Carbon Nanofiber Membranes Research Articles

A two-pronged strategy to boost the capacitive deionization performance of nitrogen-doped porous carbon nanofiber membranes

Carbon-based capacitive deionization (CDI) systems are universally subject to the limited desalination capacity, due to the electrosorption characteristics and undesirable pore structures. Herein, a two-pronged strategy is proposed to boost the desalination performance of the electrospun carbon nanofibers (CNFs), where silicalite-1 nanoparticles as the internal porogen create mesopores and macropores, and zeolitic imidazolate framework (ZIF-L) leaves as the external carbon source provide micropores and mesopores. This combination results in the large surface area, well-developed graded pore structure, and increased nitrogen content of the core-shell polyacrylonitrile/silicalite-1@ZIF-L-derived CNFs (defined as PCNFs-SZ) electrode, which delivers a superior specific capacitance of 145.4 F g−1 in a neutral electrolyte. The symmetric CDI cell assembled by the self-supporting PCNFs-SZ membrane electrodes holds a prominent desalination capacity of 37.09 mg g−1 and a rapid salt removal rate of 10.36 mg g−1 min−1 at 1.2 V (initial NaCl concentration: 500 mg L−1), and demonstrates significant potential for real-world applications in the desalination and purification of reclaimed water. Furthermore, theory calculations confirm the enhanced Na+-capture capability of PCNFs-SZ. The present work highlights an effective and viable approach to enhance the desalination performance of carbon-based CDI cells.

Superhydrophilic and porous carbon nanofiber membrane for high performance solar-driven interfacial evaporator

In light of the mounting global water crisis, solar interfacial evaporation has emerged as a pivotal technology for the advancement of water resource management. One of the most effective methods for enhancing the evaporation rate of solar evaporators is to optimize their utilization of light. In this study, a superhydrophilic Cu/C porous fiber evaporator was prepared using a multi-fluid electrospinning technology and a thermal treatment method. This evaporator exhibits excellent evaporation performance under the effect of Cu NPs, carbon fiber and a porous structure. The results demonstrated that the evaporation rate of the evaporator could reach 1.41 kg m−2 h−1 under one sunlight irradiation (Evaporation efficiency of 94.6 %). In addition, for wastewater containing organic dyes, acidic and alkaline, the evaporator has a significant cleaning effect. This high photothermal conversion efficiency suggests a promising avenue for the utilization of solar energy in water purification.

Two birds with one stone: Bimetallic ZnCo2S4 polyhedral nanoparticles decorated porous N-doped carbon nanofiber membranes for free-standing flexible anodes and microwave absorption

Cost-efficient material with an ingenious design is important in the engineering applications of flexible energy storage and electromagnetic (EM) protection. In this study, bimetallic ZnCo2S4 (ZCS) polyhedral nanoparticles homogenously embedded in the surface of porous N-doped carbon nanofiber membranes (ZCS@PCNFM) have been fabricated by electrospinning technique combined with carbonization and hydrothermal processes. As a self-assembled electrode for lithium-ion batteries (LIBs), the bimetallic ZCS nanoparticles possess rich redox reactions, good electrical conductivity, and pseudocapacitive properties, while the three-dimensional (3D) multiaperture architecture of the nanofiber film not only shortens the transfer spacing of lithium ions and electrons but also effectively tolerates the volume variation during lithiation and delithiation cycles. Benefiting from the above merits, the ZCS@PCNFM electrode exhibits good cycle performance (662.3 mA h/g at 100 mA/g after 100 cycles), superior rate capacity (401.3 mA h/g at 1 A/g) and an extremely high initial specific capacity of 1152.2 mAh/g at 100 mA/g. Meanwhile, depending on the hierarchical nanostructure and multi-component heterogeneous interface effects constructed by 3D inlaid architecture, the ZCS@PCNFM nanocomposite exhibits fascinating microwave absorption (MA) characteristics with a superhigh reflection loss (RL) of –49.7 dB at a filling content of only 20 wt% and corresponding effective absorption bandwidth (EAB, RL<–10 dB) of 5.2 GHz ranging from 12.8 to 18.0 GHz at 2.2 mm.

Controllable preparation of carbon nanofiber membranes for enhanced flexibility and permeability

The electrospinning-produced carbon nanofiber membranes (CNFM) have been applied in many fields for their three-dimensional porous networks, however, the natural fragility impedes their practical applications. Introducing plasticizers into carbon fibers has been proven an efficient way to increase the flexibility of CNFM but the extent is limited. This work explored dual plasticizers strategy to improve the flexibility of CNFM. The addition of zinc acetate and tetraethyl orthosilicate leads to bigger carbon nanofibers and higher mean pore diameters. They can be transformed into SiO2 and ZnO nanoparticles that embed in the carbon fibers, and act as plasticizers to inhibit stress diffusion. The Young's modulus of the optimal SZCNFM-2.0-1.5-700 is 31.0 MPa, which is lower than single plasticizer can reduce. The mechanism of dual plasticizers collaboratively improving the flexibility of SZCNFM was proved based on the characterization results. The SZCNFM-2.0-1.5-700 with well flexibility also revealed high permeability, for instance, the gravity-induced cyclohexane flux is 486.67 L m−2 h−1. Furthermore, the SZCNFM-2.0-1.5-700 requires only half the time compared to the commercial filter membrane when separating the same amount of Pd@CN suspension in the suction filter.

Highly Efficient One-pot Electrosynthesis of Oxime Ethers from NOx over Ultrafine MgO Nanoparticles Derived from Mg-based Metal-Organic Frameworks.

Oxime ethers are attractive compounds in medicinal scaffolds due to the biological and pharmaceutical properties, however, the crucial and widespread step of industrial oxime formation using explosive hydroxylamine (NH2OH) is insecure and troublesome. Herein, we present a convenient method of oxime ether synthesis in a one-pot tandem electrochemical system using magnesium based metal-organic framework-derived magnesium oxide anchoring in self-supporting carbon nanofiber membrane catalyst (MgO-SCM), the in situ produced NH2OH from nitrogen oxides electrocatalytic reduction coupled with aldehyde to produce 4-cyanobenzaldoxime with a selectivity of 93 % and Faraday efficiency up to 65.1 %, which further reacted with benzyl bromide to directly give oxime ether precipitate with a purity of 97 % by convenient filtering separation. The high efficiency was attributed to the ultrafine MgO nanoparticles in MgO-SCM, effectively inhibiting hydrogen evolution reaction and accelerating the production of NH2OH, which rapidly attacked carbonyl of aldehydes to form oximes, but hardly crossed the hydrogenation barrier of forming amines, thus leading to a high yield of oxime ether when coupling benzyl bromide nucleophilic reaction. This work highlights the importance of kinetic control in complex electrosynthetic organonitrogen system and demonstrates a green and safe alternative method for synthesis of organic nitrogen drug molecules.

Highly Efficient One‐pot Electrosynthesis of Oxime Ethers from NOx over Ultrafine MgO Nanoparticles Derived from Mg‐based Metal‐Organic Frameworks

AbstractOxime ethers are attractive compounds in medicinal scaffolds due to the biological and pharmaceutical properties, however, the crucial and widespread step of industrial oxime formation using explosive hydroxylamine (NH2OH) is insecure and troublesome. Herein, we present a convenient method of oxime ether synthesis in a one‐pot tandem electrochemical system using magnesium based metal‐organic framework‐derived magnesium oxide anchoring in self‐supporting carbon nanofiber membrane catalyst (MgO‐SCM), the in situ produced NH2OH from nitrogen oxides electrocatalytic reduction coupled with aldehyde to produce 4‐cyanobenzaldoxime with a selectivity of 93 % and Faraday efficiency up to 65.1 %, which further reacted with benzyl bromide to directly give oxime ether precipitate with a purity of 97 % by convenient filtering separation. The high efficiency was attributed to the ultrafine MgO nanoparticles in MgO‐SCM, effectively inhibiting hydrogen evolution reaction and accelerating the production of NH2OH, which rapidly attacked carbonyl of aldehydes to form oximes, but hardly crossed the hydrogenation barrier of forming amines, thus leading to a high yield of oxime ether when coupling benzyl bromide nucleophilic reaction. This work highlights the importance of kinetic control in complex electrosynthetic organonitrogen system and demonstrates a green and safe alternative method for synthesis of organic nitrogen drug molecules.

Carbon Nanofiber Membranes Loaded with MXene@g-C3N4: Preparation and Photocatalytic Property

In this study, a Ti3C2 MXene@g-C3N4 composite powder (TM-CN) was prepared by the ultrasonic self-assembly method and then loaded onto a carbon nanofiber membrane by the self-assembly properties of MXene for the treatment of organic pollutants in wastewater. The characterization of the TM-CN and the C-TM-CN was conducted via X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectrometer (FTIR) to ascertain the successful modification. The organic dye degradation experiments demonstrated that introducing an appropriate amount of Ti3C2 MXene resulted in the complete degradation of RhB within 60 min, three times the photocatalytic efficiency of a pure g-C3N4. The C-TM-CN exhibited the stable and outstanding photocatalytic degradation of the RhB solution over a wide range of pH values, indicating the characteristics of the photodegradation of organic pollutants in a wide range of aqueous environments. Furthermore, the results of the cyclic degradation experiments demonstrated that the C-TM-CN composite film maintained a degradation efficiency of over 85% after five cycles, thereby confirming a notable improvement in its cyclic stability. Consequently, the C-TM-CN composite film exhibits excellent photocatalytic performance and is readily recyclable, making it an auspicious eco-friendly material in water environment remediation.

Copper Nanoparticles Modified Superhydrophobic Electrospun Carbon Nanofiber Membranes with Enhanced the Oil–water Separation Performance

Copper Nanoparticles Modified Superhydrophobic Electrospun Carbon Nanofiber Membranes with Enhanced the Oil–water Separation Performance

Resistance‐type strain sensor based on carbon nanofiber/polypyrrole composite membrane with high sensitivity

AbstractCarbon nanofibers have been widely studied as one of the promising materials for fabricating flexible electronic strain sensors. Surface modification of carbon nanofibers by conducting polymers is a simple yet effective approach to constructing strain sensors with good conductivity and sensitivity. In this work, composite nanofiber membranes composed of carbon nanofiber and conducting polymer are developed via in situ polymerization of pyrrole, aniline, and thiophene respectively on the surface of the carbon nanofiber which serves as a substrate. Different composite membranes, CNF@PANI, CNF/Ppy, and CNF@PTh, are successfully manufactured. The conducting polymer‐carbon nanofiber composite membranes exhibit improved conductivity as well as response sensitivity compared to pristine carbon nanofiber membranes. Among different composite membranes being studied, CNF/Ppy demonstrates the highest strain‐sensing performance. It shows good sensitivity, reproducibility, and stability in detecting both subtle (strain = 0.1%) and large (strain = 25%) deformation. The excellent strain‐sensing performance of CNF/Ppy endows the composite membrane with great potential for applications in wearable electronics.Highlights Adding PANI, Ppy, and PTh could improve the conductivity of the CNF sensor. Ppy doping has a good effect on the performance of the CNF strain sensor. CNF/Ppy strain sensor has high sensitivity, stability, and durability. CNF/Ppy sensors can detect deformation caused by human movement. CP‐CNF composite material has good flexibility and mechanical properties.

Flexible and crosslinking electrospun porous carbon nanofiber membranes as freestanding binder-free anodes for lithium-ion batteries

Electrospinning carbon nanofibers with one-dimensional nanostructures have enormous potential for electronic applications owing to their flexibility, electrical conductivity, high surface area and attractive structure. In this paper, porous nitrogen-doped carbon nanofiber membranes with chemical crosslinking structure (PNCNMs-CC) were prepared for lithium-ion batteries anodes by crosslinking treatment and carbonization process using polyimide as precursor, melamine as nitrogen source and ethyl orthosilicate as pore-forming agent. The heightened nitrogen content synergizes with the augmented specific surface area, engendering a striking electrochemical enhancement. Rich pore structure provides more active sites. When utilized as a binder-free, current collector-free anode, PNCNMs-CC shows an excellent rate performance and long cycle stability. The first discharge specific capacity of PNCNMs-CC delivered 710 mAh g−1 at 50 mA g−1. After 1000 cycles at a high current density of 1 A g−1, PNCNMs-CC shows 88 % capacity retention, demonstrating a promising candidate as the flexible anodes for high-performance energy storage devices.

Advanced Lithium-sulfur batteries enabled by a flexible electrocatalytic membrane of TiO2 and SiO2 co-decorated necklace-like carbon nanofibers

Lithium-sulfur (Li-S) batteries are regarded as new energy storage systems due to their low cost and high specific energy density; however, their commercial prospects are hindered by the shuttle effect of lithium polysulfides (LiPSs). Herein, the fabricating necklace-like carbon nanofibers membrane co-decorated by TiO2 and SiO2 (TiO2@SiO2/CNF) is prepared by the electrospinning technique as an interlayer to catalyze the conversion of LiPSs in Li-S batteries. The necklace-like nanofibers provide a three-dimensional conductive network, enabling SiO2 synergy with TiO2 to accelerate the redox kinetics of LiPSs through an enhanced interfacial effect. The Li-S batteries based on TiO2@SiO2/CNF interlayers exhibit an impressive specific capacity of 658 mAh g−1 at 3.0C, and their performances are decayed only 0.05 % per cycle at 1.0C within 500cycles. Our study reveals that the shuttle effect addition of LiPSs can be significantly improved by rational structural design, thus enhancing the electrochemical performance of Li-S batteries. The synthesis of necklace-like TiO2@SiO2/CNF presents a promising strategy for designing functional interlayers for advanced Li-S batteries.

Enhanced electrocatalytic degradation of tetracycline by ZIF-67@CNT coupled with a self-standing aligned carbon nanofiber anodic membrane

Due to the misuse and overuse of the antibiotic tetracycline (TC), as well as its refractory degradability, it has become a stubborn environmental contaminant. In this study, a self-standing polyacrylonitrile-based ZIF-67@CNT/ACF aligned anodic membrane was fabricated by innovatively incorporating ZIF-67@CNT nanoparticles into an aligned carbon nanofiber (ACF) membrane to treat the TC. The flow-through nanoporous construction of the ZIF-67@CNT/ACF membrane reactor can compress the diffusion boundary layer on the electrode surface to enhance mass transfer under microscopic laminar flow, which can further enhance the degradation rate. In addition, the enhanced degradation performance also benefited from the significant electrooxidation capacity of the ZIF-67@CNT/ACF membrane. At the optimal electrocatalytic condition of 3.0 V applied potential and pH 6, the degradation rate reached 81% in 1 h for an initial TC concentration of 10 mg l−1. The refractory and highly toxic TC was electrochemically degraded into small non-toxic molecules. Our results indicate that electrocatalytic TC degradation can be enhanced by ZIF-67@CNT/ACF membrane.

Preparation and characterization of palladium nanoparticle-embedded carbon nanofiber membranes via electrospinning and carbonization strategy.

Carbon nanofiber membranes (CNMs) are expected to be used in many energy devices to improve the reaction rate. In this paper, CNMs embedded with palladium nanoparticles (Pd-CNMs) were prepared by electrospinning and carbonization using polyimide as the raw material. The effects of carbonization temperature, carbonization atmosphere, and heating rate on the physicochemical properties of the as-obtained Pd-CNMs were studied in detail. On this basis, the electrocatalytic performance of Pd-CNMs prepared under optimal conditions was characterized. The results showed that highly active zero-valent palladium nanoparticles with uniform particle size could be distributed on the surface of carbon nanofibers. Under vacuum conditions, at a carbonization temperature of 800 °C and a heating rate of 2 °C min-1, Pd-CNMs have lower H2O2 yield, lower Tafel slope (73.3 mV dec-1), higher electron transfer number (∼4), and superior durability, suggesting that Pd-CNMs exhibit excellent electrocatalytic activity for ORR in alkaline electrolyte. Therefore, polyimide-derived CNMs embedded with Pd nanoparticles are expected to become an excellent cathode catalyst layer for fuel cells.

Well-dispersed FeNi nanoparticles embedded in N-doped carbon nanofiber membrane as a self-supporting and binder-free anode for lithium-ion batteries

The as-prepared flexible FeNi@NCNF is directly utilized as an electrode in LIBs without the use of any binders or conductive additives and exhibits superior electrochemical performance.

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

Stabilizing iron single atoms with electrospun hollow carbon nanofibers as self-standing air-electrodes for long-time Zn − air batteries

Developing iron-based single-atom catalysts (Fe SACs) with low cost, high activity and stability is vital for commercialising sustainable energy technologies. However, accurately controlling and identifying structure–activity relationships of Fe SACs remains a significant challenge. Herein, we report Fe/N co-doped carbon nanofiber membranes with highly exposed Fe-N4 sites (Fe/NCNFs), synthesized by electrospinning and pyrolysis. The three-dimensional (3D) hierarchical structure and atomically dispersed pyrrole-type Fe (III)-N4 active sites provide the as-prepared catalyst with a positive half-wave potential of 0.87 V and an ultralow Tafel slope of 53 mV dec−1. As an air cathode catalyst for liquid Zn − air batteries, it delivers a high open-circuit voltage (1.474 V), a large peak power density (190 mW cm−2) and a high durability of 2000 cycles at 5 mA cm−2. As a self-standing air cathode, the as-assembled solid-state Zn − air batteries also show stable cycling with a small discharge/charge voltage gap of 0.65 V, indicating great prospects for developing portable zinc − air batteries.

Using Highly Flexible SbSn@NC Nanofibers as Binderless Anodes for Sodium-Ion Batteries

Flexible and binderless electrodes have become a promising candidate for the next generation of flexible power storage devices. However, developing high-performance electrode materials with high energy density and a long cycle life remains a serious challenge for sodium-ion batteries (SIBs). The main issue is the large volume change in electrode materials during the cycling processes, leading to rapid capacity decay for SIBs. In this study, flexible electrodes for a SnSb alloy–carbon nanofiber (SnSb@NC) membrane were successfully synthesized with the aid of hydrothermal, electrospinning and annealing processes. The as-prepared binderless SnSb@NC flexible anodes were investigated for the storage properties of SIBs at 500 °C, 600 °C and 700 °C (SnSb@NC-500, SnSb@NC-600 and SnSb@NC-700), respectively. And the flexible SnSb@NC-700 electrode displayed the preferable SIB performances, achieving 240 mAh/g after 100 cycles at 0.1 A g−1. In degree-dependent I-V curve measurements, the SnSb@NC-700 membrane exhibited almost the same current at different bending degrees of 0°, 45°, 90°, 120° and 175°, indicating the outstanding mechanical properties of the flexible binderless electrodes.

Graphene sheets assembled into three-dimensional networks of carbon nanofibers: A nano-engineering approach for binder-free supercapacitor electrodes

The design and synthesis of flexible and free-standing carbon nanofibers membrane with good electrochemical properties have recently attracted much attention in energy storage applications. Herein, we fabricated graphene sheets-incorporated three-dimensional carbon nanofibers membrane (3D-GCNFs) as effective electrode materials for supercapacitors. The electrospun two-dimensional (2D) graphene oxide sheets-incorporated polyacrylonitrile nanofibers (GO/PAN NFs) were transformed into 3D membrane by a gas-forming technique using sodium borohydride. Subsequent thermal treatment converted the 2D-assembled GO/PAN NFs membrane into the low-density 3D-GCNFs membrane. The morphology and electrochemical performances of the as-prepared 3D membrane were systematically investigated using state-of-the-art techniques. It was found that the electrochemical performance of the as-obtained 3D-GCNFs membrane was greatly improved compared to the 2D counterparts. As a binder-free electrode, the materials exhibited a high areal capacitance of 318 mF/cm2 at a current density of 1 mA/cm2 and good cyclic stability of up to 98.5% after 5000 cycles. In addition, a symmetrical supercapacitor was constructed using the 3D-GCNFs membrane as both negative and positive electrodes. The device exhibited areal capacitance of 240 mF/cm2 at a current density of 1 mA/cm2, an energy density of 33.33 mWh/cm2, a power density of 1000 mW/cm2, and capacitance retention of 103% after 5000 cycles. The improved performance of the 3D-GCNFs membrane was attributed to its high electrical conductivity due to the absence of binders, high porosity, and conductive networks that form efficient channels for electrolyte penetration and effectively shorten the transmission distance. We believe that this study not only provides a reference for the introduction of 3D CNFs-based composite membranes, but also demonstrates their great potential for energy storage applications.

Freestanding hybrid electrospun membranes consisting of TiO2 nanotube-core nanocarbon as high-performance and long-lifespan anodes for lithium-ion batteries

To develop an efficient anode for lithium ion batteries (LIBs), we prepare an ultralong oxygen-deficient titanium dioxide nanotubes (TNTs)-based hybrid electrospun carbon nanofibers (CNFs) membrane (TNT@CNFs). As an anode, this membrane possesses several advantages, including fast ion/electron transport path due to the TNTs’ novel structure, protection from direct contact between TNTs and electrolyte owing to the carbon skeleton, improved electrical conductivity on account of the internal structural consistency of TNTs, and enhanced ion transport because of oxygen vacancies. As a result, the anode with a relatively low content of TNT (33TNT@CNFs) exhibits an ultra-high reversible specific capacity of 350 mAh/g after 200 cycles at a relatively low current density (0.2 A/g), while the anode with a high content of TNT (50TNT@CNFs) exhibits an ultra-high rate performance of 187 mAh/g at 10 A/g after 10,000 cycles, indicating its superior electrochemical kinetics at high-rate and long cyclic lifespan. This can find proof from the dynamic analysis that both the surface capacitance process and the diffusion-controlled insertion have a great contribution. The strategy employed in this work can facilitate access to a variety of one-dimensional (1D) nanostructured composites and can promote new research on electrodes for ultrafast rechargeable LIBs.

Flexible CoFe2O4 nanoparticles/N-doped carbon nanofibers membrane as self-standing anode for lithium-ion batteries

The development of new generation wearable electronic devices requires the power supply with high power density, long-term cycling performance, and excellent flexibility and mechanical stability that would enhance the durability of flexible devices during use. Herein, we designed a novel strategy for the preparation of flexible self-supporting nanofiber membrane with highly dispersed CoFe2O4 nanoparticles embedded in one-dimensional (1D) N-doped carbon nanofibers (denoted as [email protected]) by electrospinning and subsequent thermal treatment process, which possesses unique hierarchical structure containing zero-dimensional [email protected] carbon nanospheres and cross-linked three-dimensional (3D) fiber network. The rational combination of the nano-sized CFO particles with high theoretical capacity and a N-doped carbon nanofiber conductive skeleton with interconnected 3D open microstructure facilitates the robust penetration of electrolyte into the electrode, improves the overall electrical conductivity of the electrode, shortens the diffusion pathways of Li+ ions, and buffers the volume change of active materials during lithiation/delithiation. As a consequence, the optimized [email protected] exhibits relatively high electrochemical reversible capacity (611.4 mA h g−1 at 100 mA g−1 after 100 cycles) and good cycling stability, as well as satisfactory rate capability.