Structure Of CNF Research Articles

Preparation of Effective NiCrPd-Decorated Carbon Nanofibers Derived from Polyvinylpyrrolidone as a Catalyst for H2 Generation from the Dehydrogenation of NaBH4.

The catalytic dehydrogenation of NaBH4 for the generation of H2 has a lot of potential as a reliable and achievable approach to make H2, which could be used as a safe and cost-effective energy source in the near future. This work describes the production of unique trimetallic NiCrPd-decorated carbon nanofiber (NiCrPd-decorated CNF) catalysts using electrospinning. The catalysts demonstrated exceptional catalytic activity in generating H2 through NaBH4 dehydrogenation. The catalysts were characterized using SEM, XRD, TEM, and TEM-EDX analyses. NiCrPd-decorated CNF formulations have shown higher catalytic activity in the dehydrogenation of NaBH4 compared with NiCr-decorated CNFs. It is likely that the better catalytic performance is because the three metals in the NiCrPd-decorated CNF structure interact with each other. Furthermore, the NiCrPd-decorated CNFs catalyzed the dehydrogenation of NaBH4 with an activation energy (Ea) of 26.55 KJ/mol. The kinetics studies showed that the reaction is first-order dependent on the dose of NiCrPd-decorated CNFs and zero-order dependent on the concentration of NaBH4.

Thin-Film SiOx Coated Carbon Nanofibers As Stable Anodes for Lithium-Ion Batteries

With the increase in the capacity of cathode materials in lithium-ion batteries(LIBs), the demand for novel anode materials with high theoretical energy density is following. Up to now, many candidates have been reported; silicon-based composites are considered a prospective alternative due to their abundant reserves and high energy density. However, The primary disadvantage of Si, electrochemical irreversibility during the charge/discharge process, hinder widespread use.In this study, we adapted SiOx-coated carbon nanofibers (SiOx-CNFs) composite to the binder-free anode current collector for lithium-ion batteries. The composite has a structure where a thin amorphous SiOx (thickness ~100nm) is coated on the CNFs surface and is successfully synthesized by electrospinning and sputtering. This structure, surface SiOx-coated porous CNF, breaks through the significant drawback of Si-based composites, pulverization of Si element during the charge/discharge cycle. In addition to this, due to the structure of porous CNF, we achieved the curtail of electrode weight.Scanning Electron Microscopy (SEM) and X-ray diffraction (XRD) analyses are carried out to confirm the morphology and crystallinity. Furthermore, with cyclic voltammetry analysis, fast reaction kinetics and excellent electrochemical reversibility are verified. The cycle test is also conducted to prove excellent capacity and cyclic stability.

Electrospun polyethylenimine (PEI)-derived nitrogen enriched carbon nanofiber for supercapacitors with artificial neural network modeling

This paper presents the utilization of polyethylenimine (PEI) polymer to obtain freestanding, binder-free, and nitrogen- enriched carbon nanofibers (NCNFs) by electrospinning which is an easy and fast method. The PEI polymer played a significant role as a poring agent for the adjustment of surface area and as the heteroatom doping to increase conductivity. NCNFs-10 electrode exhibited a specific capacitance of 200 F/g at 1 A/g with a good retention of 84.25 % at 10 A/g in three electrode system. The assembled supercapacitor had a specific energy of 5.57 Wh/kg at 125 W/kg with a good cycling performance of 80.5 % after 10,000 cycles. Furthermore, an artificial neural network (ANN) method was utilized to understand the relationship between the CNF's structure and supercapacitor performance by modeling the specific capacitance. The input factors were specific surface area (SBET), nitrogen doping (N% at), graphitization degree (ID/IG), internal resistance (Rs), pore size (Vpor), micropore volume (Vmic), the average diameter (Dave), and mesopore volume (Vmeso). Results showed that the first three remarkable variables are SBET, N (%at), and ID/IG.

Nanocellulose-based membrane as a potential material for high performance biodegradable aerosol respirators for SARS-CoV-2 prevention: a review.

The controversy surrounding the transmission of COVID-19 in 2020 has revealed the need to better understand the airborne transmission route of respiratory viruses to establish appropriate strategies to limit their transmission. The effectiveness in protecting against COVID-19 has led to a high demand for face masks. This includes the single-use of non-degradable masks and Filtering Facepiece Respirators by a large proportion of the public, leading to environmental concerns related to waste management. Thus, nanocellulose-based membranes are a promising environmental solution for aerosol filtration due to their biodegradability, renewability, biocompatibility, high specific surface area, non-toxicity, ease of functionalization and worldwide availability. Although the technology for producing high-performance aerosol filter membranes from cellulose-based materials is still in its initial stage, several promising results show the prospects of the use of this kind of materials. This review focuses on the overview of nanocellulose-based filter media, including its processing, desirable characteristics and recent developments regarding filtration, functionalization, biodegradability, and mechanical behavior. The porosity control, surface wettability and surface functional groups resulting from the silylation treatment to improve the filtration capacity of the nanocellulose-based membrane is discussed. Future research trends in this area are planned to develop the air filter media by reinforcing the filter membrane structure of CNF with CNCs. In addition, the integration of sol–gel technology into the production of an air filter can tailor the pore size of the membrane for a viable physical screening solution in future studies.Graphical abstract

Optical Properties of Cellulose Nanofibre Films at High Temperatures

Nanocelluloses and their different designs, such as films and nanopapers, have gained considerable interest in many application areas due to their unique properties. For many purposes, such as packaging and electronics, the thermal stability and optical properties of nanocellulose materials are crucial characteristics. In this study, the effects of heat treatment (100 ºC, 150 ºC and 200 ºC) on the optical and mechanical properties of 2,2,6,6-tetramethylpiperidinyl-1-oxy radical-oxidised cellulose nanofibre (TO-CNF) films were investigated, especially the alteration of the colour, complex refractive index and birefringence. Exposing TO-CNF films to high temperatures (> 150 ºC) induced permanent transformations in the CNF structure, leading to an increase in the refractive index, decreases in the birefringence and crystallinity index, colour darkening and significant deterioration of the mechanical properties.Graphical abstract

Synthesis and Electrochemical Performance of Electrostatic Self-Assembled Nano-Silicon@N-Doped Reduced Graphene Oxide/Carbon Nanofibers Composite as Anode Material for Lithium-Ion Batteries.

Silicon-carbon nanocomposite materials are widely adopted in the anode of lithium-ion batteries (LIB). However, the lithium ion (Li+) transportation is hampered due to the significant accumulation of silicon nanoparticles (Si) and the change in their volume, which leads to decreased battery performance. In an attempt to optimize the electrode structure, we report on a self-assembly synthesis of silicon nanoparticles@nitrogen-doped reduced graphene oxide/carbon nanofiber (Si@N-doped rGO/CNF) composites as potential high-performance anodes for LIB through electrostatic attraction. A large number of vacancies or defects on the graphite plane are generated by N atoms, thus providing transmission channels for Li+ and improving the conductivity of the electrode. CNF can maintain the stability of the electrode structure and prevent Si from falling off the electrode. The three-dimensional composite structure of Si, N-doped rGO, and CNF can effectively buffer the volume changes of Si, form a stable solid electrolyte interface (SEI), and shorten the transmission distance of Li+ and the electrons, while also providing high conductivity and mechanical stability to the electrode. The Si@N-doped rGO/CNF electrode outperforms the Si@N-doped rGO and Si/rGO/CNF electrodes in cycle performance and rate capability, with a reversible specific capacity reaching 1276.8 mAh/g after 100 cycles and a Coulomb efficiency of 99%.

Hybrid nanocomposites of tunneled-mesoporous sulfur-doped carbon nanofibers embedded with zinc sulfide nanoparticles for ultrafast lithium storage capability

As effective and simple approach by which to construct hybrid nanocomposite using ZnS nanoparticles (NPs) and conducting carbon materials to realize robust ultrafast lithium storage capabilities, we newly developed tunneled-mesoporous S-doped carbon nanofibers (SCNF) embedded with ZnS NPs through a one-pot carbonization process via the thiourea effect. This hybrid nanocomposite is unique given its tunneled-mesoporous CNF structure with well-dispersed ZnS NPs by ZnO sulfurization, offering available space to accept abrupt structural expansions of ZnS NPs and efficient Li-ion pathways during the electrochemical reaction. Using this material leads to competitive cycling stability and superior rate capabilities. Even at a high current density of 2000 mA g−1, amazing ultrafast electrochemical performance outcomes with a high specific capacity (391.8 mAh g−1) and good long-term cycling stability (97.2%) after 500 cycles were noted. These findings are attributed to the synergistic effects of the accelerated the transportation of Li ions for the ZnS NPs by the internal construction of the tunneled-mesoporous SCNF and facilitation of the electrical conductivity of the electrode via the S doping effect of the CNF matrix. Therefore, the proposed approach for a unique hybrid nanocomposite holds great potential regarding the development of an outstanding anode electrode to enhance the ultrafast lithium storage capabilities.

Effective Removal of Pb(II) Ions by Electrospun PAN/Sago Lignin-based Activated Carbon Nanofibers.

Heavy metal pollution, such as lead, can cause contamination of water resources and harm human life. Many techniques have been explored and utilized to overcome this problem, with adsorption technology being the most common strategies for water treatment. In this study, carbon nanofibers, polyacrylonitrile (PAN)/sago lignin (SL) carbon nanofibers (PAN/SL CNF) and PAN/SL activated carbon nanofibers (PAN/SL ACNF), with a diameter approximately 300 nm, were produced by electrospinning blends of polyacrylonitrile and sago lignin followed by thermal and acid treatments and used as adsorbents for the removal of Pb(II) ions from aqueous solutions. The incorporation of biodegradable and renewable SL in PAN/SL blends fibers produces the CNF with a smaller diameter than PAN only but preserves the structure of CNF. The adsorption of Pb(II) ions on PAN/SL ACNF was three times higher than that of PAN/SL CNF. The enhanced removal was due to the nitric acid treatment that resulted in the formation of surface oxygenated functional groups that promoted the Pb(II) ions adsorption. The best-suited adsorption conditions that gave the highest percentage removal of 67%, with an adsorption capacity of 524 mg/g, were 40 mg of adsorbent dosage, 125 ppm of Pb(II) solution, pH 5, and a contact time of 240 min. The adsorption data fitted the Langmuir isotherm and the pseudo-second-order kinetic models, indicating that the adsorption is a monolayer, and is governed by the availability of the adsorption sites. With the adsorption capacity of 588 mg/g, determined via the Langmuir isotherm model, the study demonstrated the potential of PAN/SL ACNFs as the adsorbent for the removal of Pb(II) ions from aqueous solution.

Flexible Membrane Consisting of MoP Ultrafine Nanoparticles Highly Distributed Inside N and P Codoped Carbon Nanofibers as High-Performance Anode for Potassium-Ion Batteries.

Rechargeable potassium-ion batteries (PIBs) have attracted tremendous attention as potential electrical energy storage systems due to the special merit of abundant resources and low cost of potassium. However, one critical barrier to achieve practical application of PIBs has been the lack of suitable electrode materials. Here, a novel flexible membrane consisting of N, P codoped carbon nanofibers decorated with MoP ultrafine nanoparticles (MoP@NPCNFs) is fabricated via a simple electrospinning method combined with the later carbonization and phosphorization process. The 3D porous CNF structure in the as-synthesized composite can shorten the transport pathways of K-ions and improve the conductivity of electrons. The ultrafine MoP nanoparticles can guarantee high specific capacity and the N, P co-doping could improve wettability of electrodes to electrolytes. As expected, the free-standing MoP@NPCNF electrode demonstrates a high capacity of 320 mAh g-1 at 100 mA g-1 , a superior rate capability maintaining 220 mAh g-1 at 2 A g-1 , as well as a capacity retention of more than 90% even after 200 cycles. The excellent rate performance, high reversible capacity, long-term cycling stability, and facile synthesis routine make this hybrid membrane promising anode for potassium-ion batteries.

Integrated N-Co/Carbon Nanofiber Cathode for Highly Efficient Zinc–Air Batteries

In order to reduce the charge-transfer resistance, ohmic resistance, and ionic and electronic resistances arising from the polymer binder, designing and constructing self-standing and binder-free porous electrodes are very significant for energy storage and conversion devices. Herein, self-standing and binder-free porous N-Co carbon nanofiber (N-Co/CNF) cathodes are prepared for zinc-air batteries (ZABs) by an in situ electrospinning/plasma-etching method. The morphology and activity of the prepared electrodes are investigated by several characterization techniques. The prepared specimens exhibit a multilayered CNF structure, and a new CoN compound is produced after plasma-etching treatment. The N-Co/CNF-300-10 cathode demonstrates excellent electrocatalytic performance toward oxygen reduction reaction, with an onset potential and a half-wave potential of 0.995 and 0.853 V (vs reversible hydrogen electrode), respectively, which is comparable to that of 20% Pt/C. The N-Co/CNF-300-10 cathode acting as a self-standing electrode for ZABs exhibits a maximum discharge power density as high as 229 mW cm-2 and a specific capacity of 659.6 mA h gZn-1, which are much higher than those of the commercial catalysts, benefiting from the self-standing porous structure, N-doping, and more defects and active sites induced by plasma-etching. It provides an effective way to construct a self-standing porous electrode with controllable compositions for rechargeable metal-air batteries.

Characterization and Properties of Cellulose Nanofiber/ Polyaniline Film Composites Synthesized through in Situ Polymerization

Cellulose nanofiber/polyaniline (CNF/PANI) composites films were synthesized through in situ polymerization of aniline in a nanocellulose suspension that was isolated from bamboo (Phyllostachys nidularia Munro). The PANI contents were 5 wt.%, 15 wt.%, or 30 wt.%. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the CNF nanofibril surfaces were uniformly coated by PANI particles. Moreover, Fourier transform infrared (FTIR) spectroscopy analysis indicated the formation of hydrogen bonds between the amine groups of aniline and the hydroxyl groups of cellulose. X-ray diffraction (XRD) analysis demonstrated that the cellulose I structure of CNF in the composites did not change, while the crystallinity of CNF was affected. Thermogravimetric analysis (TGA) showed that the thermal stability of CNF was increased due to the addition of PANI. Meanwhile, the obtained electrical conductivity and mechanical properties of the CNF/PANI composites indicated that the composites could be used potentially in anti-static materials, for shielding of electromagnetic radiation, and in biological sensors.

Development of Carbon Nanofiber Based Non-Precious Metal Catalysts for Oxygen Reduction Reaction

Cost reduction is the most crucial issue in commercialization of polymer electrolyte membrane fuel cells (PEMFCs). According to DOE’s analysis, expensive platinum (Pt) catalyst & its application account for almost half of the PEMFCs stack cost. (500,000 vehicles/year, DOE Annual Merit Review, 2013). For that reason, non-precious metal catalysts (NPMCs) have been extensively developed in recent dates to replace Pt catalyst. Oxygen reduction reaction (ORR) is the main focus in development of NPMCs because of its sluggish reaction kinetics. Previous reports examined that carbon based catalysts, which contain transition metal-nitrogen bond, exhibit high activity, stability, and selectivity for ORR [1-5]. These catalysts are usually synthesized by high temperature pyrolysis of precursor mixture for transition metal (Co or Fe), nitrogen, carbon, and support material. However, it is difficult to prepare uniform mixture using many precursors, and accompanied by complicated synthesis route. Electrospinning is a facile technique to make 1-D structured nanofiber by applying high voltage between viscous polymer solution injection needle and conductive bottom plate. The electrospun nanofiber provides high surface area without support materials. And, polyacyrlronitrile (PAN), which is common precursor for CNF, can act as source for both carbon and nitrogen because PAN has nitrogen containing nitrile group. According to Kim`s doctoral thesis [6], only PAN and cobalt acetate were used for making precursor mixture, and Co-CNF catalysts after the high temperature pyrolysis exhibit high ORR activity comparable with the commercial Pt catalyst in alkaline solution as shown in Fig. 1. However, ORR activity of Co-CNF catalysts is still lower than Pt catalysts even in large amount of catalyst usage, especially in acidic solution. In this study, we were trying to maximize ORR active sites of CNF based catalysts by modification of CNF structure and transition metal composition. To make porous CNF, other polymer materials, such as PMMA, and PVP, were added to electrospinning solution. These polymer materials were evaporated at high temperature pyrolysis, and then remaining CNF has porous structure. The porous CNF exhibit enhanced ORR activity than CNF in alkaline solution by increase in surface area. Heat-treatment under reactive gas, such as NH3, also enables to gain porous structure by gasification of carbon. And, Fe addition in Co-CNF catalysts leads to increase in on-set potential. The Fe,Co-CNF catalysts exhibit same on-set potential with the commercial Pt catalyst as shown in Fig. 3. By optimization of these strategies, we plans to synthesize highly active CNF based NPMCs in alkaline solution and even in acidic solution for future works. Fig. 1 Measured ORR activity of CNF and Co-CNF catalysts in 0.1 M KOH solution. Fig. 2 TEM image of porous CNFFig. 3 Measured ORR activity of Co-CNF and Fe,Co-CNF catalysts in 0.1 M KOH solution. References M. Lefèvre, E. Proietti, F. Jaouen, J.P. Dodelet, Science, 324 (2009) 71-74.R. Bashyam, P. Zelenay, Nature, 443 (2006) 63-66.F. Jaouen, E. Proietti, M. Lefèvre, R. Chenitz, J.P. Dodelet, G. Wu, H.T. Chung, C.M. Johnston, P. Zelenay, Energy and Environmental Science, 4 (2011) 114-130.G. Wu, K. Artyushkova, M. Ferrandon, J. Kropf, D. Myers, P. Zelenay, in, Vienna, 2009, pp. 1299-1311.G. Wu, K.L. More, C.M. Johnston, P. Zelenay, Science, 332 (2011) 443-447M. J. Kim, PhD Degree thesis, KAIST, Republic of Korea, August, 2013.

Insights on the structure of native CNF, an endogenous phospholipase A2 inhibitor from Crotalus durissus terrificus, the South American rattlesnake

Several snake species possess endogenous phospholipase A2 inhibitors (sbPLIs) in their blood plasma, the primary role of which is protection against an eventual presence of toxic phospholipase A2 (PLA2) from their venom glands in the circulation. These inhibitors have an oligomeric structure of, at least, three subunits and have been categorized into three classes (α, β and γ) based on their structural features. SbγPLIs have been further subdivided into two subclasses according to their hetero or homomeric nature, respectively. Despite the considerable number of sbγPLIs described, their structures and mechanisms of action are still not fully understood. In the present study, we focused on the native structure of CNF, a homomeric sbγPLI from Crotalus durissus terrificus, the South American rattlesnake. Based on the results of different biochemical and biophysical experiments, we concluded that, while the native inhibitor occurs as a mixture of oligomers, tetrameric arrangement appears to be the predominant quaternary structure. The inhibitory activity of CNF is most likely associated with this oligomeric conformation. In addition, we suggest that the CNF tetramer has a spherical shape and that tyrosinyl residues could play an important role in the oligomerization. The carbohydrate moiety, which is present in most sbγPLIs, is not essential for the inhibitory activity, oligomerization or complex formation of the CNF with the target PLA2. A minor component, comprising no more than 16% of the sample, was identified in the CNF preparations. The amino-terminal sequence of that component is similar to the B subunits of the heteromeric sbγPLIs; however, the role played by such molecule in the functionality of the CNF, if any, remains to be determined.

Facile synthesis of open mesoporous carbon nanofibers with tailored nanostructure as a highly efficient counter electrode in CdSe quantum-dot-sensitized solar cells

A simple but very efficient reproducible approach was developed to fabricate novel mesoporous carbon nanofibers (MCNFs) with tailored nanostructure by using porous anodic aluminium oxide (AAO) membrane and colloidal silica as hard templates and phenolic resin as a carbon source. The as-prepared MCNFs with a channel diameter of ca. 200 nm reveal uniform one-dimensional (1D) nanofiber structure, created by the replication of the AAO template, and open interconnected spherical mesopores of ca. 30 nm in diameter embedded in the CNFs, mainly controlled by the particle size of the silica template. Due to their large mesopore size and volume, high specific surface area and unique nanostructure constituted by the 1D macro-scaled porous CNF and 3D interconnected mesopore structure, the MCNFs not only possess a large electrochemically active surface area, but also an open highway network favoring rapid electron transfer and fast mass transport. As a counter electrode in a CdSe quantum-dot-sensitized solar cell, the MCNF has demonstrated higher catalytic activity towards the reduction of polysulfide electrolyte and superior photovoltaic performance to its peers such as activated carbon (AC), hollow core/mesoporous shell carbon and ordered multimodal porous carbon, and the commonly used Pt electrode, revealing a fill factor of 0.60 and a power conversion efficiency of up to 4.81%. Excellent photovoltaic performance demonstrated by the MCNF suggests synergetic effects from the combination of 1D and 3D nanostructures.

Highly sensitive amperometric biosensors for phenols based on polyaniline–ionic liquid–carbon nanofiber composite

A novel polyaniline–ionic liquid–carbon nanofiber (PANI–IL–CNF) composite was greenly prepared by in situ one-step electropolymerization of aniline in the presence of IL and CNF for fabrication of amperometric biosensors. The scanning electron micrographs confirmed that the PANI uniformly grew along with the structure of CNF and the PANI–IL–CNF composite film showed a fibrillar morphology with the diameter of around 95nm. A phenol biosensor was constructed by immobilizing tyrosinase on the surface of the composite modified glassy carbon electrode via the cross-linking step with glutaraldehyde. The biosensor exhibited a wide linear response to catechol ranging from 4.0×10−10 to 2.1×10−6M with a high sensitivity of 296±4AM−1cm−2, a limit of detection down to 0.1nM at the signal to noise ratio of 3 and applied potential of −0.05V. According to the Arrhenius equation, the activation energy for enzymatic reaction was calculated to be 38.8kJmol−1 using catechol as the substrate. The apparent Michaelis–Menten constants of the enzyme electrode were estimated to be 1.44, 1.33, 1.16, 0.65μM for catechol, p-cresol, phenol, m-cresol, respectively. The functionalization of CNF with PANI in IL provided good biocompatible platform for biosensing and biocatalysis.

The Bimetallic Effects of Catalysts on the Syntheses of Thin Carbon Nanofibers

Thin carbon nanofibers with less than 100 nm diameter were variously prepared over MgO-supported nickel and bimetallic nickel catalysts with iron, copper, and molybdenum. The second metal effects on the carbon yield and structure were investigated by using electron microscopic and gas chromatographic methods. Further, the active catalysts were examined by powdered X-ray diffraction to elucidate correlation between the catalyst and nanofiber growth. The surface composition of catalysts appeared to govern the catalyst activity and the resulting CNF structure. The second metal effects on the catalyst activity and resulting nanofiber structure is discussed in terms of the formation mechanism of carbon nanofibers, on the basis of the results.