Coated Carbon Nanofibers Research Articles

Mott Schottky heterojunction Co/CoSe2 electrocatalyst: Achieved rapid conversion of polysulfides and Li2S deposition dissolution via built-in electric field interface effect

Rechargeable lithium-sulfur (Li-S) batteries are considered ideal candidates for the next generation of energy storage devices. However, the insulation properties of S and Li2S, as well as the notorious “shuttle effect” of lithium polysulfide, result in severe loss of active sulfur, poor redox kinetics, and rapid capacity decline. To overcome these limitations, this paper designs a self-supporting electrocatalytic electrode based on Co/CoSe2 Mott Schottky heterojunction coated carbon nanofibers (Co/CoSe2@NCNFs), and engineers it for capturing and converting polysulfides. Density functional theory calculations show that the introduction of Co/CoSe2 heterojunction effectively reduces the redox barrier of Li2S. The electron current and electron interaction at the Co/CoSe2 interface induce the redistribution of charge density in the depletion region, thus increasing the chemical reactivity of the metal semiconductor heterojunction interface, which is conducive to the ion/electron transport, polysulfide conversion and Li2S oxidation process. Therefore, the Li-S battery assembled by Co/CoSe2@NCNFs/S electrode exhibited a high initial specific capacity of 1043.3 mAh/g at 1C, and maintained a capacity of 709.9 mAh/g after 1000 cycles, with a capacity decay rate of only 0.032% per cycle. The proposed Mott Schottky heterojunction as an electrocatalyst deepens the promotion of polysulfides and Li2S in long-life Li-S batteries.

Thermal Investigation and Kinetic Evaluation of CuO Coated Carbon Nanofibers in Hybrid Nanocomposite Energetic Composition

Nanomaterial additives have been broadly used in different applications to enhance the energy output of energetic materials. Herein, the carbon nanosized fibrous surfaces (CNF) were subjected to a pretreatment process followed by catalysis to ensure the successful deposition of a thin layer of nano-copper. The obtained Cu-coated layer was then galvanized at 250°C then sonicated with aluminum nanoparticles (120 nm average particle size), producing CuO-coated CNF nanosized thermit colloids in isopropanol. These colloids could act as a recommended oxidizer agent for Al nanoparticles. Finally, the obtained nanosized thermit colloids were combined with trinitrohexahydrotriazine (RDX) crystals. The impact of this combination on the RDX decomposition behavior was investigated utilizing the modified Kissinger-Akahira-Sunose (KAS) method. Interestingly, the average activation value was decreased by 40.5%, which could be attributed to the high reactivity of the developed thermite colloids together with a combination that occurred with RDX nitramine particles.

One-step synthesis of core–shell structured CNFs@CAC with excellent water wettability and oxidation resistance

The core–shell structured calcium aluminate cement coated carbon nanofibers (CNFs@CAC) with the same phase composition as Secar71 cement were synthesized to improve the water dispersion and oxidation resistance of carbon nanofibers. The FTIR spectroscopy showed that catalyst ferric chloride can catalyze the polymerization of the maleate. Raman spectroscopy indicated that the graphitization degree of the CNFs was the highest when the amount of catalyst was 0.5 wt%. The CNFs@CAC were characterized by SEM and HRTEM, the results showed that the length and the diameter of the CNFs were ∼ 500 µm and tens of nm, respectively. Carbon nanofibers agglomerates were wrapped in a compact ∼ 3–5 μm thick shell of calcium aluminate forming a core–shell structure. The growth mechanism of carbon nanofibers and the formation process of core–shell structure were studied. The DFT calculation suggested that iron atoms donated d-state electrons to C and O atoms weakening the strength of C-H and C≡O bonds and promoting the growth of CNFs. Calcium aluminate coated carbon nanofibers agglomerates was closely related to the formation of liquid phase calcium aluminate. Moreover, the CNFs@CAC had better water wettability and oxidation resistance compared with S71CB mixed by the same carbon content carbon black and Secar71 cement.

Fluorine-free anti-droplet surface modification by hexadecyltrimethoxysilane-modified silica nanoparticles-coated carbon nanofibers for self-cleaning applications

In daily life, many surfaces become contaminated owing to dust/dirt accumulation via air pollution. Self-cleaning surface modification is one of the best ways to address this problem. Therefore, ultra-hydrophobic coatings have garnered significant attention owing to their potential applications featuring water resistance and self-cleaning ability. In this study, a simple, fluorine-free, as well as eco-friendly technique was utilized to fabricate durable self-cleaning coatings. This coating material consists of fluorine-free hexadecyltrimethoxysilane-altered SiO2 nanoparticle (NPs)-coated carbon nanofibers (CNF/SiO2-HDTMS) and a commercial gelatin based adhesive emulsion. Owing to the presence of the hydroxyl (−OH) functional groups of CNFs, SiO2 NPs could accumulate on CNFs surface, hence creating hierarchical microstructures that generate air pockets for improved hydrophobicity. In this study, the developed coating was applied onto a polyethylene sheet, glass fiber membrane, and glass via dip coating. These surfaces were targeted due to over-use in day-to-day life as well as in industrial applications such as plastic tents, umbrellas, windshields of vehicles, window and door glasses, skyscrapers, membranes, fabrics, papers and the list is endless. Interestingly, after the introduction of the adhesive based CNF/SiO2-HDTMS coating, the superhydrophilic microfiber filter became highly hydrophobic, with a water contact angle of 125°. Similar effect can be seen in case of the modified glass, where the average contact angle was determined to be around 141°. The CNF/SiO2-HDTMS coated poly bag exhibited excellent anti-droplet behavior with water contact and rolling angles of 136° and 12°, respectively. The self-cleaning coatings maintained anti-droplet behavior even after tests such as sand impact abrasion, and finger touch. This study explores the possible industrial applications of self-cleaning coatings at ambient temperature to improve the feasibility of their usage.

Mesoporous silica coated carbon nanofibers reduce embryotoxicity via ERK and JNK pathways

Carbon nanofibers (CNFs) have been implicated in biomedical applications, yet, they are still considered as a potential hazard. Conversely, mesoporous silica is a biocompatible compound that has been used in various biomedical applications. In this regard, we recently reported that CNFs induce significant toxicity on the early stage of embryogenesis in addition to the inhibition of its angiogenesis. Thus, we herein use mesoporous silica coating of CNFs (MCNFs) in order to explore their outcome on normal development and angiogenesis using avian embryos at 3 days and its chorioallantoic membrane (CAM) at 6 days of incubation. Our data show that mesoporous silica coating of CNFs significantly reduces embryotoxicity provoked by CNFs. However, MCNFs exhibit slight increase in angiogenesis inhibition in comparison with CNFs. Further investigation revealed that MCNFs slightly deregulate the expression patterns of key controller genes involved in cell proliferation, survival, angiogenesis, and apoptosis as compared to CNFs. We confirmed these data using avian primary normal embryonic fibroblast cells established in our lab. Regarding the molecular pathways, we found that MCNFs downregulate the expression of ERK1/ERK2, p-ERK1/ERK2 and JNK1/JNK2/JNK3, thus indicating a protective role of MCNFs via ERK and JNK pathways. Our data suggest that coating CNFs with a layer of mesoporous silica can overcome their toxicity making them suitable for use in biomedical applications. Nevertheless, further investigations are required to evaluate the effects of MCNFs and their mechanisms using different in vitro and in vivo models.

Biomimetic and flexible 3D carbon nanofiber networks with fire-resistant and high oil-sorption capabilities

A facile and scalable approach to prepare multilayered graphene coated carbon nanofiber (G-CNF) foam has been demonstrated for oil/chemical solvent spill clean-up applications. 2D electrospun polyacrylonitrile/itaconic acid (PANIA) membrane was converted into a nature inspired three-dimensional (3D) aerogel networks self-assembled by a gas foaming method. The 3D nanofiber foams were then coated with Graphene Oxide (GO) and carbonised into G-CNF foam. These foams display highly interconnected network; mimicking the features of chicken feather and demonstrated the synergistic properties of graphene and carbon nanofibers. These 3D foams were light weight, resilient and exhibited fire-resistance properties. The design features of the G-CNF foams comprise of interconnected carbon nanofiber layers leading to high specific surface area that contributed towards oil and solvents sorption properties. The G-CNF foams perform high saturation sorption capacity (86–153 g g−1) toward a range of oils and organic solvents and demonstrated sustained sorption capabilities even after 11 cycles. In addition, the topology of the G-CNF surface and the morphology of the nanofiber foam were simulated and further studied using microstructure computational modelling and numerical analysis, which altogether showed that a significant enhancement in the surface area-to-volume ratio resulting from the coated graphene on the G-CNF foam.

Polyaniline nanoconical array on carbon nanofiber for supersensitive determination of nitrophenol

The polyaniline nanoconical array coated carbon nanofibers (PANI-array@CNF) were successfully fabricated by the polymerization of aniline monomers on the surface of the carbonized electrospun polyacrylonitrile fibers at low temperature. The morphology and electrochemical activity of the PANI-array@CNF are much dependent on the polymerization time and feeding speed of ammonium persulfate. In contrast with CNFs, the specific surface area and pore volume of the PANI-array@CNF become larger. Compared to commercial PANI powder, the oxidation/reduction response of PANI-array@CNF is dramatically enhanced due to the abundant active sites of the PANI nanoconical array perpendicular to the CNF surface. The PANI-array@CNF modified-glassy carbon electrode (PANI-array@CNF/GCE) exhibits outstanding electrochemical response to the reduction of o-nitrophenol (o-NP), m-nitrophenol (m-NP) and p-nitrophenol (p-NP). The PANI-array@CNF/GCE delivers a super-high detection sensitivity for individual analysis of nitrophenol isomers, with the limit of detection down to 0.5 nM for o-NP, 1.0 nM for m-NP and 1.5 nM for p-NP. In addition, the fabricated sensor has been successfully applied for the simultaneous determination of o-NP and p-NP in lake and tap water samples. The PANI-array@CNF based sensor has good repeatability, high stability and excellent selectivity. It demonstrates a great potential for highly sensitive determination of nitrophenols in environmental pollution system.

Graphene intercalated free-standing carbon paper coated with MnO2 for anode materials of lithium ion batteries

The composite of manganese dioxide (MnO2) with high theoretical capacity (1230 mAh g−1) and carbon nanofiber paper with high electrical conductivity is attracting attention as a next-generation battery anode material. This study proposes a facile route for coating mesoporous MnO2 on the carbon fiber by low-temperature reduction of KMnO4 and intercalating graphene into the carbon paper through vacuum filtration. The MnO2 coated carbon nanofiber (MOCNF) is synthesized in the form of paper, while maintaining the flexibility and strength with graphene intercalated between MOCNF papers. The resulting paper is applied for the lithium ion battery anode without any current collector, binder and conductor. This free-standing electrode has a discharge capacity of 945 mAh g−1 at 100 mA g−1 and shows a high discharge capacity of 545 mAh g−1 at 1000 mA g−1 even after 1000 cycles. This stable cycle performance originates from the mesoporosity of MnO2 and the intercalation of graphene, which accelerates the kinetics of redox reaction and mitigates the electrochemical isolation of MnO2 from the carbon nanofibers. This paper-type material can be a next-generation battery anode with considerable flexibility and capacity. Furthermore, the facile method of MnO2 coating and graphene intercalation can be applied to the other electrode synthesis.

A novel battery scheme: Coupling nanostructured phosphorus anodes with lithium sulfide cathodes

Lithium-ion batteries are approaching their theoretical limit and can no longer keep up with the increasing demands of human society. Lithium-sulfur batteries, with a high theoretical specific energy, are promising candidates for next generation energy storage. However, the use of Li metal in Li-S batteries compromises both safety and performance, enabling dendrite formation and causing fast capacity degradation. Previous studies have probed alternative battery systems to replace the metallic Li in Li-S system, such as a Si/Li2S couple, with limited success in performance. Recently, there is a focus on red P as a favorable anode material to host Li. Here, we establish a novel battery scheme by utilizing a P/C nanocomposite anode and pairing it with a Li2S coated carbon nanofiber cathode. We find that red P anode can be compatible in ether-based electrolyte systems and can be successfully coupled to a Li2S cathode. Our proof of concept full-cell displays remarkable specific capacity, rate and cycling performances. We expect our work will provide a useful alternative system and valuable insight in the quest for next generation energy storage devices.

A conductive polymer derived N-doped carbon nanofiber supported Li2S coating layer for Li–S batteries with high mass loading

The commercialization of Li2S as a potential candidate for lithium-sulfur cathode material is hampered due to its low electronic conductivity, the “shuttle effect” and the initial energy barrier. In this work, nanosized Li2S particles coated carbon nanofibers are prepared via a solution-based chemical method. Benefiting from this synthetic method, a uniform Li2S layer can be obtained without any agglomeration. Due to the small size of Li2S particles, a smaller energy barrier is observed in the first charging process, which means it is easier to activate the Li2S with a smaller cut-off voltage. In addition, the carbon nanofibers as matrixes could enhance the conductivity of cathode. Moreover, to verify the potential practical application of prepared materials, Li2S cathodes with high loading amount of active materials (∼3 mg cm−2) are prepared, which show excellent cycling and rate performance, delivering an initial specific capacity of 916.2 mA h g−1 at 0.1C, and 321 mA h g−1 capacity still can be reached at 2 C. This good performance can be attributed to the unique solution-based synthesis method, resulting in small and uniform Li2S particles coated on carbon nanofibers.

Rocking-chair capacitive deionization with flow-through electrodes

Flow-through Rocking-chair Capacitive Deionization system with ultrahigh desalination rate is built for the first-time, in which sodium-pre-intercalated MnO2 coated carbon nanofiber aerogels are employed as the flow-through electrode.

High-performance pseudocapacitor electrodes based on the flower-like nickel sulfide coated carbon nanofiber webs

Flower-shaped Ni3S2/Ni structures were synthesized on the surface of three-dimensional (3D) carbon fiber webs (CFWs) using electroless plating of Ni and subsequent sulfuration. The as-obtained product of this treatment was characterized using various techniques including scanning electron microscopy and X-ray diffraction, and was confirmed to indeed be Ni3S2/Ni-coated CFWs. Moreover, these webs were observed to have a unique architecture, consisting of a hierarchical porous structure with the flower-shaped morphology. This structure apparently enabled efficient ion diffusion and rapid electron transfer through the 3D CFW supports, as the Ni3S2/Ni-coated CFWs showed excellent electrochemical performances: a high areal capacitance of 240 mF/cm2 at current density of 1 mA/cm2, a high rate capability of 85.4% retention at current density of 15 mA/cm2, and good long-term stability (98% over 2000 cycles).

Wafer-scale on-chip synthesis and field emission properties of vertically aligned boron nitride based nanofiber arrays

One dimensional boron nitride (BN) nanomaterials with a high aspect ratio are of great interest due to their unique properties and potential applications. However, BN nanomaterials are generally difficult to synthesize. Here, we describe the creation of arrays of vertically aligned pure BN nanofibers and BN coated carbon nanofibers, fabricated on-chip via a straightforward template-assisted chemical conversion reaction. The template, a glassy carbon nanofiber array, is produced by plasma processing of conventional photoresists. The method is highly controllable, patternable, and scalable, and the final arrays can be fabricated over large areas with a controlled fiber length. We characterize the electron field emission properties of the BN-coated carbon nanofiber array and find a large field enhancement factor, low turn-on voltage, and good stability. The outstanding field emission performance results from the small tip size and high aspect ratio of the nanofiber as well as the high chemical stability and high thermal conductivity of the BN coating.

Novel Superthermite Nanocomposite Hybrid Material Based on CuO Coated Carbon Nanofibers for Advanced Energetic Systems

The surfaces of carbon nanofibers (CNFs) were first pretreated with a catalyst to enable metal deposition and subsequently coated with a nanoscale layer of copper through electroless deposition. The resulting Cu-coated CNF hybrid was annealed at 250 °C to obtain CuO-coated CNFs that were ultrasonically suspended with aluminum nanoparticles (100 nm) in isopropyl alcohol to produce nanothermite colloid; where CuO coating can act as an effective oxidizer for Al nanoparticles. The developed nanothermite colloid was integrated and effectively dispersed in molten tri-nitro toluene (TNT). This novel colloid offers an increase in TNT shock wave strength of by 26% using a ballistic mortar test. Moreover it offers an increase total heat release by 75% using DSC. This is the first time ever to report on nanothermite particles supported on CNFs for highly energetic systems.

Effective adsorptive removal of amoxicillin from aqueous solutions and wastewater samples using zinc oxide coated carbon nanofiber composite

Abstract This study reports the removal of amoxicillin from environmental water matrices using zinc oxide coated carbon nanofibers composite as an adsorbent. The structural and surface properties of zinc oxide coated carbon nanofiber composite were characterized using X-ray diffraction, scanning electron microscopy/energy dispersion x-ray spectroscopy, transmission electron microscopy, and Fourier transform infrared spectroscopy. The factors (sample pH and dosage) influencing the adsorption experiments were optimised using central composite design. Freundlich, Langmuir and Flory-Huggin isotherm models were used to study the adsorption isotherms. The results obtained revealed that the maximum adsorption capacity was up to 156 mg g−1. The kinetic studies demonstrated that the adsorption process was best described by pseudo-second-order model and the equilibrium data followed Langmuir isotherm model. The optimised batch method was then applied for the removal of amoxicillin in real wastewater samples. In addition, the zinc oxide coated carbon nanofibers nanocomposite was found to reusable up to fifteen cycles.

Synthesis and electrochemical performance of transition metal-coated carbon nanofibers as anode materials for lithium secondary batteries

In this study, transition metal coated carbon nanofibers (CNFs) were synthesized and applied as anode materials of Li secondary batteries. CNFs/Ni foam was immersed into 0.01M transition metal solutions after growing CNFs on Ni foam via chemical vapor deposition (CVD) method. Transition metal coated CNFs/Ni foam was dried in an oven at 80°C. Morphologies, compositions, and crystal quality of CNFs-transition metal composites were characterized by scanning electron microscopy (SEM), Raman spectroscopy (Raman), and X-ray photoelectron spectroscopy (XPS), respectively. Electrochemical characteristics of CNFs-transition metal composites as anodes of Li secondary batteries were investigated using a three-electrode cell. Transition metal/CNFs/Ni foam was directly employed as a working electrode without any binder. Lithium foil was used as both counter and reference electrodes while 1M LiClO4 was employed as the electrolyte after it was dissolved in a mixture of propylene carbonate:ethylene carbonate (PC:EC) at 1:1 volume ratio. Galvanostatic charge/discharge cycling and cyclic voltammetry measurements were taken at room temperature using a battery tester. In particular, the capacity of the synthesized CNFs-Fe was improved compared to that of CNFs. After 30 cycles, the capacity of CNFs-Fe was increased by 78%. Among four transition metals of Fe, Cu, Co and Ni coated on carbon nanofibers, the retention rate of CNFs-Fe was the highest at 41%. The initial capacity of CNFs-Fe with 670mAh/g was reduced to 275mAh/g after 30 cycles.

An ultrathin and continuous Li4Ti5O12 coated carbon nanofiber interlayer for high rate lithium sulfur battery

Abstract Severe capacity fading and poor high rate performance of lithium sulfur (Li–S) battery caused by “shuttle effect” and low conductivity of sulfur hampers its further developments and applications. Li4Ti5O12 (LTO) possesses high lithium ion conductivity, and it is also can be used as an active adsorbent for polysulfide. Herein, fine LTO particle coated carbon nanofibers (CNF) were prepared and a conductive network both for electron and lithium ion was built, which can greatly promote the electrochemical conversion of polysulfide and improve the rate performance of Li–S batteries. Meanwhile, a quantity of adsorption sites is constructed by defects of the surface of LTO-CNF membrane to effectively immobilize polysulfide. The multifunctional LTO-CNF interlayer could impede the shuttle effect and enhance comprehensive electrochemical performance of Li–S batteries, especially high rate performance. With such LTO-CNF interlayer, the Li–S battery presents a specific capacity of 641.9 mAh/g at 5 C rate. After 400 cycles at 1 C, a capacity of 618.0 mAh/g is retained. This work provides a feasible strategy to achieve high performance of Li–S battery for practical utilization.

Maximized specific activity for the methanol electrooxidation by the optimized PtRu-TiO2-carbon nano-composite structure

The kinetics of the methanol electrooxidation needs to be improved to increase the power density using a lower amount of noble metal catalysts (i.e., Pt and Ru) in direct methanol fuel cells (DMFC). PtRu nanoparticles (∼5 nm) supported on TiO2-nanoparticle (∼4 nm)-coated carbon nanofibers were proposed as an alternative active catalyst for the DMFC. The nano-sized TiO2 can provide a short distance of electron transport from PtRu (reaction site) to the carbon (current collector). At the composite catalyst, the activity enhancement by the PtRu-TiO2 interaction suggested the sufficient electron conductivity at the electrode. The maximized specific activity of the proposed catalyst was 3 times higher compared to that of the commercial PtRu/C. The pore structure of the catalyst was changed by the oxidation conditions due to gasification of the carbon, and the higher activity was obtained by the catalyst with the higher surface area of the micropores (>800 m2 g−1). However, the contribution of micropore would be a secondary effect to the activity. The maximized specific activity was obtained when the volumes of PtRu and TiO2 were similar for the almost same size (around 5 nm) of these particles suggesting that the number of contact points between the PtRu and TiO2 were optimized and the interaction between them was maximized. The PtRu-TiO2-carbon nano-composite catalyst has a high potential as an alternative catalyst as the anode of DMFC.

Preparation of V2O5-ZnO coated carbon nanofibers: Application for removal of selected antibiotics in environmental matrices

The removal of ciprofloxacin (CIPRO) and cinoxacin (CINO) antibiotics from wastewater was investigated using V2O5-ZnO coated carbon nanofibers (V2O5-ZnO@CNF) as an adsorbent. The V2O5-ZnO@CNF nanocomposite was characterized using characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy/energy dispersion x-ray spectroscopy (SEM/EDX), and UV–vis spectrophotometry. The characterization results revealed that the V2O5-ZnO nanoparticles were incorporated on the surface of carbon nanofibers. The effects of different experimental parameters such as adsorbent amounts, contact time, initial pH, that affect the removal process were optimized using response surface methodology based on Box-Behnken design. The optimum conditions were found to be 018 g, 6.5 and 20 min for the adsorbent amount, sample pH and contact time, respectively. Under optimized conditions, the maximum adsorption capacity was found to be 71.4 and 87.7 mg g−1 for cinoxacin and ciprofloxacin, respectively. In addition, the adsorption isotherms and kinetics were used to investigate the adsorption mechanism. The data followed the order: Langmuir (R2 = 0.09942–0.9996) > Dubinin-Radushkevich (R2 = 0.9257–0.9557 > Temkin (R2 = 0.79991–0.9132),> Flory-Huggins (R2 = 0.7432–0.8813) > Freundlich (R2 = 0.7057–0.7808). Furthermore, the data was better described by pseudo- second-order kinetics, this implied that the adsorption process was dominated by chemisorption process as the rate-limiting mechanism through sharing or exchange of electrons between adsorbent and CIPRO or CINO.

Tuning the High‐Temperature Wetting Behavior of Metals toward Ultrafine Nanoparticles

AbstractThe interaction between metal nanoparticles (NPs) and their substrate plays a critical role in determining the particle morphology, distribution, and properties. The pronounced impact of a thin oxide coating on the dispersion of metal NPs on a carbon substrate is presented. Al2O3‐supported Pt NPs are compared to the direct synthesis of Pt NPs on bare carbon surfaces. Pt NPs with an average size of about 2 nm and a size distribution ranging between 0.5 nm and 4.0 nm are synthesized on the Al2O3 coated carbon nanofiber, a significant improvement compared to those directly synthesized on a bare carbon surface. First‐principles modeling verifies the stronger adsorption of Pt clusters on Al2O3 than on carbon, which attributes the formation of ultrafine Pt NPs. This strategy paves the way towards the rational design of NPs with enhanced dispersion and controlled particle size, which are promising in energy storage and electrocatalysis.