coprecipitated on the electrospun carbon fibers to form a hierarchical structure with Ni−Co(OH)2 nanoflakes vertically attached on the fiber surface. When the composite fibers were annealed in air, Ni−Co(OH)2 nanoflakes were converted to NiCo2O4 nanosheets at 300°C. Further increasing the annealing temperature to 400°C resulted in the aggregation of NiCo2O4 on the fiber surface, causing the loss of NiCo2O4 nanostructures. When used as anodes, the composite fibers exhibited the higher specific capacity than the pristine carbon fibers. This was attributed to the hierarchical structure of the composite fibers in which the high surface area and rich mesopores of Ni−Co compounds provided easily accessible ion transport across electrolyte/electrode interfaces and additional lithium storage, respectively. Additionally, Ni−Co compounds possessed the high theoretical capacities. By contrast, the interconnected carbon fibers served as a conductive path for charge transfer. They also acted as a buffer to alleviate the Ni−Co-compound volume expansion and contraction during discharging and charging. Among all the samples, the composite fibers annealed at 300°C exhibited the highest capacity of 734 mAh g−1 at a current density of 150 mA g−1.

An efficient method for assembling layered g-C3N4 nanosheets grow on 1D pore channels carbon fibers as a composite photocatalyst by ultrasound-assisted exfoliation and hydrothermal method

A composite catalyst that layered graphite carbon nitride (g-C3N4) nanosheets adhered on electrospun carbon fibers (CFs) carrier was prepared, and this catalyst occupied the efficient photocatalytic activity. The carbon fiber was obtained through electrospinning technology and high-temperature calcination process. The layered g-C3N4 nanosheets was derived through the direct heating and ultrasonic exfoliation. After that, the g-C3N4/CFs were successfully synthesized in the hydrothermal process. In the process of degradation, composites had the capacity of degradation to different organic dyes under the UV-light irradiation, meanwhile, catalyst had excellent capacity of adsorption and a certain recycling performance. Thus, g-C3N4/CFs catalyst has potential appliance value in the degradation of organic pollutants.

Nickel and nickel phosphide nanoparticles embedded in electrospun carbon fibers as favourable electrocatalysts for hydrogen evolution

The needle-less electrospinning method is used for a preparation of carbon, carbon/nickel, carbon/nickel/nickel phosphides and carbon/nickel phosphides fibers of a continual length and a high specific surface area. The prepared fibers were produced in a large scale as a potential electrode material for electrocatalytic hydrogen evolution reaction (HER). The polyacrylonitrile (PAN) was used for a preparation of spun solution and subsequent precursor fibers formation. The phosphoric acid of 0.5 or 5wt% was added to the spun solution in order to increase conductivity of the spun solution as well as to provide a source of phosphorus in the final fibers. The exactly defined temperature schedules of calcinations and atmosphere were suggested according to the results obtained from TG/DSC analysis. The phosphoric acid in the electrospun PAN precursor fibers is responsible for the cyclization and aromatization during stabilization of the electrospun precursor fibers. The XRD analysis confirmed the formation of phosphides at different molar ratio of NiCl2:H3PO4. The final morphology, porosity and position of the incorporated nickel or nickel phosphides nanoparticles can be designed by the calcinations temperature and used atmosphere. A possible mechanism for a formation of nickel, nickel/nickel phosphide and nickel phosphide nanoparticles was suggested. The linear sweep voltammetry, impedance spectroscopy and Tafel slopes measured in 0.5M H2SO4 solution confirmed that the highest HER activity exhibit carbon fibers containing the nickel and nickel phosphide nanoparticles after the heat treatment in the hydrogen reduction atmosphere.

One-step solvothermal synthesis of Au-TiO2 loaded electrospun carbon fibers to enhance photocatalytic activity

Au-TiO2/CNFs composite materials were fabricated by electrospinning, high-temperature calcination, and solvothermal synthesis. After the one-step solvothermal synthesis, both gold and TiO2 nanoparticles were loaded on the surface of carbon nanofibers simultaneously. A series of characterizations including SEM, TEM, XRD and XPS were carried out to investigate the physicochemical properties of the as-prepared samples. The as-prepared Au-TiO2/CNFs exhibited a much higher photocatalytic activity than TiO2/CNFs in degrading MO, MB, and AR 18 under UV light irradiation, in which TiO2/CNFs sample was fabricated by the same procedures without the addition of Chloroauric acid. Moreover, the cycling tests demonstrated that Au-TiO2/CNFs had an excellent stability. This work offered a new idea on the modification and immobilization of titanium dioxide and the as-prepared Au-TiO2/CNFs has a potential application in sewage treatment and selective oxidation, etc.

One‐Pot Route to Gold Nanoparticles Embedded in Electrospun Carbon Fibers as an Efficient Catalyst Material for Hybrid Alkaline Glucose Biofuel Cells

AbstractTraditional strategies to develop Au metal nanoparticle catalysts for glucose oxidation comprise Au nanoparticles (NPs) supported on electrode surfaces. In this work, the fabrication of a new material capable of acting as an abiotic anode for the electrooxidation of glucose was developed. The material is composed of electrospun carbon fibers containing gold nanoparticles formed in situ from a polyacrylonitrile (PAN) solution with HAuCl4. This approach allows the pre‐reduction of the gold salt by PAN under mild conditions without the need for extra energy and leads to very stable carbon–gold bonding with well‐dispersed AuNPs, not previously reported. The gold‐modified carbon fibers (Au@CFs) were characterized by SEM, energy‐dispersive X‐ray spectroscopy, XRD, and electrochemical analysis. The Au@CF electrodes showed electrochemical activity toward glucose oxidation in alkaline media. Combined to a bilirubin oxidase modified biocathode (BOD@CFs), the resulting hybrid glucose biofuel cell showed open‐circuit voltage and power density values of 0.75 V and 65 μW cm−2, respectively, which remained intact after 3 weeks.

The controllable preparation of electrospun carbon fibers supported Pd nanoparticles catalyst and its application in Suzuki and Heck reactions

Abstract The palladium nanoparticles/carbon nanofibers (Pd NPs/CNFs) catalyst was prepared by the electrospinning method, the hydrazine hydrate solution reduction in an ice bath environment, the high temperature carbonization. The catalyst was characterized by X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), and transmission electron microscopy (TEM). The nanofibers are not cross-linked and arranged in order. The surface of Pd NPs/CNFs is smooth, and it can be observed that a large number of particles were loaded and well-dispersed in carbon fiber matrix, and the particle distribution is uniform. The activity center of catalyst is Pd(0). The Pd NPs/CNFs exhibited a high efficiency, good reusability and stability in the Suzuki and Heck reactions. It can be used for at least five consecutive runs without significant loss of its catalytic activity. The good recyclability of Pd NPs/CNFs provides a way to greatly reduce the cost of the catalyst.

Are Electrospun Carbon/Metal Oxide Composite Fibers Relevant Electrode Materials for Li-Ion Batteries?

Self-standing and flexible paper-like electrodes consisting of nano-sized Co3O4 nanoparticles encapsulated in nitrogen-doped graphite-like carbon fibers are synthesized by electrospinning followed by thermal treatment. Several studies have recently reported that encapsulating nano-sized metal oxides that display conversion reaction, such as manganese, iron and cobalt oxides, within the three-dimensional network of electrospun carbon fibers allows to remarkably improve the performances of lithium-ion batteries. In the present work, we challenge these reports with a study based on the optimization of the preparation and post-synthesis treatment parameters, and a very precise characterization of the structural, morphological and chemical properties of the composite materials leading to clear structure-electrochemical properties correlations. In particular, it is found that the electrochemical properties of a physical mixture of cobalt oxide nanoparticles and electrospun carbon nanofibers are equivalent to the ones of the electrospun nanocomposites, proving that the benefit of electrospun metal oxide-carbon nanocomposites is limited and that the “enhanced properties” claimed in the literature arise from imprudent comparisons.

Processing and characterization of low-cost electrospun carbon fibers from organosolv lignin/polyacrylonitrile blends

The esterification of lignin with butyric anhydride decreases both the viscosity of lignin/PAN blend spinning solutions and their glass-transition temperature compared to unmodified lignin/PAN blends. The effect of blending PAN with lignin before or after butyration on the electrospinnability, miscibility and thermal stability of precursor blend fibers was investigated by morphological, rheological, and thermal analysis. The micromorphology, carbon structure, and mechanical properties of resultant carbonized fibers (CFs) were further evaluated. This study reveals a new approach to controlling inter-fiber bonding of lignin-based carbon nanofiber mats by manipulating the molecular structure of lignin while following a standard procedure of thermo-stabilization and carbonization treatment. Characterization results indicate that inter-fiber bonding in electrospun CF mats, induced by the high thermal mobility of butyrated lignin, favorably affected their mechanical properties.

Advances in electrospun carbon fiber-based electrochemical sensing platforms for bioanalytical applications.

Electrochemical sensing is an efficient and inexpensive method for detection of a range of chemicals of biological, clinical, and environmental interest. Carbon materials-based electrodes are commonly employed for the development of electrochemical sensors because of their low cost, biocompatibility, and facile electron transfer kinetics. Electrospun carbon fibers (ECFs), prepared by electrospinning of a polymeric precursor and subsequent thermal treatment, have emerged as promising carbon systems for biosensing applications since the electrochemical properties of these carbon fibers can be easily modified by processing conditions and post-treatment. This review addresses recent progress in the use of ECFs for sensor fabrication and analyte detection. We focus on the modification strategies of ECFs and identification of the key components that impart the bioelectroanalytical activities, and point out the future challenges that must be addressed in order to advance the fundamental understanding of the ECF electrochemistry and to realize the practical applications of ECF-based sensing devices.

Graphene: Sulfonated Graphene as Cation‐Selective Coating: A New Strategy for High‐Performance Membrane Capacitive Deionization (Adv. Mater. Interfaces 16/2015)

A new strategy for high performance membrane capacitive deionization (MCDI) is reported in article 1500372 by G. Wang, J. Qiu, and co-workers. A novel graphene-based cation-selective coating material over film-like electrospun carbon fibers is designed. The composites function to minimize the co-ion expulsion effect, common in traditional CDI processes, leading to an enhanced electrosorption capacity and an improved charge efficiency. This may open up a new avenue for high-performance, energy-efficient and cost-effective MCDI, and for wide applications of functional graphene-based materials.

Diameter effect of electrospun carbon fiber support for the catalysis of Pt nanoparticles in glucose oxidation

Electrospun carbon fibers (CFs) with diameters of 39nm (CF39nm), 158nm (CF158nm), and 309nm (CF309nm) were used as Pt-catalyst supports for a glucose oxidation reaction. Based on experimentally balanced comparisons using electrochemical methods, CF39nm with higher curvature and smaller diameter had a greater number of Pt atoms on the surface. Compared with the CF158nm and CF309nm systems, CF39nm has a higher electrochemically real surface area and greater catalytic activity on glucose oxidation. The Tafel analyses demonstrated that the exchange current density from an early rest potential (−0.81V) for the CF39nm system was 9.08×10−3mAcm−2, greater than 8.41×10−3mAcm−2 for CF158nm-supported Pt nanoparticles and 7.39×10−3mAcm−2 for CF309nm-supported Pt nanoparticles. In addition, as data supporting the catalytic characterization for glucose oxidation, all of the CF-supported Pt nanoparticles showed remarkable tolerance to foreign substances in the application of a non-enzymatic glucose sensor, where CF39nm-supported Pt nanoparticles (Pt/CF39nm) showed a higher sensitivity (2.03μAmM−1cm−2), detection limit (33μM), and linear range (0.3–17mM). The high recovery by serum sample analyses further confirmed the potential of Pt/CF39nm as a glucose sensor. The promising results showed the feasibility of these electrospun CFs being applied for both glucose fuel cells and non-enzymatic glucose sensors.

Electrospun Carbon Fibers: Promising Electrode Material for Abiotic and Enzymatic Catalysis

Carbon nanofibers (CNFs) are a promising material as conducting support of catalysts in (bio)electrochemical applications. Self-standing CNFs result from the carbonization at 1200 °C of electrospun polymer fibers with mean fiber diameter of 330 ± 50 nm. Such felts present interesting properties like fibrous and porous morphology to relieve the mass-transfer limitation of substrates and to provide high loadings of catalysts to enhance the electrochemical performances of the resulting electrodes. We show the beneficial feature of the CNFs as support compared with carbon dense structure for efficient immobilization of either abiotic catalysts based on metal nanoparticles or enzyme as biological catalyst. More specifically, palladium or platinum modified gold nanocatalysts remarkably boost the glucose electro-oxidation when deposited onto CNFs. Similarly, the immobilization of the bilirubin oxidase enzyme on the porous CNFs induces significant improvement of the mediated oxygen electroenzymatic reduction. The...

A Flexible Quasi‐Solid‐State Asymmetric Electrochemical Capacitor Based on Hierarchical Porous V2O5 Nanosheets on Carbon Nanofibers

The development of 3D nanoarchitectures on flexible current collectors has emerged as an effective strategy for preparing advanced portable and wearable power sources. Herein, a flexible and efficient electrode is demonstrated based on electrospun carbon fibers (ECF) substrate with elaborately designed hierarchical porous V2O5 nanosheets (V2O5–ECF). The unique configuration of V2O5–ECF composite film fully enables utilization of the synergistic effects from both high electrochemical performance of V2O5 and excellent conductivity of ECF, endowing the films to be an excellent electrode for flexible and lightweight electrochemical capacitors (ECs). Benefiting from their intriguing structural features, V2O5–ECF and ECF films, directly used as electrodes for flexible asymmetric quasi‐solid‐state electrochemical capacitors, achieve superior flexibility and reliability, enhanced energy/power density, and outstanding cycling stability. Moreover, the ability to power light‐emitting diodes (LED) also indicates the feasibility for practical use. Therefore, it is believed that this novel design may find promising application in flexible devices in future.

Electrospun Carbon Nanofiber Supports for Bioelectrodes

A high surface-area electrospun carbon nanofiber (CNF) support for bioelectrodes is introduced to enhance enzyme utilization.1 This study employed Glucose Oxidase (GOx) in redox hydrogel system, which mediated electron transfer via Osmium (Os2+/Os+) centers, to create a glucose bioelectrode. The strategy was to enhance the transport of electrons via the redox mediator by reducing the average hydrogel thickness at fixed hydrogel volume. The tunable electrospun carbon fiber enables of hydrogel film thickness of hydrogel film by uniform distribution on small fibers. Glucose oxidizing current density made from electrospun carbon nanofiber and several commercial counterparts suggest a possibility for a cheap fibers, in a diameter range below100 nm, that enable high current density (~8.5 mA cm-2) comparable to carbon nanotubes (CNTs). To adjust electrospun CNF size, varied concentrations of Polyacrylonitrile (PAN)/ Dimethylformamide (DMF) precursor solution (7 wt% to 14 wt%) was spun in a high voltage field prior to oxidation stabilization and carbonization in Argon environment at two temperatures, 850°C and 1100°C.2 Graphiticity of CNFs was improved with the increasing heat treatment temperature (shown by Raman spectroscopy), leading to higher conductivity of bioelectrode. CNFs based on 7 wt% PAN/DMF carbonized at 1100°C had a diameter of 150 nm (Figure 1b), a decrease from the 250 nm PAN fiber (Figure 1a), and showed good performance in electrochemical characterization compared to MWCNTs electrode (Figure 2). Acknowledgement We thank Buckeye Composites Inc. and Pyrograf Products Inc. for providing material samples. Reference (1) Wen, H.; Nallathambi, V.; Chakraborty, D.; Calabrese Barton, S. Carbon Fiber Microelectrodes Modified with Carbon Nanotubes as a New Support for Immobilization of Glucose Oxidase. Microchim. Acta 2011, 175, 283–289. (2) Bhardwaj, N.; Kundu, S. C. Electrospinning: A Fascinating Fiber Fabrication Technique. Biotechnol. Adv. 2010, 28, 325–347. Figure 1

Control of Spatial Organization of Electrospun Fibers in a Carbon Felt for Enhanced Bioelectrode Performance

Invited for this month's cover are collaborating researchers from the DM3 group at the European Membrane Institute of Montpellier, France. The cover picture shows an artistic view of the bioelectrochemical production of sustainable electricity. Laccase enzymes immobilized on aligned electrospun carbon fibers can efficiently reduce dissolved oxygen, and be used in the cathode compartment of an electrical biogenerator. Read the full text of the article at 10.1002/cplu.201402324.

Laccase wiring on free-standing electrospun carbon nanofibres using a mediator plug.

Electrospun carbon nanofibres (CNFs) containing CNTs were produced by electrospinning and subsequent thermal treatment. This material was evaluated as a bioelectrode for biofuel cell applications after covalent grafting of laccase. Bis-pyrene-modified ABTS was used as a plug to wire laccase to the nanofibres leading to a maximum current density of 100 μA cm(-2).

Control of Spatial Organization of Electrospun Fibers in a Carbon Felt for Enhanced Bioelectrode Performance.

Electrospun carbon fiber electrodes showing high performance for bio-electrochemical applications were developed. Easy to handle and manipulate aligned and unaligned carbon fibers with a mean diameter of (330±50) nm were synthesized through an electrospinning technique. Electrical resistivity measurements, which are a challenge that has not been much explored in the case of fibrous materials, were realized through two different techniques, and a study of contact resistances between electrical clips and the carbon fibers was performed. To target the creation of a bioelectrode, carbon fibers were characterized electrochemically by cyclic voltammetry. After being modified with the enzyme laccase, its response to oxygen electroreduction was studied. Aligned fibers present a cathodic current that is 30 % higher than that of randomly distributed fibers. Overall, the results show that aligned fibers are more appropriate for bio-electrochemical applications when exploiting anisotropic spatial organization.

The electrochemical enzymatic glucose biosensor based on mesoporous carbon fibers activated by potassium carbonate

Glucose-sensing electrodes have fabricated using mesoporous electro-spun carbon fibers, which have mesopores mainly and more oxygen functional groups on the surface, activated by potassium carbonate (K2CO3) with different concentrations. These porosity and the functional groups on the carbon fibers affected the immobilization of glucose oxidase on the electrode. The sensitivity of the electrode is determined based on enzymatic activity increasing glucose concentrations and calculated by enzyme kinetics using the Michaelis–Menten equation. The electrode prepared from carbon fibers activated with 4MK2CO3, which has the highest mesopore volume and specific surface area, has the sensitivity 3.4μAmM−1cm−2 and the broad linear range of up to 20mM.