N-doped Carbon Fibers Research Articles

SnO2 nanoparticles confined by N-doped and CNTs-modified carbon fibers as superior anode material for sodium-ion battery

In the present work, carbon nanofibers (CNFs) decorated with carbon nanotubes (CNTs) and SnO2 nanoparticles (SnO2@CNFs/CNTs) were synthesized through electrospinning technique and following thermal treatment. Due to the flexible fibrous structure of composite, the as-obtained mats can be directly utilized as free-standing anodes for SIBs. Thanks to the in-situ introduced CNTs, the harsh carbonization treatment condition can be simplified. In addition, excellent electrochemical performances were obtained when the optimized composite was applied as anodes for SIBs. Specifically, a discharge capacity of 460.3 mAh g−1 can be maintained after 200 cycles. Besides, 222.2 mAh g−1 can be delivered even at a high current density of 3.2 A g−1. These results demonstrate that the as-obtained anodes possess a highly stable cycling performance and excellent rate capabilities. The approach we proposed shows great prospect for practical application.

Understanding High-Energy-Density Sn4P3 Anodes for Potassium-Ion Batteries

Summary Phosphorus-based anodes for alkali metal-ion batteries are attractive due to their high theoretical-specific capacity. However, their poor electrochemical performance caused by relatively large volume variations during cycling, low electrical conductivity, and severe electrolyte decomposition due to highly reactive phosphide surface hinder their potential applications. Herein, we confine Sn4P3 in N-doped carbon fibers as anode for potassium-ion batteries with enhanced cycling stability and high rate capability (160.7 mA hr g−1 after 1,000 cycles at 500 mA g−1). The Sn4P3 anodes undergo a sequential conversion (P to K3P11, K3P) and alloying (Sn to KSn) reactions with synergistic K-storage mechanisms. Also, the electrolyte with potassium bis(fluorosulfonyl)imide salt can effectively suppress the dendrite growth in K stripping/plating, stabilize the solid-electrolyte interphase (SEI) layer, and avoid excessive side reactions, thus enhancing the electrode stability. This work provides a feasible approach to overcome the durability bottlenecks of K-ion batteries through regulating dendrite growth and SEI formation.

Highly nitrogen-doped graphitic carbon fibers from sustainable plant protein for supercapacitor

In this research, a novel biomass-based, highly nitrogen-doped carbon fiber material has been synthesized from electrospun plant protein fibers by one-step carbonization. The material fibrous structure was well maintained during pyrolysis by incorporating Ca2+ in the protein fiber matrix, since Ca2+ increased the thermal stability of the protein and the calcium salt/oxide provided a solid support during pyrolysis. In addition, the calcium salt served as a template to generate pores on the carbon samples. X-ray photoelectron spectra showed that the fibrous carbon materials possessed large nitrogen content (7.5%), mainly in the form of pyridonic/pyrrolic and pyridinic nitrogen. The optimized sample P-10% Ca-CL exhibited an interconnected carbon fiber network with meso and micropores on the fiber surface. Moreover, the well aligned granular graphitic structure observed embedded within the carbon fibers, which has been found for the first time from biomass derived carbon fiber materials. The optimized carbon fibers (P-10% Ca-CL) showed an exceptional areal specific capacitance of 64 μF/cm2 at 0.5 A/g. This is attributed to the large number of N functional groups which induced a pseudocapacitance and improved the wettability of the carbon surface. The carbon fibers also exhibited excellent cyclic stability with 98% retention after 5000 cycles at a current density of 10 A/g. This research is the first publication of highly N-doped carbon fibers derived from plant proteins and show potential to be used as a supercapacitor electrode. Additionally, these materials were prepared by a convenient and environmentally-friendly method, not requiring a large energy input or corrosive chemicals.

Facile Synthesis of Palladium-Nanoparticle-Embedded N-Doped Carbon Fibers for Electrochemical Sensing.

In recent years, there have been many studies on metal/carbon hybrid materials for electrochemical applications. However, reducing the metal content in catalysts is still a challenge. Here, a facile synthesis of palladium (Pd) nanoparticle-embedded N-doped carbon fibers (Pd/N-C) through electropolymerization and reduction methods is demonstrated. The as-prepared Pd/N-C contains only 1.5 wt % Pd. Under optimal conditions, bisphenol A is detected by using amperometry in two dynamic ranges from 0.1 to 10 μm and from 10 to 200 μm, and the obtained correlation coefficients are close to 0.9836 and 0.9987, respectively. The detection limit (DL) for bisphenol A is determined to be 29.44 (±0.77) nm.

NiCoSe2-x/N-doped C mushroom-like core/shell nanorods on N-doped carbon fiber for efficiently electrocatalyzed overall water splitting

Developing stable and efficient bifunctional catalysts for overall water splitting is a critical step in the production of renewable energy sources. Here we report a stable and highly active electrocatalyst comprised of NiCoSe2-x/N-doped carbon mushroom-like core/shell nanorods on silk-derived carbon fiber through one step selenization. The unique one-dimensional nanorod structure facilitates the charge transport, and the N-doped carbon shell also increases the electrical conductivity, resulting in a remarkable enhancement of the catalytic activity. The N-doped carbon shell also functions as a protection layer. The composite catalyst therefore exhibits outstanding OER and HER performance, it can also stably drive the overall water splitting at a low cell voltage of 1.53 V in base solution. The present work provides an efficient strategy for the fabrication of stable and active electrocatalysts with earth-abundant elements.

Raw-Cotton-Derived N-Doped Carbon Fiber Aerogel as an Efficient Electrode for Electrochemical Capacitors

The carbon fiber aerogel with a high surface area, as a promising ideal electrode for electrochemical capacitors (ECs), has attracted tremendous attention because it can offer a fast charge–discharge rate and an exceptional rate capability. However, there is still a big challenge to acquire highly porous fiber aerogel with elastic properties and good flexibility. Herein, N-doped porous carbon fiber aerogel (N-CFA) has been successfully fabricated using raw cotton as a fibrous template to obtain shaped aerogels. ZIF-8, in situ fabricated on the surface of cotton, played the role of an active agent and nitrogen source to create a rich porous structure with a certain nitrogen content. Benefiting from the macromonolith morphology with good flexibility, favorable mechanical durability, nitrogen doping, anda high specific surface area, the N-CFA exhibits excellent electrochemical performance with a high capacity of 365 F g–1 at a current of 0.5 A g–1 and a remarkable rate capability of 65.8% from 0.5 to 100 A g...

Growth of SnO2 Nanoflowers on N-doped Carbon Nanofibers as Anode for Li- and Na-ion Batteries

It is urgent to solve the problems of the dramatic volume expansion and pulverization of SnO2 anodes during cycling process in battery systems. To address this issue, we design a hybrid structure of N-doped carbon fibers@SnO2 nanoflowers (NC@SnO2) to overcome it in this work. The hybrid NC@SnO2 is synthesized through the hydrothermal growth of SnO2 nanoflowers on the surface of N-doped carbon fibers obtained by electrospinning. The NC is introduced not only to provide a support framework in guiding the growth of the SnO2 nanoflowers and prevent the flower-like structures from agglomeration, but also serve as a conductive network to accelerate electronic transmission along one-dimensional structure effectively. When the hybrid NC@SnO2 was served as anode, it exhibits a high discharge capacity of 750 mAh g−1 at 1 A g−1 after 100 cycles in Li-ion battery and 270 mAh g−1 at 100 mA g−1 for 100 cycles in Na-ion battery, respectively.

Electrospun mulberry-like hierarchical carbon fiber web for high-performance supercapacitors

In this work, we have fabricated a kind of N-doped hierarchal carbon fiber web by electrospinning hollow mesoporous carbon spheres (HMCSs) into fibrous structure. The as-synthesized carbon fiber web with novel mulberry-like morphology, thus denoted as MC-FW, possesses micro/meso/macroporous porosity, large surface area, high conductivity and multi-level structure, which are highly desired for supercapacitor electrode materials. The electrochemical measurements demonstrate that the designed MC-FW shows high capacitance (298.6 F g−1), favorable capacitance retention (71.0%) and long cycle life (97.3% capacitance retention after 5000 cycles). Notably, the capacitance of 298.6 F g−1 for MC-FW is higher than the capacitance reported so far for many hollow carbon spheres and carbon fibers, which may contribute to the synergistic effect between the merits of HMCSs (e.g. micro/meso/macroporous hierarchal structure, large surface area, high pore volume) and advantages of 1D carbon fiber (e.g. large aspect ratio and high conductivity). It is believed that this distinctive carbon fiber web may show promising prospects as advanced energy storage materials and catalyst.

Three-dimensional cross-linked Polyaniline fiber/N-doped porous carbon with enhanced electrochemical performance for high-performance supercapacitor

In this work, we design a novel and facile strategy to synthesize a three-dimensional (3D) cross-linked structural composite with PANI and MOF-derived N-doped porous carbon composite (3CPC). The novel and facile method realize interconnected structure composed of an ultrahigh surface area of N-doped porous carbon and conductive PANI fiber, which can offer more contact area between the electrode material and electrolyte to provide more active sites for charge storage and shorten the pathway for electron transfer. As a result, the 3CPC shows an extraordinarily efficient specific capacity of 755 F g−1 and good cycling stability at a current density of 1 A g−1 in 1 M H2SO4, which suggests its potential application as an efficient material for supercapacitor.

Binder-free Li3V2(PO4)3/C membrane electrode supported on 3D nitrogen-doped carbon fibers for high-performance lithium-ion batteries

An in-situ prepared binder-free Li3V2(PO4)3/C membrane electrode supported on 3D N-doped carbon fibers (LVP/C@NCF) has been developed. The residual carbon in LVP/C@NCF consists of the pyrolytic carbon from glucose and the N-doped carbon fibers decomposed from filter paper. The former uniformly covers on the surface of LVP particles, while the latter is functioned as both a 3D conductive network and a current collector for LVP. Compared with the traditional LVP/C electrode supported on Al foil (LVP/C@Al), the LVP/C@NCF membrane electrode displays higher rate capability and better cycle stability. Especially, when cycled at a high rate of 10C, it still delivers a specific capacity as high as 107.6mAhg−1 with a very low capacity fading ratio of ~0.0048% per cycle after 1000 cycles. The excellent electrochemical performance is ascribed to the synergetic effect from the 3D effectively conductive network and the in-situ produced current collector of carbon fibers. The method of using filter paper as the source of carbon and current collector to prepare integrated membrane electrode may provide feasible and effective strategy to fabricate binder-free flexible and lightweight lithium ion batteries as well as sodium ion batteries.

A host-guest approach to fabricate metallic cobalt nanoparticles embedded in silk-derived N-doped carbon fibers for efficient hydrogen evolution

Hydrogen evolution reaction (HER) plays a key role in generating clean and renewable energy. As the most effective HER electrocatalysts, Pt group catalysts suffer from severe problems such as high price and scarcity. It is highly desirable to design and synthesize sustainable HER electrocatalysts to replace the Pt group catalysts. Due to their low cost, high abundance and high activities, cobalt-incorporated N-doped nanocarbon hybrids are promising candidate electrocatalysts for HER. In this report, we demonstrated a robust and eco-friendly host-guest approach to fabricate metallic cobalt nanoparticles embedded in N-doped carbon fibers derived from natural silk fibers. Benefiting from the one-dimensional nanostructure, the well-dispersed metallic cobalt nanoparticles and the N-doped thin graphitized carbon layer coating, the best Co-based electrocatalyst manifests low overpotential (61 mV@10 mA/cm2) HER activity that is comparable with commercial 20% Pt/C, and good stability in acid. Our findings provide a novel and unique route to explore high-performance noble-metal-free HER electrocatalysts.

Electrospun metal-organic framework derived hierarchical carbon nanofibers with high performance for supercapacitors.

A novel N-doped MOF-based hierarchical carbon fiber (NPCF) towards supercapacitors was prepared by the pyrolysis of MOF nanofibers. Due to its unique 1D hollow structures, the NPCF exhibits better energy storage capacity than the other previously reported MOF-derived carbon materials.

Fe/N decorated mulberry-like hollow mesoporous carbon fibers as efficient electrocatalysts for oxygen reduction reaction

Developing oxygen reduction reaction (ORR) catalysts with high performance at low cost is critical for the practical application of fuel cell technology. In this work, novel Fe-N-C hybrid mulberry-like fibers (denoted as MB-CFs), which are composed of hollow mesoporous carbon spheres (HMCSs) encapsulated in N-doped carbon fiber, have been synthesized by a facile electrospinning method. These composite materials have successfully combined together the merits of HMCSs (i.e. high surface area and micro-meso-macropores) and carbon fibers (i.e. large aspect ratio, high conductivity, and favorable flexibility), as well as graphitic and multilevel structure, which are highly desired as ORR catalysts. The electrochemical measurements demonstrate that the designed MB-CFs-0.6 was the best among the series, which possess outstanding activity, excellent durability and selectivity toward ORR catalytic reaction in both alkaline and acid media. Considering the favorable structure and ORR performance of this novel carbon fiber, other nanoparticles (heteroatom or metal-doped hierarchical porous carbon spheres, hollow metal oxides, etc.) could also be electrospun into functional carbon fibers for energy storage and conversion.

Two-dimensional molybdenum disulfide and tungsten disulfide interleaved nanowalls constructed on silk cocoon-derived N-doped carbon fibers for hydrogen evolution reaction

Finding cost-effective, active and durable catalyst materials for energy applications, such as electrocatalytic hydrogen production, is an intriguing challenge. Here, a facile and effective approach to the design and construction of two-dimensional MoS2 and WS2 interleaved nanowalls with maximum exposures of active edges on silk-derived N-doped carbon fibers (SNCF) was demonstrated. The morphological evolutions of the MoS2 and WS2 nanocrystals on the SNCF from crescent-like nanosheets to an interleaved nanowall network can be obtained by adjusting the concentrations of the Mo and W precursors. These robust MoS2/SNCF and WS2/SNCF electrocatalysts exhibit prominent hydrogen evolution reaction (HER) activities with onset potentials of −40 and −96 mV and Tafel slopes of 60 and 66 mV dec−1, respectively. The overpotentials (η) at j = −10 mA cm−2 for MoS2/SNCF and WS2/SNCF are −102 and −157 mV, respectively. In addition, MoS2/SNCF and WS2/SNCF are both able to sustain continuous HER operation for 10 h under working conditions with only a slight degradation in current densities, implying excellent durability and a prospect for practical applications.

Co-embedded N-doped carbon fibers as highly efficient and binder-free cathode for Na–O2 batteries

High energy density Na-O2 batteries is very promising for large scale energy storage, wherein the critical bottleneck lies in poor energy efficiency and cycle stability stemming from low catalytic activity and unstable structure of cathode. Herein, we propose a highly effective strategy to activate and stabilize low cost while inefficient N-doped carbon fibers by in situ simultaneous Co embedding/coating. Unexpectedly, the obtained binder-free cathode endows Na-O2 battery with superior electrochemical performances, including low charge overpotential, high specific capacity, and especially good cycle stability, which could be attributed to the combined advantages associated with facilitated electron and mass transportation due to fiber shape and binder-free and porous structure, high conductivity and catalytic activity derived from the synergy between N-doped carbon fibers and Co (metallic and partially oxidized Co) as well as the successful tailor of the morphology of discharge products.

Immobilization of NiS nanoparticles on N-doped carbon fiber aerogels as advanced electrode materials for supercapacitors

NiS nanoparticles (NPs) with excellent electrochemical capacitance have attracted considerable attention as cost-effective energy-storage materials for supercapacitors in recent years. Preventing the aggregation and increasing the conductivity of NiS NPs are key to fully realizing their excellent electrochemical properties. In this work, NiS/N-doped carbon fiber aerogel (N-CFA) nanocomposites were obtained easily through the combination of polymerization, carbonization, and a one-step solvothermal reaction. N-CFA derived from polydopamine (PDA)-coated cotton wool was used as a template for the construction of hierarchical NiS/N-CFA nanocomposites, in which NiS NPs are uniformly immobilized on the surface of N-CFA. In this nanostructured system, N-CFA containing abundant nanofibers not only provides active regions for the growth of NiS NPs to prevent their aggregation, but also offers short pathways for the transport of electrons and ions. The electrochemical properties of the obtained NiS/N-CFA nanocomposites were investigated by cyclic voltammetry, galvanostatic charge–discharge, and alternating current impedance measurements. The optimized NiS/N-CFA nanocomposite exhibits a high specific capacitance of 1,612.5 F·g‒1 at a charge/discharge current density of 1 A·g‒1 and excellent rate capacitance retention of 66.7% at 20 A·g‒1. The excellent electrochemical properties of NiS/N-CFA nanocomposites make these materials promising electrode materials for supercapacitors.

Synthesis of SnO2 versus Sn crystals within N-doped porous carbon nanofibers via electrospinning towards high-performance lithium ion batteries.

The design of tin-based anode materials (SnO2 or Sn) has become a major concern for lithium ion batteries (LIBs) owing to their different inherent characteristics. Herein, particulate SnO2 or Sn crystals coupled with porous N-doped carbon nanofibers (denoted as SnO2/PCNFs and Sn/PCNFs, respectively) are fabricated via the electrospinning method. The electrochemical behaviors of both SnO2/PCNFs and Sn/PCNFs are systematically investigated as anodes for LIBs. When coupled with porous carbon nanofibers, both SnO2 nanoparticles and Sn micro/nanoparticles display superior cycling and rate performances. SnO2/PCNFs and Sn/PCNFs deliver discharge capacities of 998 and 710 mA h g(-1) after 140 cycles (at 100, 200, 500 and 1000 mA g(-1) each for 10 cycles and then 100 cycles at 100 mA g(-1)), respectively. However, the Sn/PCNF electrodes show better cycling stability at higher current densities, delivering higher discharge capacities of 700 and 550 mA h g(-1) than that of SnO2/PCNFs (685 and 424 mA h g(-1)) after 160 cycles at 200 and 500 mA g(-1), respectively. The different superior electrochemical performance is attributed to the introduction of porous N-doped carbon nanofibers and their self-constructed networks, which, on the one hand, greatly decrease the charge-transfer resistance due to the high conductivity of N-doped carbon fibers; on the other hand, the porous carbon nanofibers with numerous voids and flexible one-dimensional (1D) structures efficiently alleviate the volume changes of SnO2 and Sn during the Li-Sn alloying-dealloying processes. Moreover, the discussion of the electrochemical behaviors of SnO2vs. Sn would provide new insights into the design of tin-based anode materials for practical applications, and the current strategy demonstrates great potential in the rational design of metallic tin-based anode materials.

Self-supported bimodal-pore structured nitrogen-doped carbon fiber aerogel as electrocatalyst for oxygen reduction reaction

Self-supported 3-dimensional (3D) nitrogen-doped bimodal-pore structured carbon fiber aerogel is synthesized via a facile carbonization process using prawn shells as the raw material. The fabricated N-doped carbon fiber aerogel possesses micro- and meso-porous pores with an N doping level of 5.9% and a high surface area of 526m2g−1. As an electrocatalyst, the resultant N-doped carbon fiber aerogel exhibits superior electrocatalytic activity towards oxygen reduction reaction (ORR) with a more positive ORR onset-potential, better stability and high resistance to crossover effect compared to the commercial Pt/C electrocatalyst.

Vertically Aligned N-Doped Coral-like Carbon Fiber Arrays as Efficient Air Electrodes for High-Performance Nonaqueous Li–O2 Batteries

High energy efficiency and long cycleability are two important performance measures for Li-air batteries. Using a rationally designed oxygen electrode based on a vertically aligned nitrogen-doped coral-like carbon nanofiber (VA-NCCF) array supported by stainless steel cloth, we have developed a nonaqueous Li-O2 battery with an energy efficiency as high as 90% and a narrow voltage gap of 0.3 V between discharge/charge plateaus. Excellent reversibility and cycleability were also demonstrated for the newly developed oxygen electrode. The observed outstanding performance can be attributed to its unique vertically aligned, coral-like N-doped carbon microstructure with a high catalytic activity and an optimized oxygen/electron transportation capability, coupled with the microporous stainless steel substrate. These results demonstrate that highly efficient and reversible Li-O2 batteries are feasible by using a rationally designed carbon-based oxygen electrode.