Nitrogen-doped Carbon Nanofibers Research Articles

Electro-spun Sn nanoparticles encapsulated in N-doped carbon nanofibers as flexible integrated anodes for high-efficiency lithium-ion batteries

The anode electrode substances of lithium-ion batteries (LIBs) are indispensable for the insertion and elimination of Li+. Herein, we combine electrospinning technology and heat treatment method to encapsulate Sn species in nitrogen-doped carbon nanofibers (Sn/NCNFs). During the experiment, we selected polyacrylonitrile (PAN) as the precursor solution, tetraphenyl porphyrin (TPP) as the N source and SnCl2·as the Sn source. The obtained one-dimensional structure no longer only successfully reduces the giant extent modifications of Sn species in the course of cycling, but additionally achieves fast Li+/e− transportation. Moreover, the introduction of N atoms causes more defects in carbon nanofibers, providing additional storage sites for Li+. Thus, the Sn/NCNF-0.168 exhibits favorable reversible capacity (~581.7 mAh g−1 at 1 A g−1) and cycling stability (over 250 cycles). This work gives an advantageous strategy to design high-performance anode electrode substances for LIBs and lays the foundation for future energy applications.

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 (E1/2) 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 E1/2 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.

Direct methanol fuel cell with enhanced oxygen reduction performance enabled by CoFe alloys embedded into N-doped carbon nanofiber and bamboo-like carbon nanotube

The exploration of cost-effective electrocatalysts with high catalytic activity and methanol tolerance to replace precious metal catalysts in the oxygen reduction reaction (ORR) is highly desirable for direct methanol fuel cells (DMFCs). Herein, we report a novel complex composed of a CoFe alloy with a modulated electronic structure confined to nitrogen-doped carbon nanofiber (NCNF) and bamboo-like carbon nanotube (BCNT) by tuning the molar ratio of Co and Fe (CoFe@NCNF/BCNT). The synthetized catalysts possess one-dimensional (1D) mesoporous structure, high specific surface area, and rich pyridinic-N content. Notably, the Co1Fe1@NCNF/BCNT and Co1Fe3@NCNF/BCNT (Co:Fe ≈ 1:1 and 1:3) exhibited enhanced oxygen reduction activity and methanol tolerance, compared to unmodified samples. In addition, alkaline DMFCs containing Co1Fe1@NCNF/BCNT and Co1Fe3@NCNF/BCNT presented high power density (29.10 and 31.11 mW cm−2), exceeding that of Pt/C-modified DMFC (27.23 mW cm−2). Furthermore, the Co1Fe1@NCNF/BCNT-catalyzed DMFC exhibited high stability. This improved catalytic activity can be attributed to the rich surface area, controllable alloy composition, optimized N configuration, and favorable electronic interaction. The as-developed CoFe@NCNF/BCNT with multifunctional components may open a new avenue for designing highly active cathode catalysts for various fuel cells.

Nitrogen-doped porous carbon nanofibers embedded with Cu/Cu3P heterostructures as multifunctional current collectors for stabilizing lithium anodes in lithium-sulfur batteries

Among the various beyond-lithium-ion battery systems, lithium-sulfur batteries (Li-S) have been widely considered as one of the most promising technologies owing to their high theoretical energy density. However, the irregular Li plating/stripping and infinite volume change associated with low Coulombic efficiency and safety concerns of host-less lithium anode hinder the practical application of Li-S batteries. Herein, Cu/Cu3P heterostructure-embedded in carbon nanofibers (Cu/Cu3P-N-CNFs) are developed as multifunctional current collectors for regular lithium deposition. The 3D porous interconnected carbon skeleton endows effectively reduced local current density and volume expansion, meanwhile the Cu/Cu3P particles function as nucleation sites for uniform lithium plating. Consequently, the developed ion/electron-conducting skeleton delivers remarkable electrochemical performances in terms of high Coulombic efficiency for 500 cycles at 1 mA cm−2, and the accordingly symmetric cell exhibits long-term cyclic duration over 1500 h with a low voltage hysteresis of ∼ 80 mV at 1 mA cm−2. Moreover, Li-S full cells paired with the developed anode and S@CNTs cathode also show superior rate capability (568 mAh/g at 2C) and excellent stability of >500 cycles at 0.2C, further demonstrating the great potential of Cu/Cu3P-N-CNFs as promising current collectors for advanced lithium-metal batteries.

Magnetic nitrogen-doped carbon nanofibers containing homogeneously dispersed CoFe2O4 nanoparticles with lightweight and efficient microwave absorption performance

Homogeneously dispersed ultrafine CoFe2O4 nanoparticles embedded within N-doped carbon nanofibers (named as CFO@NCNFs) have been fabricated via electrospinning and following heat treatment procedures. The dielectric and magnetic parameters of CFO@NCNFs/paraffin wax composites are regulated through adjusting the concentration of CoFe2O4 to obtain good impedance matching and excellent microwave absorption (MA) properties. Benefiting from the unique structure involving CoFe2O4 @onion-like carbon nanospheres and 3D conductive NCNFs network, as well as the synergistic mechanism between ultrasmall magnetic CoFe2O4 nanoparticles and light mass dielectric NCNFs. The CFO@NCNFs-5 exhibit outstanding MA properties at only 20 wt% filler loading and minimum reflection loss (RL) achieves −47.9 dB (surpass 99.9% MA) at 9.2 GHz with a thin thickness of merely 1.7 mm, and the corresponding effective absorption bandwidth (RL < −10 dB) achieves 5.4 GHz (6.5–11.9 GHz). Moreover, the effective absorption bandwidth (EAB) can be obtained in multiband (3.9–18.0 GHz) by adjusting the thickness of sample layer. Our work indicates that the appropriate incorporation of ultrafine CoFe2O4 nanoparticles encapsulated in NCNFs is a versatile and high-efficiency strategy to integrate lightweight and excellent properties of magnetic carbon-based absorbers.

Defect-Engineered Fe3C@NiCo2S4 Nanospike Derived from Metal-Organic Frameworks as an Advanced Electrode Material for Hybrid Supercapacitors.

The rational synthesis and tailoring of metal-organic frameworks (MOFs) with multifunctional micro/nanoarchitectures have emerged as a subject of significant academic interest owing to their promising potential for utilization in advanced energy storage devices. Herein, we explored a category of three-dimensional (3D) NiCo2S4 nanospikes that have been integrated into a 1D Fe3C microarchitecture using a chemical surface transformation process. The resulting electrode materials, i.e., Fe3C@NiCo2S4 nanospikes, exhibit immense potential for utilization in high-performance hybrid supercapacitors. The nanospikes exhibit an elevated specific capacity (1894.2 F g-1 at 1 A g-1), enhanced rate capability (59%), and exceptional cycling stability (92.5% with 98.7% Coulombic efficiency) via a charge storage mechanism reminiscent of a battery. The augmented charge storage characteristics are attributed to the collaborative features of the active constituents, amplified availability of active sites inherent in the nanospikes, and the proficient redox chemical reactions of multi-metallic guest species. When using nitrogen-doped carbon nanofibers as the anode to fabricate hybrid supercapacitors, the device exhibits high energy and power densities of 62.98 Wh kg-1 and 6834 W kg-1, respectively, and shows excellent long-term cycling stability (95.4% after 5000 cycles), which affirms the significant potential of the proposed design for applications in hybrid supercapacitors. The DFT study showed the strong coupling of the oxygen from the electrolyte OH- with the metal atom of the nanostructures, resulting in high adsorption properties that facilitate the redox reaction kinetics.

A hybrid flexible N-doped candle-soot carbon nanofibers for binder-free lithium-ion battery anode

This work demonstrates a unique fractal-like candle soot-derived carbon nanoparticles (CSC) decorated onto nitrogen-doped carbon nanofibers (CSC@N-CNFs) by a one-step electrospinning process as a self-standing flexible anode for lithium-ion battery (LIB). The CSC nanoparticles exhibit a short-range ordered structure with large interlayer spacing for enhanced Li ion storage. In addition, the N-CNFs provide flexibility and stability to prevent volume expansion during electrochemical reactions. The synergistic impact of the hybrid structure provides the flexible anode with a high initial discharge capacity of 1030 mAh/g at 0.1C with an outstanding coulombic efficiency of ∼100% at 30C (5 A/g). The enhanced performance is due to the increased electrical conductivity from N-doping from CNFs, the hard carbon morphology of CSC nanoparticles, the 3D interconnected nanofiber framework, and the binder-free flexible nature.

Excellent performance of nitrogen-doped carbon nanofibers as electrocatalysts for water splitting reactions

Green hydrogen production by water electrolysis with the least possible energy waste requires the application of suitable electrocatalytic electrodes. In this work, highly active, free-standing electrodes were prepared by deposition of nitrogen-doped carbon nanofibers (N-CNFs) on oxidized carbon cloth. Different types of N-CNFs with variable structures, nitrogen dopant concentrations and defect contents were synthesized. Their electrocatalytic activities as hybrids with oxidized and raw carbon cloth electrodes were evaluated in the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). We show that the N–CNF sample with the highest nitrogen doping in the series (6.7 at.%) and the predominance of well-ordered herringbone/bamboo-like structure with abundant edge sites, exhibited both the highest OER and HER activities (with overpotentials of 330 and 410 mV, respectively at j = ±10 mA cm−2) and excellent performance stability. The hybrid material provided abundant active sites on N-CNFs that show good adhesion to the hydrophilic carbon cloth.

Capacitive behavior dominated persistent lithium storage in the 3D carbon nanofibers with 1D molybdenum sulfide

As the anode material of lithium ion battery, molybdenum disulfide (MoS2) has a theoretical capacity far exceeding that of graphite. However, its development is greatly limited by the structural changes and low conductivity during the cycle. Here, we prepared three-dimensional (3D) nitrogen doped carbon nanofibers embedded with MoS2 nanorods by electrospinning and hydrothermal methods. One dimensional (1D) MoS2 nanorods are perfectly distributed in the carbon nanofibers along the axial direction, improving the stability and promoting the rapid insertion/removal of lithium ions. The outer molybdenum sulfide sheet provides more reactive sites, and the hierarchical nanostructures with high conductivity are constructed to obtain lithium ion storage materials dominated by high capacitance behavior. At the same time, it maintains the capacity of 736.7 mAh/g under the high current density of 5 A/g, showing excellent long cycle stability. This work provides a new possibility for the study of long cycle stable lithium ion storage at high rates.

Engineering the electronic structure of platinum single-atom sites via tailored porous carbon nanofibers for large-scale hydrogen production

Pt single-atom catalysts are promising for efficient hydrogen evolution reactions (HER) due to their ultra-high catalytic activity and atomic utilization. However, developing a scalable preparation method of binder-free Pt single-atom catalysts with optimal electronic structures for large-scale hydrogen production is still a serious challenge. In this work, we fabricated tailored nitrogen-doped porous carbon nanofibers as a support for engineering the electronic structure of Pt single-atom sites via initial micropore trapping and subsequent optimized nitrogen/carbon anchoring. The as-prepared Pt single-atom catalysts exhibited impressively enhanced HER activity and satisfactory stability, superior to the state-of-the-art single-atom catalysts. X-ray absorption structure analysis combined with theoretical simulation demonstrated the mechanisms for HER performance improvement. In particular, the free-standing Pt single-atom catalysts for a binder-free electrode showed a low overpotential of 64 mV even at 500 mA cm−2, indicating promising application for the large-scale hydrogen production.

Hierarchical porous carbon nanofibers with facilely accessible iron-based active sites for efficient oxygen reduction in alkaline and acidic media

Reasonable design of hierarchically porous structures with mass transport maximization and highly accessible active sites still remains a great challenge. Herein, we successfully fabricated Fe3O4 nanoparticles embedded in the nitrogen-doped hierarchical porous carbon nanofibers as efficient and durable electrocatalysts for oxygen reduction reaction (ORR), which was synthesized by a stepwise electrospinning-pyrolysis strategy. The unique hierarchically porous carbon nanofibers could not only improve the dispersion and exposure of metal active sites, but also maximize the mass transport, thereby enhancing the accessibility of active sites and chemical reaction rate with efficient transport channels for reactants and products. Remarkably, the optimized sample (Fe3O4@Fe–N/HPCNF) displayed outstanding ORR activity with an onset potential of 0.99 V and a half-wave potential of 0.88 V in alkaline media, even comparable to that of commercial Pt/C. Additionally, Fe3O4@Fe–N/HPCNF catalyst also revealed excellent ORR performance with a half-wave potential of 0.75 V in acidic solution. More importantly, the optimal power density of Fe3O4@Fe–N/HPCNF assembled Zn-air battery can achieve 116 mW cm−2. The excellent electrocatalytic performance is benefited from the synergistic coupling between unique hierarchically porous carbon nanofibers and highly accessible Fe-based active sites.

CoN/MoC embedded in nitrogen-doped multi-channel carbon nanofibers as an efficient acidic and alkaline hydrogen evolution reaction electrocatalysts

Electrochemical water splitting has been extensively studied as a promising method for the production of clean and sustainable hydrogen fuels. However, the lack of low-cost and high-performance electrocatalysts for hydrogen evolution reaction (HER) has hindered their large-scale applications. Herein, one-dimensional (1D) CoN and MoC nanoparticles embedded in N-doped multi-channel carbon nanofibers (CoN/MoC/NMCNFs) are constructed by electrospinning technology coupled with carbonization process. The electronic structure of MoC is optimized by the interaction between CoN and MoC to improve the intrinsic activity of MoC. Owing to their excellent intrinsic activity, multi-channel structure, abundant active sites, and inhibitory effect of carbon on nanoparticles; CoN/MoC/NMCNFs exhibit excellent electrocatalytic performances in both acidic and alkaline environments, only 199.2 mV and 92.5 mV are respectively required to drive a current density of 10 mA cm−2. The average diameter and the specific surface areas of CoN/MoC/NMCNFs are 1.1 μm and 13.7 mg m−2, respectively. The catalytic activity of CoN/MoC/NMCNFs does not significantly change after 1000 and 2000 cycles of CV curve tests under alkaline and acid electrolysis conditions, respectively. This work provides a new idea for synthesis of simple, efficient, low-cost and non-Pt-based electrocatalysts.

A coactive performance of Ag2WO4 nanorods wreathed on the N-doped carbon nanofibers as electrode for electrochemical supercapacitors

The thriving energy demand of the gradually increasing population and modernised life style requires development in energy storage devices for usage in commercial electronic devices. In this particular work, we have explored electrochemical performances of bimetallic oxide Ag2WO4 nanorods and tuned its performance by decorating it on the nitrogen doped carbon nanofiber (N-CNF). The Ag2WO4 nanorods are synthesised by a facile route of co-precipitation method followed by ultrasonication with N-CNF. The synthesised Ag2WO4 nanorods was found electrochemically active and the incorporation of N-CNF end up boosting its electrochemical performances. The obtained nanocomposites were characterised by various advanced techniques. The amount of N-CNF was determined by characterisation via the potentiostatic and galvanostatic cycle measurements and electrochemical impedance spectroscopy (EIS). The electrochemically active Ag2WO4 with 20 wt. % of N-CNF (Ag2WO4/N-CNFb) exhibited 2.2-fold higher charge storage capacity than pristine Ag2WO4. The Ag2WO4/N-CNFb exhibited specific capacitance as high as 330 F g-1 at a constant applied current density of 1 A g-1 in 1 M KOH. The improved capacity may be due to conductive pathways provided by N-CNF. The Ag2WO4 got well decorated over the N-CNF facilitating the active sites interaction with electrolyte. The symmetric device fabricated with Ag2WO4/N-CNFb electrodes exhibited excellent energy density of 10 W h kg-1 at 6000 W kg-1 at 5 A g-1. The Ag2WO4/N-CNFb electrode long-term stability has been minutely observed; the high Coulombic efficiency of 90% and high rate of capacity retention 98% even after 3000 cycles. Owing to these excellent electrochemical properties, the research work can potentially widen the opportunity to explore other profound bimetallic oxides and its nanocomposites with conductive carbon-based matrix for energy storage applications.

Accelerated polysulfide conversion using nitrogen-doped carbon nanofibers embedded with V2O3 as interlayers for lithium-sulfur batteries

Accelerated polysulfide conversion using nitrogen-doped carbon nanofibers embedded with V2O3 as interlayers for lithium-sulfur batteries

Carbon nanofibers enabling manganese oxide cathode superior low temperature performance for aqueous zinc-ion batteries

Mn-based aqueous zinc-ion batteries are potential candidates for energy storage owing to the low cost, high efficiency, and safety. Nevertheless, the Jahn–Teller effect induces Mn2+ dissolution and irreversible phase changes, seriously deteriorating the cycling life. Herein, the facile construction and low temperature performance of the core–shell composites of polyimide derived nitrogen-doped carbon nanofibers and δ-MnO2 (δ-MnO2-CNFs) are reported, where ultrafine MnO2 arrays are tightly anchored on carbon nanofibers. The hybrid effect of nitrogen doping, porous structure, and abundant active sites effectively inhibits the structural damage of MnO2. The as-prepared δ-MnO2-CNFs cathode achieves a high specific capacity of 232.9 mAh g−1 and energy density of 450.7 Wh kg−1 at a current density of 100 mA g−1, and could be stably cycled for 500 cycles at a high current rate of 1 A g−1. The density functional theory calculation results show that the synergistic effect in δ-MnO2-CNFs is more conducive to the transfer of zinc ions. Furthermore, a salty ice electrolyte Zn(ClO4)2 has been used for the Zn//δ-MnO2-CNFs cell, which can work at a low temperature of −20 °C, and a stable low temperature (0 °C) cycle of 500 cycles is achieved at 1 A g−1.

Rational synthesis of chitin-derived nitrogen-doped porous carbon nanofibers for efficient polysulfide confinement

Rational synthesis of chitin-derived nitrogen-doped porous carbon nanofibers for efficient polysulfide confinement

Geometric and Electronic Structural Engineering of Isolated Ni Single Atoms for a Highly Efficient CO2 Electroreduction.

Tuning the coordination environment and geometric structures of single atom catalysts is an effective approach for regulating the reaction mechanism and maximize the catalytic efficiency of single-atom centers. Here, a template-based synthesis strategy is proposed for the synthesis of high-density NiNx sites anchored on the surface of hierarchically porous nitrogen-doped carbon nanofibers (Ni-HPNCFs) with different coordination environments. First-principles calculations and advanced characterization techniques demonstrate that the single Ni atom is strongly coordinated with both pyrrolic and pyridinic N dopants, and that the predominant sites are stabilized by NiN3 sites. This dual engineering strategy increases the number of active sites and utilization efficiency of each single atom as well as boosts the intrinsic activity of each active site on a single-atom scale. Notably, the Ni-HPNCF catalyst achieves a high CO Faradaic efficiency (FECO ) of 97% at a potential of -0.7V, a high CO partial current density (jCO ) of 49.6mA cm-2 (-1.0V), and a remarkable turnover frequency of 24900 h-1 (-1.0V) for CO2 reduction reactions (CO2 RR). Density functional theory calculations show that compared to pyridinic-type NiNx , the pyrrolic-type NiN3 moieties display a superior CO2 RR activity over hydrogen evolution reactions, resulting in their superior catalytic activity and selectivity.

Nitrogen-Doping-Induced High-Performance Carbon Nanofiber Anodes for Potassium-Ion Storage

Due to the abundant supply of potassium, potassium-ion batteries (PIBs) are considered as a promising alternative battery system to lithium-ion batteries (LIBs). Carbonaceous materials are the preferred anode materials for these batteries. However, the electrochemical performance of carbonaceous anode materials is still unsatisfactory, hindering the development of PIBs. In this work, nitrogen-doped carbon nanofibers (N-CNFs) were synthesized by the calcination of bacterial cellulose with urea acting as a nitrogen source. When employed as an anode material for PIBs, the N-CNFs exhibit a stable specific capacity of 205 mA h g–1 at 0.2 C after 250 cycles and an outstanding rate capability of 149.7 mA h g–1 at 5.0 C. The N-doped structure can facilitate the K+ and electronic conductivity, which will effectively enhance electrochemical performance of the electrode. In addition, ex situ X-ray photoelectron spectroscopy and X-ray diffractometry pattern analyses illustrate the reversible insertion of K+ in the N-CNF electrode.

Metal-free nitrogen-doped porous carbon nanofiber catalyst for solar-Fenton-like system: Efficient, reusable and active catalyst over a wide range of pH

Water pollution is a growing environmental crisis caused by industrialization. In-situ production of reactive oxygen species (ROS) is one of the most promising strategies to challenge this problem. However, developing a robust and efficient catalyst that can operate in harsh conditions without generating secondary pollution and tackle the recycling difficulties of powder catalysts remains a challenge. In this study, a graphitized N-doped carbon nanofiber (CNF) catalyst was synthesized in a direct synthesis approach, which is more efficient in time and cost and suitable for industrial applications, by means of electrospinning and carbonization process. Zinc acetate and iron nitrate functioned as a template for porous structure generation and carbon graphitizing catalysts. The as-synthesized catalyst was used in the wide pH range. This was mainly due to: i) the high surface area (∼ 652 m2 g−1) and the micro-mesoporous structure, which have reduced the inner diffusion resistance and facilitated mass transport radically during the reaction. ii) The enhanced electron transfer kinetics through the long 1D CNF revealed by the cyclic voltammetry analysis. iii) The abundance of oxygen-containing function groups, graphitic-C pyridinic-N and graphitic-N active sites that facilitated the activation of H2O2 and the generation of the ROS responsible for the degradation of the organic pollutants. The catalysts’ 1D structure and lightweight enabled the catalyst recovery and reuse.

Design and Performance Enhancement of Cobalt-Encapsulated Nitrogen-Doped Carbon Nanofiber Electrocatalyst through Ionic Liquid Modification for Efficient Oxygen Reduction

The design of platinum-group-metal-free (PGM-free) electrocatalysts with appreciable activity and durability toward the oxygen reduction reaction (ORR) in acidic environments is a big challenge. Here, we report an efficient oxygen reduction activity of a Co-encapsulated nitrogen-doped carbon with nanofiber networks and its ionic liquid-modified interface in an acidic medium. The robust structure of the nanofibers embedded on a rigid framework derived from a zeolitic imidazole framework (ZIF-67) delivers promising activity and durability to the catalyst comparable to the state-of-the-art Pt/C. The ionic-liquid-modified catalyst shows a half-wave potential of 0.71 V vs RHE in oxygen-saturated 0.5 M H2SO4 along with activity reduction by only 11 mV (E1/2) after 5000 cycles of the accelerated durability test. The catalyst also retains 71% of its original current during the short-term durability test. Furthermore, the electron transfer number and H2O2 yield of the catalyst during the ORR approaches 3.88–3.90 and 5.9–4.8% in the potential range 0.4–0.7 V vs RHE. The ORR performance of the ionic-liquid-modified catalyst is superior among all ionic liquid-based non-PGM catalysts reported so far in acidic media.