Nitrogen-doped Carbon Nanofibers Research Articles

Nanofiber-Based Oxygen Reduction Electrocatalysts with Improved Mass Transfer Kinetics in a Meso-Porous Structure and Enhanced Reaction Kinetics by Confined Fe and Fe3C Particles for Anion-Exchange Membrane Fuel Cells

The development of high-performance nonprecious metal catalysts for oxygen reduction reactions is critical for the commercialization of fuel cells. In this paper, we report a non-precious catalyst with high-performance, in which Fe and Fe3C is embedded in nitrogen-doped carbon nanofibers (MIL-N-CNFs) by co-electrospinning Fe-MIL and polyacrylonitrile (PAN) and pyrolyzing. The mass ratio of Fe-MIL to PAN in the precursors and the pyrolysis temperature were optimized to be 1.5 and treated at 800 °C, respectively. The optimized catalyst exhibited an onset potential of 0.950 V and a half-wave potential of 0.830 V in alkaline electrolytes, thanks to the improved mass transfer kinetics in a meso-porous structure and enhanced reaction kinetics by confined Fe and Fe3C particles. Additionally, the optimized catalyst showed a better methanol tolerance than the commercial 20 wt.% Pt/C, indicating a potential application in direct methanol fuel cells. Serving as the cathode in CCM, the anion-exchange membrane fuel cell reaches a power density of 192 mW cm−2 at 428 mA cm−2 and 80 °C.

Self-supported hierarchically porous 3D carbon nanofiber network comprising Ni/Co/NiCo2O4 nanocrystals and hollow N-doped C nanocages as sulfur host for highly reversible Li–S batteries

Hierarchically porous nitrogen-doped carbon nanofibers (P-N-CNF) comprise well-embedded metallic-Ni/Co and spinel-type NiCo2O4 nanocrystals (Ni-Co/NiCo2O4) along with metal-organic framework-derived hollow nitrogen-doped carbon nanocages (HNC), denoted as P-N-CNF@NCO/HNC, are rationally designed as cathode substrates for advanced lithium-sulfur batteries with feasible parameters. The highly conductive and porous N-CNF matrix provides numerous conductive channels for rapid ionic and electronic transfer. HNC guarantees efficient impregnation of a large volume of active material along with high loading, channelizing the volume variation stress, and ensuring efficient electrolyte percolation, which is crucial for uniform dispersion and high active sulfur utilization, especially at low electrolyte/sulfur (E/S) ratios. The metallic-Ni/Co and polar spinel-type NiCo2O4 nanoparticles offer sufficient chemisorption sites to prevent polysulfide migration towards the anode. Li-S cells assembled using P-N-CNF@NCO/HNC as an advanced host and lithium polysulfide catholyte as the starting material displayed stable electrochemical performance even with strident battery parameters, including high sulfur content (79.8 wt%), high sulfur loading (7.7 mg cm−2), and low E/S ratio (8.0 µL mg−1). The cell displays a maximum areal capacity of 5.4 mA h cm−2 that stabilizes to 2.8 mA h cm−2 after 160 cycles at 0.1 C and is comparable to the theoretical threshold of presently available commercial systems.

Electrospun N-S-Codoped Carbon Nanofibers As Metal-Free Electrocatalysts With Catalytic Activity For The Oxygen Reduction Reaction In Alkaline Media

In this work, we have developed metal-free electrocatalysts based on sulfur and/or nitrogen-doped carbon nanofibers (CNFs) by in situ electrospun doping method. Heteroatom-doped CNFs have diameter ≈ 350 nm and nitrogen and sulfur species on their surface. Moreover, the catalytic activity for the oxygen reduction reaction (ORR) is evaluated in alkaline electrolyte (0.5M KOH). The most active metal-free electrocatalyst labelled as S-CNF has an onset potential of 0.817 V vs. RHE, HO2 - % yield of ≈12-15% and n = 3.7 and high ethanol tolerance. The Accelerated Degradation Test (ADT) show that S-CNF catalytic activity decrease only 13% evaluated at a potential range of 0.6 to 1.0 V vs. RHE. Furthermore, S-CNF even is evaluated by ADT as support (1.0 to 1.6 V/RHE, 6000 cycles) showing high long-term stability decreasing only 11% its catalytic activity. These results indicate N-S-codoped CNFs are a promising and eco-friendly alternative for fuel cells applications.

Fluorinated bimetallic nanoparticles decorated carbon nanofibers as highly active and durable oxygen electrocatalyst for fuel cells

The low activity and durability are still the critical barriers for non-precious metal electrocatalyst, mainly involving M-N/C (M = Fe, Co, Mn et al), applied in fuel cell. Constructing bimetallic sites has been explored as an effective method to boost the performance of the catalyst for the synergistic effect between metal atoms. However, this synergistic effect is always suppressed in acidic conditions and results in unstable catalytic performance. Here we create novel fluorinated iron (Fe) and cobalt (Co) bimetallic nanoparticles distributed on nitrogen-doped carbon nanofibers (CNFs) for oxygen reduction reaction (ORR). The fluorination strongly increased the charge density of the bimetallic catalyst and resulted in a remarkable catalytic performance with the half-wave potential of 804 mV in 0.1 M HClO4 and 1.6 times power density improvement for the proton exchange membrane fuel cell device. Importantly, the chemical and mechanical robust CNFs support improved the electric conductivity and stability of bimetallic catalysts, which leads to an ultra-stable electrocatalyst. The fuel cell voltage can keep stable even after 110 h, instead of the continuingly decrease in the traditional M-N/C.

Hollow nitrogen-doped carbon nanofibers filled with MnO2 nanoparticles/nanosheets as high-performance microwave absorbing materials

The nitrogen-doped carbon nanofiber absorber (MnO2@HNCFs) filled with MnO2 nanoparticles/nanosheets is constructed through layer-by-layer coating assisted by vacuum carbonization and etching. The MnO2 nanoparticles/nanosheets filled in the hollow carbon fibers make the material exhibit a hierarchical porous structure, and reduce the density of the material as well. MnO2@HNCFs show excellent microwave absorbing properties, with a minimum reflection loss (RLmin) of −48.87 dB@14.9 GHz at a low loading of 10%, and the thickness is 2.5 mm. The corresponding effective absorption bandwidth (EAB) is 6.2 GHz, covering the entire Ku-band. When the thickness is adjusted to 2.8 mm, the EAB is up to 7.8 GHz and the RLmin is −32.17 dB. The EAB is 5.7 GHz at 3.4 mm, covering the X-band, and the RLmin is −30.62 dB. Through the comparison of the absorbing properties of materials, it is proved that the construction of porous structures can effectively enhance the absorbing properties, which provides a solid argument for the claim that multiple reflection can enhance the electromagnetic wave loss. This work is of great significance to the construction of porous structure microwave absorbing materials, and provides a new idea for the design of lightweight microwave absorbing materials.

Synergistic Effect of WN/Mo2C Embedded in Bioderived Carbon Nanofibers: A Rational Design of a Shuttle Inhibitor and an Electrocatalyst for Lithium-Sulfur Batteries.

To improve the innate shuttle effect and the sluggish redox kinetics of lithium-sulfur batteries, a composite made of a bimetallic compound embedded in nitrogen-doped carbon nanofibers (CNFs) is synthesized by employing biomass collagen fibers (CFs) as a structure template. Metal anions WO42- and MoO42- are grafted on plant polyphenol-modified CFs and then in situ converted into WN/Mo2C implanted in a matrix of CNFs (WMCNFs). The obtained WN/Mo2C is of quantum size and uniform distribution, exposing the active sites maximally. Further, the heterostructure of the bimetallic composite enables unique electronic interaction, thereby synergistically enhancing its adsorption capability toward soluble intermediates and activating its catalytic function for liquid-liquid and liquid-solid conversions. Combining these merits, when used as a separator modification material and a sulfur host simultaneously, the WMCNFs composite exhibits remarkable cycling stability with 91.45% capacity retention after 500 cycles at 2 C and also prominent rate performance of delivering 552.75 mAh g-1 at a current rate of 10 C. Meanwhile, the stable luminescence operation of LED lights powered by the assembled pouch cell demonstrates the application potential of this biomaterial-derived composite.

Self-supporting nitrogen-doped reduced graphene oxide@carbon nanofiber hybrid membranes as high-performance integrated air cathodes in microbial fuel cells

The traditional air cathode in microbial fuel cell (MFC) usually consists of catalyst layer (CL), supporting layer (SL) and conductive gas diffusion layer (GDL), the overall MFC performance is inevitably affected by the additional and expensive adhesives and conductive agents. Here, we developed an integrated air cathode in MFC without any additional SL, GDL or adhesives. The integrated air cathode was self-supporting nitrogen-doped reduced graphene oxide@carbon nanofiber (N-rGO@CNF) hybrid membranes fabricated by electrospinning with subsequent heat-treatment under ammonia atmosphere. The as-fabricated N-rGO@CNFs possessed far superior MFC performance and oxygen reduction reaction (ORR) activity to the pristine nitrogen-doped carbon nanofibers (NCNF) and commercial activated carbon (CAC). The amount of rGO embedded into CNF had prominent influence on their ORR activities and MFC performances. N-5-rGO@CNF had the lowest resistance and the maximal exchange current density, exhibiting desirable oxygen reduction performance via a four-electron pathway. The maximum power density of N-5-rGO@CNF can reach 826 mW m−2 in MFC, which is approximately 9, 2.53 and 1.82 times of pristine NCNF, CAC and Pt/C with values of 91, 327 and 454 mW m−2. The outstanding performance of the integrated air-cathodes originates from the integrality, brevity and hybrid composition of the electrospun nanofiber membrane. The appropriate embedded rGO not only improves the bulk conductivity of the rGO@CNF to promote ion adsorption, but also provides vacancies to accommodate ions, the doped nitrogen atoms facilitate O2 adsorption and/or subsequent O–O bond breaking, thus improving the electrochemical performance of N-rGO@CNF in MFC.

Multifunctional quasi-solid-state zinc-ion hybrid supercapacitors beyond state-of-the-art structural energy storage

Structural energy storage devices offer both electrochemical and mechanical performance in a single multifunctional platform, making them promising for weight- and/or volume-restricted applications such as electric vehicles, aircraft, and satellites. However, the development of state-of-the-art multifunctional energy storage is predominately hindered by poor energy density. Other parameters that influence the mechanical and electrochemical properties are also neglected, such as temperature, safety, etc. Herein, we assembled the first freeze-resistant, multifunctional quasi-solid-state zinc-ion hybrid supercapacitor (ZIHSC) using mechanically-strong hot-drawn, highly-porous nitrogen-doped carbon nanofibers as the load-bearing cathode and zinc foil as a paintable, malleable, low cost, highly safe, and robust anode. Considering the novel “two-birds-one-stone” strategy, the as-prepared multifunctional ZIHSCs outperform state-of-the-art structural energy storage devices in terms of a combination of energy storage and load-bearing capability. The structural ZIHSCs offer a battery-level gravimetric energy density of 113.1 Wh/kg, areal energy density of 300.0 μWh/cm2, strength of 308 MPa, Young's modulus of 14.40 GPa, toughness of 1.82 MJ/m3, and cycling stability over 7500 cycles. In addition, multifunctional ZIHSCs offer outstanding electrochemical and mechanical performance under a wide range of temperatures from cryogenic (−25 °C) to ambient (+25 °C) conditions.

Rationally designed hierarchical tree-like Fe-Co-P@Ni(OH)2 hybrid nanoarrays for high energy density asymmetric supercapacitors

Transition metal phosphides (TMPs) are regarded as promising materials for supercapacitors (SCs) owing to their excellent redox activity and electrical conductivity. However, their inferior rate performance and poor long-term cycling stability hinder their real-world applications. Engineering nanostructured multicomponent TM-based hybrid materials with rational core@shell architectures is a promising approach to prepare advanced electrodes for SCs. Herein, hierarchical Fe-Co-P@Ni(OH)2 core@shell nanoarrays assembled from needle-type Fe-Co-P nanoarrays and ultrathin Ni(OH)2 nanosheets have been grown vertically on Ni-foam via a successive hydrothermal reaction, phosphorization, and chemical bath deposition method. The as-fabricated Fe-Co-P@Ni(OH)2 electrode exhibits an ultra-high specific capacity of 380.61 mA h g−1 at 5 mA cm−2, high rate capability (61% at 50 mA cm−2) and retains 90% of its capacity after 5000 galvanostatic charge/discharge cycles. Moreover, an asymmetric supercapacitor device was assembled by integrating Fe-Co-P@Ni(OH)2 (positive) and polyacrylonitrile-derived nitrogen doped carbon nanofiber (negative) electrodes, which delivers a high energy density of 65.09 W h kg−1 at a power density of 530.06 W kg−1, outstanding rate capability (54% at 80 mA cm−2), and excellent cycling performance.

Nitrogen-doped carbon nanofibers derived from phenolic-resin-based analogues for high-performance lithium-ion batteries

The preparation of one-dimensional (1-D) carbon nanofibers (CNFs) for lithium-ion battery (LIB) anode materials plays a crucial role in electrochemical energy storage, but it still remains a great challenge due to the limited synthesis methods. Herein, we use a facile strategy to prepare the nitrogen-doped porous CNFs with high aspect ratio by direct pyrolysis of their phenolic-resin-based precursors in ammonium atmosphere. The polymer precursors are synthesized via a hydrothermal approach and have very high carbon yield over 50% in mass. Benefited from the unique 1-D porous structure, high nitrogen content and good conductivity, the ammonium-treated N-doped porous CNFs demonstrate an outstanding electrochemical lithium storage performance. The as-prepared N-doped porous CNFs demonstrates a high irreversible capacity of 325.2 mA h g−1 at 1000 mA g−1 together with an excellent long cycling performance (485.1 mA h g−1 at 500 mA g−1) after 500 cycles. This work offers a facile preparation strategy of the N-doped porous CNFs for high-efficiency energy storage electrode materials.

Valence Engineering of Polyvalent Cobalt Encapsulated in a Carbon Nanofiber as an Efficient Trifunctional Electrocatalyst for the Zn-Air Battery and Overall Water Splitting.

The rapid development of electrochemical power systems has prompted high demand for nonprecious trifunctional electrocatalysts with superior performance, prolonged stability, and low cost for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). Here, a valence engineering strategy is devised to construct a morphology with polyvalent cobalt encapsulated in nitrogen-doped carbon nanofibers (Co/N-CNFs). The diverse cobalt valence states of the Co/N-CNF catalysts contribute to their excellent catalytic effect and high durability in multiple electrochemical processes. The optimal Co/N-CNF catalyst fabricated exhibits a high half-wave potential of ORR (0.86 V) and low overpotentials of OER (380 mV) and HER (241 mV) at 10 mA cm-2. The Co/N-CNF-based Zn-air battery possesses a high charge-discharge efficiency as well as a good cycle stability (50 h at 10 mA cm-2 and 120 h at 20 mA cm-2), much superior to the Pt/C-based batteries. Furthermore, the Co/N-CNF catalyst could perform efficient overall water splitting.

Heterostructural Snse/Snte Ultrasmall Nanoparticles Embedded in Nitrogen-Doped Carbon Nanofibers (Snse/Snte@N-Cnfs) for High Performance Sodium-Ion Batteries

Heterostructural Snse/Snte Ultrasmall Nanoparticles Embedded in Nitrogen-Doped Carbon Nanofibers (Snse/Snte@N-Cnfs) for High Performance Sodium-Ion Batteries

Nitrogen-Doped Porous Carbon Nanofiber Decorated with Feni Alloy for Dendrite-Free High-Performance Lithium Metal Anode

Nitrogen-Doped Porous Carbon Nanofiber Decorated with Feni Alloy for Dendrite-Free High-Performance Lithium Metal Anode

Efficient ambient ammonia synthesis by Lewis acid pair over cobalt single atom catalyst with suppressed proton reduction

A Lewis acid pair over a single Co atom anchored on sponge-like nitrogen-doped mesoporous hollow carbon nanofibers was designed. The catalyst exhibits an NH3 production rate of 67.6 μg h−1 mg−1 and a maximum Faraday efficiency of 56.9% at a peak potential of −0.1 V vs. RHE.

FeCoS2 polyhedral spherical nanoparticle decorated nitrogen doped hollow carbon nanofibers as high-performance self-supporting anodes for K-ion storage.

Herein, we present a freestanding and flexible 3D nanocomposite made of polyhedral spherical FeCoS2 and nitrogen-doped hollow carbon nanofibers (FeCoS2@N-HCNFs) that is synthesized through coaxial electrospinning, high-temperature calcination, and a facile solvothermal process. As a binder-free anode composite for potassium-ion batteries (PIBs), FeCoS2@N-HCNF presents a high specific discharge capacity on the first lap (701.2 mA h g-1 at 100 mA g-1) and superior cycling stability (132.6 mA h g-1 at 3200 mA g-1 after 600 cycles). The impressive electrochemical performance can be ascribed to the unique 3D structure, such as the enormous specific surface area of the mesoporous structure beneficial for K+ transfer, the three-dimensional hollow carbon nanofiber scaffold enhances the structural stability, and polyhedral spherical FeCoS2 improves the overall specific capacity. According to the above description, the FeCoS2@N-HCNF anode is a promising candidate for advanced potassium-ion batteries.

Enhanced stability of nitrogen doped porous carbon fiber on cathode materials for high performance lithium-sulfur batteries.

Lithium–sulfur (Li–S) batteries are considered to be one of the candidates for high-energy density storage systems due to their ultra-high theoretical specific capacity of 1675 mA h g−1. However, problems of rapid capacity decay, sharp expansion in volume of the active material, and the shuttle effect have severely restricted their subsequent development and utilization. Herein, we design a nitrogen-doped porous carbon nanofiber (NPCNF) network as a sulfur host by the template method. The NPCNF shows a feather-like structure. After loading sulfur, the NPCNF/S composite can maintain a hierarchically porous structure. A high discharge capacity of 1301 mA h g−1 is delivered for the NPCNT/S composite at 0.1C. The reversible charge/discharge capacity at 2C is 576 mA h g−1, and 700 mA h g−1 is maintained after 500 cycles at 0.5C. The high electrochemical performance of this NPCNT/S composite is attributed to the synergy effects of abundant N active sites and high electrical conductivity of the material.

Metal-Free Nitrogen-Doped Porous Carbon Nanofiber Catalyst for Solar-Fenton-Like System: Efficient, Reusable and Active Catalyst Over a Wide Range of Ph

Metal-Free Nitrogen-Doped Porous Carbon Nanofiber Catalyst for Solar-Fenton-Like System: Efficient, Reusable and Active Catalyst Over a Wide Range of Ph

Nitrogen-Doped Porous Carbon Nanofiber Decorated with Feni Alloy for Dendrite-Free High-Performance Lithium Metal Anode

Nitrogen-Doped Porous Carbon Nanofiber Decorated with Feni Alloy for Dendrite-Free High-Performance Lithium Metal Anode

Construction of Cos-Encapsulated in Ultrahigh Nitrogen Doped Carbon Nanofibers from Energetic Metal-Organic Frameworks for Superior Sodium Storage

Construction of Cos-Encapsulated in Ultrahigh Nitrogen Doped Carbon Nanofibers from Energetic Metal-Organic Frameworks for Superior Sodium Storage

WITHDRAWN: Petal-like NiCoP sheets on 3D nitrogen-doped carbon nanofiber network as a robust bifunctional electrocatalyst for water splitting

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