Mesoporous Carbon Nanofibers Loaded with Ordered PtFe Alloy Nanoparticles for Electrocatalytic Nitrate Reduction to Ammonia

Highly dispersed bimetallic alloy nanoparticle electrocatalysts have been demonstrated to exhibit exceptional performance in driving the nitrate reduction reaction(NO_(3)RR)to generate ammonia(NH_(3)).In this study,we prepared mesoporous carbon nanofibers(mCNFs)functionalized with ordered PtFe alloys(O-PtFe-mCNFs)by a composite micelle interface-induced co-assembly method using poly(ethylene oxide)-block-polystyrene(PEO-b-PS)as a template.When employed as electrocatalysts,O-PtFe-mCNFs exhibited superior electrocatalytic performance for the NO_(3RR)compared to the mCNFs functionalized with disordered PtFe alloys(D-PtFe-mCNFs).Notably,the NH_(3)production performance was particularly outstanding,with a maximum NH_(3)yield of up to 959.6μmol/(h·cm~2).Furthermore,the Faraday efficiency(FE)was even 88.0%at-0.4 V vs.reversible hydrogen electrode(RHE).This finding provides compelling evidence of the potential of ordered PtFe alloy catalysts for the electrocatalytic NO_(3)RR.

锂硫电池中CNTs-CNFs夹层对多硫化物的捕获和加速转化机理

为有效抑制多硫化锂(LiPSs)的穿梭效应,通过静电纺丝、电化学沉积和化学气相生长技术在碳纳米纤维(CNFs)上垂直生长碳纳米管(CNTs),开发了一种超薄、轻质的多功能三维多层交联碳纳米纤维-碳纳米管(CNTs-CNFs)夹层,并研究CNTs-CNFs对锂硫电池(LSBs)电化学性能的影响。研究结果表明:CNTs-CNFs薄膜优异的导电性和丰富的孔隙结构为LSBs提供了均匀的导电网络和LiPSs的吸附过滤屏障,与无夹层相比,含有CNTs-CNFs夹层的电池具有更优异的容量保持率和循环稳定性,在0.2 C电流密度下具有1296.7 mA·h/g的初始放电比容量,在100次循环后仍能提供了864.7 mA·h/g的放电比容量,容量保持率为66.68%。

细菌纤维素基CNFs/ZnO吸波材料的制备及性能

随着电子信息技术的不断发展,电磁污染问题日益严重,高效吸波材料的研究受到越来越多的关注。该文以生物多孔材料细菌纤维素为碳源,采用碳化改性和水热法两步制备了细菌纤维素基CNFs/ZnO复合材料,研究了二水合醋酸锌的浓度对CNFs/ZnO复合材料吸波性能的影响。通过X射线衍射仪(XRD)、冷场发射扫描电子显微镜(FESEM)、矢量网络分析仪(VNA)对复合材料的结构、形貌和吸波性能进行表征。结果表明:CNFs/ZnO复合材料被成功制备,其中碳纳米纤维(CNFs)没有明显的衍射峰,呈无定形状态;碳化和改性CNFs均保持了细菌纤维素三维网络多孔架构的精细纳米纤维微观形貌,但是CNFs变得卷曲且直径明显减小;CNFs/ZnO复合材料中,ZnO被紧密吸引在CNFs表面或随机插入CNFs的空隙中。通过改变二水合醋酸锌的浓度可以控制ZnO在复合材料中的含量,进而调控复合材料的电磁参数,获得良好的阻抗匹配。当二水合醋酸锌的浓度为0.25 mol/L时,ZnO在CNFs上分散得最为均匀,此时CNFs和ZnO的电阻损耗、介电损耗和界面极化等协同作用于三维多孔网络结构上,增加了复合材料对电磁波的多次反射、散射和长程耗散作用。该条件下制备的CNFs/ZnO复合材料,在涂层厚度为2.8 mm、频率为15.1 GHz附近时,其最佳反射损耗为−57.5 dB,有效吸收带宽为7.1 GHz,是一种可靠的复合吸波材料。

Integration of Desulfurization and Lithium-Sulfur Batteries Enabled by Amino-Functionalized Porous Carbon Nanofibers

Hydrogen sulfide(H_(2)S)is an industrial exhausted gas that is highly toxic to humans and the environment.Combining desulfurization and fabrication of cathode materials for lithium-sulfur batteries(LSBs)can solve this issue with a double benefit.Herein,the amino-functionalized lotus root-like carbon nanofibers(NH_(2)-PLCNFs)are prepared by the amination of electrospinning carbon nanofibers under dielectric barrier discharge plasma.Selective catalytic oxidation of H_(2)S to elemental sulfur(S)is achieved over the metalfree NH_(2)-PLCNFs catalyst,and the obtained composite S@NH_(2)-PLCNFs is further used as cathode in LSBs.NH_(2)-PLCNFs enable efficient desulfurization(removal capacity as high as 3.46 g H_(2)S g^(−1) catalyst)and strongly covalent stabilization of S on modified carbon nanofibers.LSBs equipped with S@NH_(2)-PLCNFs deliver a high specific capacity of 705.8 mA h g^(−1) at 1 C after 1000 cycles based on the spatial confinement and the covalent stabilization of electroactive materials on amino-functionalized porous carbon matrix.It is revealed that S@NH_(2)-PLCNFs obtained by this kind of chemical vapor deposition leads to a more homogeneous S distribution and superior electrochemical performance to the sample S/NH_(2)-PLCNF-M prepared by the traditional molten infusion.This work opens a new avenue for the combination of environment protection and energy storage.

PtZn nanoparticles supported on porous nitrogen-doped carbon nanofibers as highly stable electrocatalysts for oxygen reduction reaction

The oxygen reduction reaction(ORR)electrocatalytic activity of Pt-based catalysts can be significantly improved by supporting Pt and its alloy nanoparticles(NPs)on a porous carbon support with large surface area.However,such catalysts are often obtained by constructing porous carbon support followed by depositing Pt and its alloy NPs inside the pores,in which the migration and agglomeration of Pt NPs are inevitable under harsh operating conditions owing to the relatively weak interaction between NPs and carbon support.Here we develop a facile electrospinning strategy to in-situ prepare small-sized PtZn NPs supported on porous nitrogen-doped carbon nanofibers.Electrochemical results demonstrate that the as-prepared PtZn alloy catalyst exhibits excellent initial ORR activity with a half-wave potential(E_(1/2))of 0.911 V versus reversible hydrogen electrode(vs.RHE)and enhanced durability with only decreasing 11 mV after 30,000 potential cycles,compared to a more significant drop of 24 mV in E_(1/2)of Pt/C catalysts(after 10,000 potential cycling).Such a desirable performance is ascribed to the created triple-phase reaction boundary assisted by the evaporation of Zn and strengthened interaction between nanoparticles and the carbon support,inhibiting the migration and aggregation of NPs during the ORR.

Chemically activated carbon nanofibers for adsorptive removal of bisphenol-A:Batch adsorption and breakthrough curve study

Activated carbon nanofibers(ACNFs)with small diameter can significantly increase the accessibility of intra pores and accelerate adsorption of molecules from water.In this study,ACNFs were made by blending K_(2)CO_(3)or ZnCl_(2)as the activating agent into the polyacrylonitrile(PAN)in dimethylformamide solution for electrospinning prior to pyrolysis.Bisphenol-A(BPA),an endocrine disruption pollutant,is widely applied in the production of polycarbonate plastics and epoxy resins.Accordingly,BPA is often used as a model contaminant commonly removed via adsorption.Batch adsorption studies were used to evaluate the kinetics and adsorption capacity of the ACNFs.Redlich-Peterson(R-P)and Langmuir models were found to fit the isotherm of BPA adsorption better than Freundlich model,showing the homogeneous nature of the PAN originated ACNFs.The adsorption kinetics was better described by the pseudo second-order model than that by the pseudo first-order model.The fitting by intraparticle diffusion model indicates the adsorption of BPA onto ACNFs is mainly controlled by pore diffusion.High pH value and ionic strength reduced BPA adsorption from aqueous solution.The breakthrough curves studied in two different fixed bed systems(cross flow bed system and packed flow bed system)confirmed the scalability of BPA removal by ACNFs in dynamic adsorption processes.The modified dose-response model predicted well the fixed-bed outlet concentration profiles.

3D Free-Standing Carbon Nanofibers Modified by Lithiophilic Metals Enabling Dendrite-Free Anodes for Li Metal Batteries

Li metal with high-energy density is considered as the most promising anode for the next-generation rechargeable Li metal batteries;however,the growth of Li dendrites seriously hinders its practical application.Herein,3D free-standing carbon nanofibers modified by lithiophilic metal particles(CNF/Me,Me=Sn,Fe,Co)are obtained in situ by the electrospinning method.Benefiting from the lithophilicity,the CNF/Me composite may effectively prevent the formation of Li dendrites in the Li metal batteries.The optimized CNF/Sn–Li composite electrode exhibits a stable cycle life of over 2350 h during Li plating/stripping.When matched with typical commercial LiFePO_(4)(LFP)cathode,the LFP//CNF/Sn–Li full cell presents a high initial discharge specific capacity of 139 mAh g^(−1)at 1 C,which remains at 146 mAh g^(−1)after 400 cycles.When another state-of-the-art commercial LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM(811))cathode is used,the assembled NCM//CNF/Sn–Li full cell shows a large initial specific discharge capacity of 206 mAh g^(−1)at substantially enhanced 10 C,which keeps at the good capacity of 99 mAh g^(−1)after 300 cycles.These results are greatly superior to the counterparts with Li as the anodes,indicating the great potential for practical utilization of the advanced CNF/Sn–Li electrode.

静电纺丝法制备自支撑Zn_(2)VO_(4)/N-CNFs复合中间层及电化学性能研究

应用静电纺丝技术设计了一种具有3D网状结构的Zn、V双金属化合物-氮掺杂碳纳米纤维自支撑中间层(Zn_(2)VO_(4)4/N-CNFs),被用于锂硫电池。结果表明,吡啶氮和吡咯氮能与锂离子发生强的相互作用,Zn_(2)VO_(4)4对多硫化锂有极强的吸附和催化效果。碳纳米纤维网络捕捉多硫化锂的同时还可以提供长程电子传导路径,在促进电子转移的同时又能存储电解液,提供了电化学反应空间。Zn_(2)VO_(4)4/N-CNFs中间层发挥了对多硫化锂从捕捉到促进转化的双功能作用。因此,采用Zn_(2)VO_(4)4/N-CNFs中间层的锂硫电池在0.2 C下的初始放电比容量为796.1 mAh·g^(-1),循环100圈后仍可保持727.2 mAh·g^(-1)的容量,容量保持率为91.3%。在1.0 C时,电池的初始容量为593.4 mAh·g^(-1),循环1000圈后仍保有353.3 mAh·g^(-1)的容量,每圈的容量衰减仅为0.0024%。

CVD参数对镀镍碳纤维原位生长CNFs形貌的影响及生长机理分析

碳纤维具有低密度、高模量及高力学强度等优势,是常见的复合材料增强体。通过表面改性的方式,实现碳纤维表面纳米碳材料的有效复合,可获得更优的材料性能。而目前常见的制备方法,可能存在催化剂引入过程损伤纤维、反应时间长等缺点。因此,探索工业化大规模负载纳米尺度碳材料的制备工艺十分必要。采用商用镀镍碳纤维为原料,通过调节化学气相沉积法(CVD)参数,实现不同形貌碳纳米纤维(CNFs)在镀镍碳纤维表面的有效负载,通过SEM、EDS和TEM等表征方式,结合扩散理论和V-S-L模型,分析催化剂厚度对催化剂形态的影响及CVD参数对各形貌产物的影响机理。结果表明,当催化剂层较厚时,催化剂以连续的片状形态存在,主要控制因素为热失配而非表面张力。H_(2)比例较高时,反应以扩散为主导,形貌趋向于催化剂位于中间的粗大CNFs阵列;H2比例较低时,反应以催化为主导,形貌趋向于具有夹层的CNFs团簇。

分级结构WO_(3)-TiO_(2)-CNFs纳米复合材料的制备及其光催化性能研究

本文通过水热法在多孔碳纳米纤维(CNFs)表面负载TiO_(2)和WO_(3),成功制备了高比例暴露、光催化性能优异且易于回收的WO3-TiO_(2)-CNFs三元复合材料,研究了WO3的添加量对光催化性能的影响,采用SEM、TEM、XRD、BET、和UV-vis等手段对催化剂进行了表征,并通过降解亚甲基蓝(MB)溶液来考察其光催化性能。结果显示,WO3与TiO_(2)的最佳复合摩尔百分比为4%,经过模拟太阳光照射90min后,对15 mg/L MB溶液的降解率为97.4%,且重复使用5次之后,对MB溶液的降解率仍然保持在93.6%。

Flexural destructive process of unidirectional carbon/carbon composites reinforced with in situ grown carbon nanofibers

Unidirectional carbon/carbon（C/C） composites modified with in situ grown carbon nanofibers（CNFs） were prepared by catalysis chemical vapor deposition. The effect of in situ grown CNFs on the flexural properties of the C/C composites was investigated by detailed analyses of destructive process. The results show that there is a sharp increase in the flexural load-displacement curve in the axial direction of the CNF-C/C composites, followed by a serrated yielding phenomenon similar to the plastic materials. The failure mode of the C/C composites modified with in situ grown CNFs is changed from the pull-out of single fiber to the breaking of fiber bundles. The existence of interfacial layer composed by middle-textured pyrocarbon, CNFs and high-textured pyrocarbon can block the crack propagation and change the propagation direction of the main crack, which leads to the higher flexural strength and modulus of C/C composites.

Flexible, Porous, and Metal–Heteroatom?Doped Carbon Nanofibers as Efficient ORR Electrocatalysts for Zn–Air Battery

Developing an e cient and durable oxygen reduction electrocatalyst is critical for clean-energy technology, such as fuel cells and metal–air batteries. In this study, we developed a facile strategy for the preparation of flexible, porous, and well-dispersed metal–heteroatom-doped carbon nanofibers by direct carbonization of electrospun Zn/Co-ZIFs/PAN nanofibers(Zn/Co-ZIFs/PAN). The obtained Zn/Co and N co-doped porous carbon nanofibers carbonized at 800 °C(Zn/Co–N@PCNFs-800) presented a good flexibility, a continuous porous structure, and a superior oxygen reduction reaction(ORR) catalytic activity to that of commercial 20 wt% Pt/C, in terms of its onset potential(0.98 V vs. RHE), half-wave potential(0.89 V vs. RHE), and limiting current density(-5.26 mA cm^(-2)). In addition, we tested the suitability and durability of Zn/Co–N@PCNFs-800 as the oxygen cathode for a rechargeable Zn–air battery. The prepared Zn–air batteries exhibited a higher power density(83.5 mW cm^(-2)), a higher specific capacity(640.3 mAh g^(-1)), an excellent reversibility, and a better cycling life than the commercial 20 wt% Pt/C + RuO_2 catalysts. This design strategy of flexible porous non-precious metal-doped ORR electrocatalysts obtained from electrospun ZIFs/polymer nanofibers could be extended to fabricate other novel, stable, and easy-to-use multi-functional electrocatalysts for clean-energy technology.

Improved Na+/K+ Storage Properties of ReSe2–Carbon Nanofibers Based on Graphene Modifications

Rhenium diselenide(ReSe2) has caused considerable concerns in the field of energy storage because the compound and its composites still suffer from low specific capacity and inferior cyclic stability.In this study,ReSe2 nanoparticles encapsulated in carbon nanofibers were synthesized successfully with simple electrospinning and heat treatment.It was found that graphene modifications could affect considerably the microstructure and electrochemical properties of ReSe2–carbon nanofibers.Accordingly,the modified compound maintained a capacity of 227 mAhg-1 after 500cycles at 200 mAg-1 for Na+storage,230 mAh g-1 after 200 cycles at 200 mAg-1,212 mAh g-1 after 150 cycles at 500 mAg-1 for K+ storage,which corresponded to the capacity retention ratios of 89%,97%,and 86%,respectively.Even in Na+full cells,its capacity was maintained to 82% after 200 cycles at 1 C(117 mAg-1).The superior stability of ReSe2–carbon nanofibers benefitted from the extremely weak van der Waals interactions and large interlayer spacing of ReSe2,in association with the role of graphene-modified carbon nanofibers,in terms of the shortening of electron/ion transport paths and the improvement of structural support.This study may provide a new route for a broadened range of applications of other rhenium-based compounds.

Preparation and electrochemical properties of carbon-coated LiFePO_4 hollow nanofibers

Carbon-coated LiFePO_4 hollow nanofibers as cathode materials for Li-ion batteries were obtained by coaxial electrospinning. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller specific surface area analysis, galvanostatic charge–discharge, and electrochemical impedance spectroscopy（EIS） were employed to investigate the crystalline structure, morphology, and electrochemical performance of the as-prepared hollow nanofibers. The results indicate that the carbon-coated LiFePO_4 hollow nanofibers have good long-term cycling performance and good rate capability： at a current density of 0.2C（1.0C = 170 mA ·g^-1） in the voltage range of 2.5–4.2 V, the cathode materials achieve an initial discharge specific capacity of 153.16 mA h·g^-1 with a first charge–discharge coulombic efficiency of more than 97%, as well as a high capacity retention of 99% after 10 cycles; moreover, the materials can retain a specific capacity of 135.68 mA h·g^-1, even at 2C.

Application of activated carbon-decorated polyacrylonitrile nanofibers as an adsorbent in dispersive solid-phase extraction of fluoroquinolones from wastewater

A cheap and simple sample preparation method, consisting of a dispersive solid-phase method and an adsorbent, activated carbon decorated PAN nanofibers, was employed and used for the extraction of antibiotics(ciprofloxacin, danofloxacin, and enrofloxacin) in wastewater. Electrospun PAN nanofibers that were decorated with activated carbon produced from waste tires were used as the solid phase and the antibiotics analyzed by using high-performance liquid chromatography. Parameters such as pH, mass of adsorbent(MA),extraction volume(EV), and extraction time(ET) were optimized owing to their potential effect on the extraction of antibiotics from water. The recovery of all antibiotics was satisfactory, in the range of 90%–99%.The limits of detection and quantification were 0.05, 0.11, 0.20, and 0.53, 1.21, 2.17 mg/L, respectively. The precision was determined from the repeatability and reproducibility and expressed as the intra-day(n=20)and inter-day(n=5) precision. The intra-day and inter-day precision was reported in terms of the percentage relative standard deviation, which was 3% and 4%, respectively. The adsorption capacity of the activated carbon-decorated PAN nanofibers was satisfactory, and the reusability of the adsorbent was impressive when reused ten times. The accuracy of the dispersive solid phase extraction(DSPE) was validated by spike recovery tests; the results proved the reliability and efficiency of adsorbing antibiotics from wastewater. Finally, the proposed method was applied to wastewater samples collected from a wastewater treatment plant, which included influent, secondary, and effluent wastewater.

N, F?Codoped Microporous Carbon Nanofibers as Efficient Metal?Free Electrocatalysts for ORR

Currently, the oxygen reduction reaction(ORR) mainly depends on precious metal platinum(Pt) catalysts. However, Pt-based catalysts have several shortcomings, such as high cost, scarcity, and poor long-term stability. Therefore, development of e cient metal-free electrocatalysts to replace Pt-based electrocatalysts is important. In this study, we successfully prepared nitrogen-and fluorinecodoped microporous carbon nanofibers(N, F-MCFs) via electrospinning polyacrylonitrile/polyvinylidene fluoride/polyvinylpyrrolidone(PAN/PVDF/PVP) tricomponent polymers followed by a hydrothermal process and thermal treatment, which was achieved for the first time in the literature. The results indicated that N, F-MCFs exhibit a high catalytic activity(E_(onset): 0.94 V vs. RHE, E_(1/2): 0.81 V vs. RHE, and electron transfer number: 4.0) and considerably better stability and methanol tolerance for ORR in alkaline solutions as compared to commercial Pt/carbon(Pt/C, 20 wt%) catalysts. Furthermore, in acidic media, N, F-MCFs showed a four-electron transfer pathway for ORR. This study provides a new strategy for in situ synthesis of N, F-MCFs as highly e cient metal-free electrocatalysts for ORR in fuel cells.

N-doped porous carbon nanofibers sheathed pumpkin-like Si/C composites as free-standing anodes for lithium-ion batteries

Dramatic capacity fading and poor rate performance are two main obstacles that severely hamper the widespread application of the Si anode owing to its large volume variation during cycling and low intrinsic electrical conductivity.To mitigate these issues,free-standing N-doped porous carbon nanofibers sheathed pumpkin-like Si/C composites(Si/C-ZIF-8/CNFs)are designed and synthesized by electrospinning and carbonization methods,which present greatly enhanced electrochemical properties for lithium-ion battery anodes.This particular structure alleviates the volume variation,promotes the formation of stable solid electrolyte interphase(SEI)film,and improves the electrical conductivity.As a result,the as-obtained free-standing Si/C-ZIF-8/CNFs electrode delivers a high reversible capacity of 945.5 mAh g^(-1) at 0.2 A g^(-1) with a capacity retention of 64% for 150 cycles,and exhibits a reversible capacity of 538.6 mA h g^(-1) at 0.5 A g^(-1) over 500 cycles.Moreover,the full cell composed of a freestanding Si/C-ZIF-8/CNFs anode and commercial LiNi_(1/3)Co_(1/3)Mn_(1/3)O_(2)(NCM)cathode shows a capacity of 63.4 mA h g^(-1) after 100 cycles at 0.2 C,which corresponds to a capacity retention of 60%.This rational design could provide a new path for the development of high-performance Si-based anodes.

Stepwise Fabrication of Co-Embedded Porous Multichannel Carbon Nanofibers for High-Efficiency Oxygen Reduction

A novel nonprecious metal material consisting of Coembedded porous interconnected multichannel carbon nanofibers(Co/IMCCNFs) was rationally designed for oxygen reduction reaction(ORR)electrocatalysis.In the synthesis,ZnCo2O4 was employed to form interconnected mesoporous channels and provide highly active Co3O4/Co core–shell nanoparticle-based sites for the ORR.The IMC structure with a large synergistic effect of the N and Co active sites provided fast ORR electrocatalysis kinetics.The Co/IMCCNFs exhibited a high half-wave potential of 0.82 V(vs.reversible hydrogen electrode) and excellent stability with a current retention up to 88% after 12,000 cycles in a current–time test,which is only 55% for 30 wt% Pt/C.

Effective Modified Carbon Nanofibers as Electrodes for Capacitive Deionization Process

Carbon materials have the advantages of good electrical conductivity and excellent chemical stability, so many carbon materials have been introduced as electrodes for the capacitive deionization (CDI) process. Due to the low surface area compared to the other nanocarbonaceous materials, CNFs performance as electrode in the CDI units is comparatively low. This problem has been overcome by preparing high surface area carbon nanofibers and by creating numerous long pores on the nanofibers surface. The modified CNFs have been synthesized using low cost, high yield and facile method;electrospinning technique. Stabilization and graphitization of electrospun nanofiber mats composed of polyacrylonitrile (PAN) and poly (methyl methacrylate) (PMMA) leads form longitudinal pores CNFs. The utilized characterizations indicated that the CNFs obtained from electrospun solution having 50% PMMA have surface area of 181 m2/g which are more than the conventional CNFs. Accordingly, these nanofibers revealed salt removal efficiency of ~90% and specific capacitance of 237 F/g.

Porous nitrogen-enriched hollow carbon nanofibers as freestanding electrode for enhanced lithium storage

Onedimensional porous carbons bearing high surface areas and sufficient heteroatom doped functionalities are essential for advanced electrochemical energy storage devices,especially for developing freestanding film electrodes.Here we develop a porous,nitrogenenriched,freestanding hollow carbon nanofiber(PNFHCF)electrode material via filtration of polypyrrole(PPy)hollow nanofibers formed by in situ selfdegraded templateassisted strategy,followed by NH3assisted carbonization.The PNFHCF retains the freestanding film morphology that is composed of threedimensional networks from the entanglement of 1D nanofiber and delivers 3.7fold increase in specific surface area(592 m^(2)g^(-1))compared to the carbon without NH_(3)treatment(FHCF).In spite of the enhanced specific surface area,PNFHCF still exhibits comparable high content of surface N functionalities(8.8%,atom fraction)to FHCF.Such developed hierarchical porous structure without sacrificing N doping functionalities together enables the achievement of high capacity,highrate property and good cycling stability when applied as selfsupporting anode in lithiumion batteries,superior to those of FHCF without NH3 treatment.