N-doped Porous Carbon Nanofibers Research Articles

Hierarchical porous N-doped carbon fibers enable ultrafast electron and ion transport for Zn-ion storage at high mass loadings

Zinc-ion capacitors (ZICs) are a promising and safe energy storage system for portable electronics but usually limited by relatively low areal capacity and energy density. Although increasing the mass loading has been suggested, thick electrode layers and clogged pores unavoidably lead to sluggish electron transport and ion diffusion as well as “dead volume” of active materials. Herein, a millimeter-scale 3D thick-network electrode, composed of closely intertwined hierarchical porous N-doped and free-standing carbon nanofibers (HPNCFs), was fabricated via carbonization of nanoscale zeolitic imidazolate framework (ZIF-8) particles embedded in electrospun polyacrylonitrile (PAN) nanofibers. With fast electron/ion transport, large ion-accessible surface area and high utilization rate of active materials, the mass loading of the HPNCFs electrode can reach 48.67 mg cm−2 with a thickness of 4.46 mm. Moreover, the HPNCFs-based ZICs can yield a superior areal/gravimetric capacity of 4.13 F cm−2 /280 F g−1, superior rate capability up to 193.7 F g−1 even at 100 A g−1, high energy density of 99.6 Wh kg−1, and long-term stability for 40,000 cycles. The straightforward approach can provide an opportunity to prepare efficient thick electrodes that could be applied in electrocatalysis, energy storage/conversion, and other electrochemical energy-related techniques.

Reduced Graphene Oxide Modified Nitrogen-Doped Chitosan Carbon Fiber with Excellent Electromagnetic Wave Absorbing Performance.

Lightweight and low-cost one-dimensional carbon materials, especially biomass carbon fibers with multiple porous structures, have received wide attention in the field of electromagnetic wave absorption. In this paper, graphene-coated N-doped porous carbon nanofibers (PCNF) with excellent wave absorption properties were successfully synthesized via electrostatic spinning, electrostatic self-assembly, and high-temperature carbonization. The obtained results showed that the minimum reflection loss of the absorbing carbon fiber obtained under the carbonization condition of 800 °C is -51.047 dB, and the absorption bandwidth of reflection loss below -20 dB is 10.16 GHz. This work shows that carbonization temperature and filler content have a certain effect on the wave-absorbing properties of fiber, graphene with nanofiber, and the design and preparation of high-performance absorbing materials by combining the characteristics of graphene and nanofibers and multi-component coupling to provide new ideas for the research of absorbing materials.

Selenium and phosphide-doped hollow porous N-doped carbon nanobox-based electrospun N-doped carbon nanofibers toward electrochemical sensing of hydrogen peroxide

A new strategy for doping selenium and phosphide in hollow N-doped carbon nanobox (N-CNB)-based porous electrospun N-doped carbon nanofibers (CNFs) was developed.

Red phosphorus encapsulated in 3D N-doped porous carbon nanofibers: an enhanced sodium-ion battery anode material.

We report a sodium-ion battery anode design using red phosphorus encapsulated in nitrogen-doped porous carbon nanofibers that mitigates volume expansion and poor conductivity issues, enhancing battery performance. Density functional theory calculations suggest nitrogen doping promotes robust phosphorus interactions, and finite element analysis indicates the design controls volume expansion.

A frogspawn inspired twin Mo2C/Ni composite with a conductive fibrous network as a robust bifunctional catalyst for advanced anion exchange membrane electrolyzers.

Anion exchange membrane water electrolysis (AEMWE) is considered one of the most cost-effective methods for producing green hydrogen. However, the performance of AEMWE is still restrained by the slow reaction kinetics and poor ion/electron transport of catalysts. Herein, inspired by frogspawn, Mo2C nanoparticles coupled with Ni were in situ embedded into a N-doped porous carbon nanofiber network (Mo2C/NCNTs@Ni) by chemical crosslinking electrospinning combined with carbonization. The unique bionic structure can guarantee favorable overall structural flexibility and fast ion/electron transport kinetics. As a result of the robust hydrogen binding energy of Mo2C, as well as the synergistic impact between Ni and Mo2C nanoparticles and the conductive network resembling frogspawn, the catalyst developed demonstrates excellent performance in both the HER and OER. When employed as a bifunctional catalyst in water electrolysis, Mo2C/NCNTs@Ni delivers overpotentials of 155 mV and 320 mV at 10 mA cm-2 for the HER and OER, respectively. In addition, the Mo2C/NCNTs@Ni also displays excellent long-term durability during a continuous operation test under different currents for 50 h. The assembled AEMWE electrolyzers with Mo2C/NCNTs@Ni as both the anode and cathode can achieve a current density of 82.5 mA cm-2 at 1.99 V, indicating great potential for industrial water splitting. These results give an insight for the development of advanced bifunctional electrocatalysts for the next generation of green and efficient H2 production by water electrolysis.

Constructing Fe–N-doped porous carbon nanofibers for a pH-universal ORR and switchable, superior Zn–air batteries

Efficient pH-universal electrocatalysts composed of highly dispersive tiny Fe nanoparticle units in a carbon nanofiber network is reported. The as-assembled zinc–air batteries in alkaline and neutral electrolytes exhibit excellent overall performance.

N-doped porous carbon nanofibers derived from N-rich cross-linked polymer for high-performance supercapacitors

N-doped porous carbon nanofibers derived from N-rich cross-linked polymer for high-performance supercapacitors

Porous N-Doped Carbon Decorated with Atomically Dispersed Independent Dual Metal Sites from Energetic Zeolite Imidazolate Frameworks as Bidirectional Catalysts for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have ultrahigh theoretical specific capacity and energy density, which are considered to be very promising energy storage devices. However, the slow redox kinetics of polysulfides are the main reason for the rapid capacity decay of Li-S batteries. A reasonable electrocatalyst for the Li-S battery should reduce the reaction barrier and accelerate the reaction kinetics of the bidirectional catalytic conversion of lithium polysulfides (LiPSs), thereby reducing the cumulative concentration of LiPSs in the electrolyte. In this report, porous N-doped carbon nanofibers decorated with independent dual metal sites as catalysts for Li-S batteries were fabricated in one step using a fusion-foaming method. Experimental and theoretical analyses demonstrate that the synergistic effect of independent dual metal sites provides strong LiPS affinity, improved electronic conductivity, and enhanced redox kinetics of polysulfides. Therefore, the assembled Li-S battery exhibits high rate performance (discharge specific capacity of 771 mA h g-1 at 2C) and excellent cycle stability (capacity decay rate of 0.51% after 1000 cycles at 1C).

Rational design of N-doped porous biomass carbon nanofiber electrodes for flexible asymmetric supercapacitors with high-performance

Flexible supercapacitors have become a concern of flexible energy storage devices. In the process of exploring, the squid ink as N-doped biomass carbon was introduced to self-supporting flexible supercapacitors by electrospinning for the first time. By regulating the content of squid ink, the activation temperature, and the mass ratio of KOH-assisted activation, a N-doped porous biomass carbon@polyacrylonitrile (NPBC-1.5@PAN-800-2) with an ideal capacity and an excellent specific surface area (636.68 m2 g−1) was prepared. In addition, ZnO further optimized the capacity (422.7 F/g at 1 A g−1) and as an adhesive-free electrode for flexible asymmetric supercapacitor provided a relatively high specific capacitance, a satisfactory capacitance retention, and a wonderful energy density (48.01 Wh kg−1 at 1124.43 W kg−1). The capacitance was thought to originate from a suitable microporous structure, N-doped, and metal-derived pseudocapacitance propertie.

Constructing ultrafine Pt nanoparticles anchored on N-doped porous carbon nanofibers for efficient and stable oxygen reduction reaction

Constructing ultrafine Pt nanoparticles anchored on N-doped porous carbon nanofibers for efficient and stable oxygen reduction reaction

Encapsulation of cobalt prussian blue analogue-derived ultra-small CoP nanoparticles in electrospun N-doped porous carbon nanofibers as an efficient bifunctional electrocatalyst for water splitting

Transition metal phosphides have been considered as prospective bifunctional electrocatalysts for overall water splitting due to high activity and excellent stability. In this work, we report a facile strategy for synthesizing high-dispersion cobalt Prussian blue analogue-derived CoP nanoparticles that are decorated on N-doped electrospun porous carbon nanofibers (denoted as CoP@CNF). The CoP@CNF is obtained using electrospinning, subsequent carbonization, and phosphatization treatment. Due to the high conductivity, abundance of electrocatalytic active sites, and the synergistic effect between ultra-fine CoP nanoparticles and porous N-doped electrospun carbon nanofibers, the prepared CoP@CNF catalyst exhibits remarkable activity with low overpotentials (127 and 300 mV) at 10 mA cm−2, and small Tafel slopes (73.4 and 73.8 mV dec−1) for hydrogen evolution reaction and oxygen evolution reaction in alkaline electrolyte, respectively. A water electrolyzer cell fabricated by applying CoP@CNF as both anode and cathode catalysts needs 1.64 V to achieve 10 mA cm−2, and exhibits remarkably long-term stability. This work provides useful guidance for the preparation of bifunctional nanocomposite electrocatalysts and further extends the application of Prussian blue analogues in the field of energy conversion.

Coupling MnS and CoS Nanocrystals on Self-Supported Porous N-doped Carbon Nanofibers to Enhance Oxygen Electrocatalytic Performance for Flexible Zn-Air Batteries.

Seeking highly efficient, stable, and cost-effective bifunctional electrocatalysts of rechargeable Zn-air batteries (ZABs) is the top-priority for developing new generation portable electronic devices. For this, the rational and effective structural design, interface engineering, and electron recombination on electrocatalysts should be taken into account to reduce the reaction overpotential and expedite the kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Herein, we construct a MnCo-based metal organic framework-derived heterogeneous MnS-CoS nanocrystals, which are anchored on free-standing porous N-doped carbon fibers (PNCFs) by the in situ growth method and vulcanization process. Benefiting from the abundant vacancies and active sites, strong interfacial coupling as well as favorable conductivity, the MnS-CoS/PNCFs composite electrode delivers a mentionable oxygen electrocatalytic activity and stability with a half-wave potential of 0.81 V for ORR and an overpotential of 350 mV for OER in the alkaline medium. Of note, the flexible rechargeable ZAB using MnS-CoS/PNCFs as binder-free air cathode offers high power density of 86.7 mW cm-2, large specific capacity of 563 mA h g-1, and adapts to different bending degree of operation. In addition, the density functional theory calculation clarifies that the heterogeneous MnS-CoS nanocrystals reduces the reaction barrier and enhances the conductivity of the catalyst and the adsorption capacity of the intermediates during the ORR and OER process. This study opens up a new insight to the design of the self-supported air cathode for flexible electronic devices.

Novel porous CoS1.097@carbon nanofibers as flexible and binder-free anode material for sodium-ion batteries

Transition metal sulfides (TMSs) have received numerous attention as anode materials for sodium-ion batteries because of the high theoretical capacity. So far, the Na-storage performance of TMSs is still unsatisfactory due to the structural degeneration that induced by the volume change upon redox process. Herein, a novel flexible and binder-free anode material of porous CoS1.097@carbon nanofibers was facilely constructed by means of the electrospinning, carbonization and sulfidation processes. The porous CoS1.097@carbon nanofibers display unique structure with CoS1.097 nanoparticles confined into porous N-doped carbon nanofibers, and can provide sufficient active sites, high electrical conductivity, reduced ion diffusion distance, abundant ion migration pathways, desirable voids for alleviating the volume variation, and rigid structural stability for efficient Na-storage. In consequence, the flexible and binder-free electrode material delivers high initial discharge capacity, enhanced rate capability and long-term cycling life. Besides, intrinsic diffusion and electrochemical storage behavior of Na+ ions were emphatically disclosed. This work paves a facile route for the synthesis of flexible and binder-free TMSs-based anode materials, promoting the practical application of wearable sodium-ion batteries.

Core-shell Ppy@N-doped porous carbon nanofiber-based electrodes for high-property supercapacitors

Here, core-shell supercapacitor electrodes with high performance were prepared using electrospinning, carbonation, nitrogen-doping and chemical polymerization. The core of the electrode was a N-doped porous carbon nanofiber skeleton, its shell was a conductive polymer loaded on it. The effects of pore-forming agent content, N-doped amount, and polymerization temperature on the morphologies, structures and electrochemical performance of products in each stage were characterized, and the optimum parameters were obtained. As a freestanding electrode, the SC of core-shell composite reached 342.13 F g−1 at 1 A g−1, and its SC attenuation was only 4.6 % after 1000 cycles, indicating its good charge storage performance and cycle stability. Then a symmetric supercapacitor fabricated with the best electrode displayed an energy density of 3.10 Wh kg−1 at a power density of 50 W kg−1. Therefore, this paper proposed an effective method for developing multifunctional electrode materials of supercapacitors.

Porous nanofibers comprising VN nanodots and densified N-doped CNTs as redox-active interlayers for Li–S batteries

A synthesis strategy to obtain hierarchically porous N-doped carbon (P–N–C) nanofibers (NFs) comprising VN nanodots and highly densified-entangled N-doped CNTs (N-CNTs) was visualized. The unique redox-active nanostructure was applied as a multifunctional interlayer for highly stable Li–S batteries (LSBs). The P–N–C skeleton obtained via selective removal of amorphous carbon (AC) and polystyrene (PS) not only guarantees efficient electrolyte percolation but also facilitates rapid diffusion of charged species during charge-discharge processes. Moreover, the N-CNTs constituting the fiber matrix increase the overall conductivity of the framework. Besides, highly conductive vanadium nitride (VN) nanodots act as chemisorption sites for efficient lithium polysulfide capturing and prohibit their diffusion towards the anode through efficient catalytic conversion, thus improving the elemental S utilization. The Li–S cells utilizing P–N–C@VN/N-CNT NF as a multifunctional barrier resulted in decent rate capabilities (559 mA h g−1 at 2.0 C) and long-term cycling stabilities at low and high C-rates (432 mA h g−1 after the 400th cycle at 0.1 C and 290 mA h g−1 at the end of 600th cycle at 1.0 C). This is attributed to the combined synergistic effects of the P–N–C framework, N-CNT matrix, and polar VN nanodots.

Stabilizing High Density Cu Active Sites with ZrO2 Quantum Dots as Chemical Ligand in N-doped Porous Carbon Nanofibers for Efficient ORR.

The emerging transition metal-nitrogen-carbon (MNC) materials are considered as a promising oxygen reduction reaction (ORR) catalyst system to substitute expensive Pt/C catalysts due to their high surface area and potential high catalytic activity. However, MNC catalysts are easy to be attacked by the ORR byproducts that easily lead to the deactivation of metal active sites. Moreover, a high metal loading affects the mass transfer and stability, but a low loading delivers inferior catalytic activity. Here, a new strategy of designing ZrO2 quantum dots and N-complex as dual chemical ligands in N-doped bubble-like porous carbon nanofibers (N-BPCNFs) to stabilize copper (Cu) by forming CuZrO3-x /ZrO2 heterostructures and CuN ligands with a high loading of 40.5wt.% is reported. While the highly porous architecture design of N-BPCNFs builds a large solidelectrolytegas phase interface and promotes mass transfer. The preliminary results show that the half-wave potential of the catalyst reaches 0.856V, and only decreases 0.026V after 10 000 cycles, exhibiting excellent stability. The proposed strategy of stabilizing metal active sites with both heterostructures and CuN ligands is feasible and scalable for developing high metal loading ORR catalyst.

In-situ encapsulating ultrafine CoFe2O4 nanoparticle into porous N-doped carbon nanofiber membrane as self-standing anode for enhanced lithium storage performance

The ultrasmall CoFe2O4 nanoparticles in situ encapsulated in porous N-doped carbon nanofibers membranes (CFO@PNCFM) with different pore structures have been prepared by electrospinning and subsequent carbonization. When immediately used as self-standing anodes for lithium-ion batteries (LIBs), the optimized CFO@PNCFM exhibits superior lithium storage properties with high rate capability (476.5 mAh g−1 at 2 A g−1) and long stable cycle life (755.8 mAh g−1 at 100 mA g−1 after 200 cycles). The outstanding electrochemical performance may be mainly ascribed to the synergistic effect of special 3D conductive porous carbon nanofibers (PCNFs) network and ultrafine CoFe2O4 nanoparticles in energy storage, which can significantly enhance the utilization efficiency of electroactive materials and improve the charge-transport kinetics. Moreover, the CoFe2O4 nanoparticles bonded closely to PCNFs through strong metal-oxygen bridges, which promote the electron capture and transfer from PCNFs to CoFe2O4, and thus achieving fast electrochemical reaction kinetics. Meanwhile, the porous structure can not only alleviate the volume change during charge/discharge cycles, but also supply numerous active sites for lithium storage, resulting in a high reversible capacity as well as good cycle stability and rate performance.

Encapsulation of KTi2(PO4)3 nanoparticles in porous N-doped carbon nanofibers as a free-standing electrode for superior Na/K-storage performance

Herein, a self-supporting electrospinning film of porous N-doped carbon nanofibers impregnated with KTi2(PO4)3 nanoparticles (abbreviated as NF-KTP) is constructed. The free-standing NF-KTP exhibits excellent flexibility and is directly adopted as a binder-free anode for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs). The introduction of conductive N-doped carbon matrix enables enhanced intrinsic electronic conductivity and fast ion diffusion kinetics, as well as the fabrication of porous nitrogen-doped interconnected carbon fibers impregnated with KTi2(PO4)3 nanoparticles can offer a short transport path of sodium/potassium ions and buffer the volume expansion during repetitive intercalation/deintercalation. Therefore, the NF-KTP electrode delivers an initial charge capacity of 116.8 mAh g−1 at 0.2 C, superb rate capability of 107.8 mAh g−1 at 50 C and impressive cycling stability with a capacity retention of 92.8 % for 1000 cycles at 5 C in SIBs. Even at 0 °C and 50 °C, it still retains marvelous rate performance with capacities of 99.8 and 106.3 mAh g−1 at 50 C, respectively. Meanwhile, as an anode material for PIBs, NF-KTP also displays good electrochemical performances, as reflected by its exceptional rate performance (99.3 mA h g−1 at 10 C) and superb cycling performance (with no capacity fading after 300 cycles at 5 C). These satisfactory electrochemical properties can be ascribed to the superiority of the stable 3D network formed by KTP nanofibers. Such a simple and effective strategy may provide a new vision for other materials applied in energy storage systems.

Robust N-doping porous carbon nanofiber membranes with inter-fiber cross-linked structures for supercapacitors

Enhancing the electrochemical performance while maintaining excellent mechanical properties of carbon nanofiber-based flexible electrodes remains a significant challenge, which blocks their potential application in advanced energy storage and conversion. Herein, taking advantage of the thermal stability difference between polyacrylonitrile and polypyrrolidone, we report a simple strategy to fabricate N-doped porous carbon nanofiber membranes with inter-fiber cross-linked structures via eccentric coaxial electrospinning combined with carbonization processes. During carbonization processes, the obstacles of large contact resistance are removed and sufficient contacts among electrospun nanofibers are formed, endowing the carbon nanofiber membranes with outstanding electrical conductivity (25.4 S cm−1) and flexibility in various forms. Further, NiCo2O4 nanoneedles are in-situ decorated onto the prepared carbon nanofiber membranes to construct hybrid electrodes for improving capacitance. The hybrid electrodes (NiCo2O4@NPCNFs) achieve a competitive specific capacitance (capacity) of 1474.2 F g−1 (245.4 mAh g−1) at the current density of 0.5 A g−1, as well as good rate performance (78.0% capacitance retention at a current density of 10 A g−1). In addition, the assembled asymmetric supercapacitors exhibit a high energy density of 53.0 Wh kg−1. This study paves a promising way toward carbon nanofiber-based electrodes for application in energy storage systems.

Preparation of N-doped porous carbon nanofibers derived from their phenolic-resin-based analogues for high performance supercapacitor

• N-doped porous carbon nanofibers are synthesized via a simple hydrothermal method. • Carbon nanofibers are derived from their phenolic-resin-based analogues. • The mechanism underlying is proposed in the viewpoint of micelle evolvement. • N-doped carbon as electrode material offers superior electrochemical performance. Carbon nanofibers (CNFs), possessing high electrical conductance and facilitating fast electron transfer due to 1D structure, attract more research interests in the field of energy storage/conversion. It is highly desirable to develop a simple synthetic approach to prepare high quality CNFs for high efficient electrode material. Herein, a facile method is developed to prepare nitrogen-doped porous CNFs with high aspect ratio by direct pyrolysis of phenolic-resin-based precursors which are synthesized via a simple hydrothermal approach. After activation by KOH, the nitrogen-doped porous CNFs demonstrate a high surface area up to 1814.1 m 2 /g thereby offering a high capacitance while working as the electrode material assembled in a supercapacitor. The activated CNFs as electrode material present a high specific capacitance of 333.5F g −1 at a current density of 0.5 A g −1 in a three-electrode cell. After 10,000 cycles of charge–discharge tests at 5A g −1 , the decay in specific capacitance is only 3.7 %, indicating a high reversibility. Also, the tests in a two electrode system show a high energy density of 8.6 Wh kg −1 at a power density of 25 W kg −1 . Therefore, the nitrogen-doped CNFs derived from its phenolic-resin-based precursor hold a promise for an efficient electrode material in supercapacitor.