Nitrogen-doped Carbon Nanofibers Research Articles

Electrospun Co-MoC Nanoparticles Embedded in Carbon Nanofibers for Highly Efficient pH-Universal Hydrogen Evolution Reaction and Alkaline Overall Water Splitting.

The construction of highly efficient and self-supported electrocatalysts with abundant active sites for pH-universal hydrogen evolution reaction (HER) and alkaline water splitting is significantly challenging. Herein, Co and MoC nanoparticles embedded in nitrogen-doped carbon nanofibers (Co-MoC/NCNFs) which display a bamboo-like morphology are prepared by electrospinning followed by the carbonization method. The electrospun MoC possesses an ultrasmall size (≈5nm) which can provide more active sites during electrocatalysis, while the introduction of Co greatly optimizes the electronic structure of MoC. Both endow the Co-MoC/NCNFs with superior HER performances over a wide pH range, with low overpotentials of 86, 116, and 145mV to achieve a current density of 10mAcm-2 in alkaline, acidic, and neutral media, respectively. Additionally, the catalyst exhibits remarkable alkaline oxygen evolution reaction (OER) activity with an overpotential of 254mV to reach 10mAcm-2. Density functional theory calculations confirm that electron transfer from Co to MoC regulates the adsorption free energy for hydrogen, thereby promoting HER. Moreover, an electrolyzer assembled with Co-MoC/NCNFs requires only a cell voltage of 1.59V at 10mAcm-2 in 1m KOH. This work opens new pathways for the design of high-efficiency electrocatalysts for energy conversion applications.

D-Electrons of Platinum Alloy Steering CO Pathway for Low-charge Potential Li-CO2 Batteries.

Aprotic Li-CO2 batteries suffer from sluggish solid-solid co-oxidation kinetics of C and Li2CO3, requiring extremely high charging potentials and leading to serious side reactions and poor energy efficiency. Herein, we introduce a novel approach to address these challenges by modulating the reaction pathway with tailored Pt d-electrons and develop an aprotic Li-CO2 battery with CO and Li2CO3 as the main discharge products. Note that the gas-solid co-oxidation reaction between CO and Li2CO3 is both kinetically and thermodynamically more favorable. Consequently, the Li-CO2 batteries with CoPt alloy-supported on nitrogen-doped carbon nanofiber (CoPt@NCNF) cathode exhibit a charging potential of 2.89 V at 50 µA cm-2, which is the lowest charging potential to date. Moreover, the CoPt@NCNF cathode also shows exceptional cycling stability (218 cycles at 50 µA cm-2) and high energy efficiency up to 74.6%. Comprehensive experiments and theoretical calculations reveal that the lowered d-band center of CoPt alloy effectively promotes CO desorption and inhibits further CO reduction to C. This work provides promising insights into developing efficient and CO-selective Li-CO2 batteries.

Ultrafine Fe-Mn bimetallic nanoparticles anchored in nitrogen-doped carbon nanofiber electro-Fenton membrane with strong metal-support interactions for sustainable water decontamination in wide pH ranges

Designing a membrane electrode with high activity and anti-scaling ability in a wide pH range is crucial to the development of flow-through electro-Fenton system. Herein, we reported a novel porous membrane composed of ultrafine FeMn bimetallic nanoparticles anchored in nitrogen-doped carbon nanofibers (FeMn/N-CNF) obtained through a facile electrospinning-carbonization process. The strong metal-support interaction (SMSI) phenomena including carbon encapsulation structure and electron transfer from metal to N-CNF, beneficial to the intrinsic activities, were successfully induced by the enhanced interfacial metal-nitrogen bonding in FeMn/N-CNF. Microstructural characterizations and leaching test revealed that the SMSI encapsulation structure could promote the formation of ultrafine FeMn nanoparticles in N-CNF during the high-temperature carbonization process and prevent leaching of active Fe/Mn metals into solution across a wide pH range. The constructed gravity-driven flow-through electro-Fenton system based on a FeMn/N-CNF cathode membrane exhibited superior performance to generate H2O2 (36.23 mmol L−1 h−1) and subsequent activate H2O2 decomposition to hydroxyl radicals (0.1024 min−1), achieving remarkable degradation efficiencies of 96.8%, 92.3%, and 90.3% within 60 min for Rhodamine B, Tetracycline, and Methyl Orange, respectively. Furthermore, the FeMn/N-CNF membrane filter demonstrated good pH adaptability, excellent cycle stability and anti-scaling ability during the degradation process. This work offers a viable avenue to enhance degradation performance and environmental robustness for practical water decontamination via achieving SMSI effect in carbon-supported electro-Fenton membranes.

Integrating Cu+/Cu0 sites on porous nitrogen-doped carbon nanofibers for stable and efficient CO2 electroreduction to multicarbon products

The Cu+/Cu0 sites of copper-based catalysts are crucial for enhancing the production of multicarbon (C2+) products from electrochemical CO2 reduction reaction (eCO2RR). However, the unstable Cu+ and insufficient Cu+/Cu0 active sites lead to their limited selectivity and stability for C2+ production. Herein, we embedded copper oxide (CuOx) particles into porous nitrogen-doped carbon nanofibers (CuOx@PCNF) by pyrolysis of the electrospun fiber film containing ZIF-8 and Cu2O particles. The porous nitrogen-doped carbon nanofibers protected and dispersed Cu+ species, and its microporous structure enhanced the interaction between CuOx and reactants during eCO2RR. The obtained CuOx@PCNF created more effective and stable Cu+/Cu0 active sites. It showed a high Faradaic efficiency of 62.5% for C2+ products in H-cell, which was 2 times higher than that of bare CuOx (∼31.1%). Furthermore, it achieved a maximum Faradaic efficiency of 80.7% for C2+ products in flow cell. In situ characterization and density functional theory (DFT) calculation confirmed that the N-doped carbon layer protected Cu+ from electrochemical reduction and lowered the energy barrier for the dimerization of *CO. Stable and exposed Cu+/Cu0 active sites enhanced the enrichment of *CO and promoted the C–C coupling reaction on the catalyst surface, which facilitated the formation of C2+ products.

Copper nanoparticles anchored on nitrogen-doped carbon nanofibers derived from MOFs and bacterial cellulose: Advanced electrocatalysts for oxygen reduction in microbial fuel cells

The development of efficient and inexpensive cathode catalysts contributes to energy conservation. Herein, nitrogen-doped carbon nanofiber (CNF) composites (Cu@N-CNFs) loaded with copper nanoparticles were successfully synthesized as cathode electrocatalysts for microbial fuel cells (MFCs), utilizing metal-organic frameworks (MOFs) and bacterial cellulose (BC) as precursors. The characterization results show that Cu@N-CNFs has a large specific surface area and contains catalytic active substances such as pyridine nitrogen and graphite nitrogen, along with that the graphitization degree of carbon skeleton structure is high. Therefore, Cu@N-CNFs has outstanding catalytic performance in alkaline and neutral environments, with half-wave potentials of 0.83 V and 0.78 V, as well as limiting current densities of −5.70 mA cm−2 and −5.73 mA cm−2, respectively. Moreover, these performances are comparable to those of Pt/C. The composite material is coated on the surface of the carbon cloth and processed into MFC cathode, which has a good improvement in its power production performance.

Electrospun metal-organic framework materials derived bimetallic oxides as high-efficiency anodes for lithium-ion battery

Energy devices are receiving more and more attention, and this is especially true for lithium-ion batteries. Moreover, applying novel nanostructures in multicomponent systems is a very effective way to promote the development of energy storage systems. This study synthesizes a nitrogen-doped carbon nanofiber encapsulating MOF-derived bimetallic oxide nanomaterial by combining electrospinning and MOF materials. Nitrogen-doped carbon nanofibers are porous and highly conductive, providing structural stability, a practical pathway for lithium ion diffusion, and an essential channel for rapid charge transfer during cycling. The bimetallic oxides derived from the MOF materials provide sufficient space for fast reaction sites and mitigate volume expansion during cycling. When the composite material FNO@NCNFs is used as the anode material for lithium batteries, its reversible capacity is maintained at 1105.4 mAh g−1 after 100 cycles at a current density of 0.1 A g−1. Its capacity reaches 748.5 mAh g−1 after 900 cycles at a current density of 1 A g−1, and at the same time, it exhibits excellent cycling stability, with the coulombic efficiency remaining above 98 %. The material also exhibits a small ion transfer resistance and good rate performance. The structural design approach based on combining MOFs with electrospinning in this study will provide new insights into the design and development of materials for advanced energy storage applications.

Effective oxygen evolution of NCF@CoNiO2 with one-dimensional core-shell structure synthesized by induced effect of polymer nanofibers

The non-noble bimetallic oxides have recently received more and more attention in electrocatalytic oxygen evolution reaction (OER) because of their potential to replace traditional precious metal catalysts, but the low activity and stability limit their wide application. Herein, the bimetallic oxide CoNiO2 layers are decorated on the nitrogen-doped carbon nanofibers (NCF) through in situ grown of Ni(Co) bimetal organic frameworks (Ni(Co)-MOFs) on polyacrylonitrile nanofibers and subsequent pyrolysis process, so that a new NCF@CoNiO2 electrocatalyst with one-dimensional (1D) core-shell structure is synthesized by structural induced effect of polyacrylonitrile nanofibers. Importantly, the unique interconnected network formed in the 1D NCF@CoNiO2 electrocatalyst effectively improves electron mobility and mass transport capacity, thus exhibiting the glorious OER activity and long-term stability in alkaline solutions. As a result, the optimal NCF@CoNiO2-7 electrocatalyst requires an overpotential of 518 mV for OER at the current density of 100 mA cm−2, which is obvious lower than that of RuO2 (633 mV) and CoNiO2/C-7 as a contrast sample (569 mV), respectively. This work opens up a new path for structural control of 1D bimetallic oxides to improve OER activity and stability.

N-doped one-dimensional carbon framework embedded with CoSe2 nanoparticles as superior electrode for advanced sodium ion storage

Cobalt selenide (CoSe2) is acknowledged as a negative electrode material for sodium-ion batteries (SIBs) due to its high theoretical capacity. However, the significant volume change and inadequate electrochemical performance during charge and discharge processes have limited its practical use in batteries. In this investigation, a straightforward and practical electrospinning method combined with selenization reaction was utilized to fabricate CoSe2 nanoparticles enclosed in nitrogen-doped carbon nanofibers with a three-dimensional self-supporting network structure (CoSe2/N-PCNFs).The CoSe2/N-PCNFs electrode has self-supporting and high conductivity properties, as an anode material for sodium-ion batteries, the discharge capacity of the composite material can reach 450.1 mAh/g after 100 cycles at a current density of 0.2 A/g, and can still maintain a large discharge capacity of 396.9 mAh/g after 500 cycles at a high current density of 1 A/g. The outstanding electrochemical performance is mainly attributed to the superior specific surface area, controllable porous structure, and high pore volume of CoSe2/N-PCNFs Experimental and density functional theory calculations both indicate that the heterojunction interface between CoSe2 and nitrogen-doped carbon can not only promote the adsorption of Na+, but also facilitate electron transfer to significantly improve the rate capability of the material.

Encapsulation hierarchical bimetallic oxide with flexible electrospinning carbon nanofibers for efficient capacitive deionization

Water scarcity, an intensifying issue, has spurred extensive research into the development of sophisticated freestanding pseudocapacitive electrode materials. Characterized by their precise morphology, intricate mechanics, and superior desalination capabilities, these materials are revolutionizing water treatment technologies. However, their broad adoption is hampered by complex fabrication processes and the necessity for various unique components. Herein, the paper introduces a streamlined method combining electrospinning and carbonization to produce a freestanding nitrogen-doped carbon nanofiber encapsulating manganese cobalt oxide (MCO) nanoparticles for desalination purposes. The approach significantly enhances interfacial interactions, mitigates volume shifts during sodium ion adsorption and desorption, and strengthens interfacial stability. Benefiting from its structural and compositional merits, the optimal MCO-1.0 electrode showcases exceptional electrochemical attributes. It achieves an impressive desalination efficiency (34.68 mg g−1), swift capacitive deionization rate (0.58 mg g−1 min−1), and superior cyclic durability. The study enhances our understanding of freestanding carbon fibers encapsulated with metal oxide nanoparticles, a key step toward developing robust electrodes for industrial applications.

Synergistic effect of pore generation and nitrogen doping on the enhanced CO2 capture and selectivity of carbon nanofibers

The porosity and heteroatom doping of carbon materials are crucial for their adsorption capacity and selectivity toward CO2. Herein, nitrogen-doped microporous carbon nanofibers (CNFs) were prepared by carbonizing electrospun polyacrylonitrile (PAN) nanofibers, using nitrogen-rich polyvinylpyrrolidone (PVP) as porogen and nitrogen source simultaneously. The synergistic effect of pore generation and nitrogen doping improved the porosity and preserved a substantial nitrogen content in the CNFs. Compared to the nitrogen-free polyethylene glycol (PEG) porogen, the incorporation of PVP can facilitate nitrogen doping during the carbonization process. With an increasing amount of PVP addition, the specific surface area of the CNFs significantly expanded to 410 m2/g, maintaining a high nitrogen content of 10.32 wt%. The porosity and nitrogen functionalities (Pyridinic N and pyrrolic N) collaborated synergistically in determining CO2 adsorption capacity, with elevated nitrogen content resulted in improved selectivity. The CNFs exhibited remarkable IAST CO2/N2 (10:90) selectivity of 38 and cycling stability, demonstrating their potential for long-term practical applications. This work provides unique inspiration for the design of porous nanofibers with exceptional CO2 adsorption capacity and selectivity.

Ni nanoparticles embedded in multi-channel carbon nanofibers: Self-supporting electrodes for bifunctional catalysis of hydrogen and oxygen evolution reactions

Nitrogen-doped carbon nanofibers with multi-channels loaded with nanoscale nickel particles (Ni-MNCNF) were achieved by the combination of coaxial electrospinning and pyrolysis. Which was used as a self-supporting electrode for electrochemical hydrogen and oxygen evolution reactions. The multi-channels of the fiber facilitated the fast mass transfer as well as endowed it with more exposed active sites. In addition, nanoscale Ni crystals were dispersed evenly on the fiber walls due to the confinement effect of carbon materials. Furthermore, carbon nanofibers provided an excellent conductive network, which expedited the charge transfer rate and further enhanced catalytic activity. At a current density of 10 mA cm−2, the overpotentials for the hydrogen evolution reaction (HER) were only 65 mV and 203 mV in alkaline and acidic electrolytes, respectively, and the overpotential for the oxygen evolution reaction (OER) was 193 mV in an alkaline electrolyte, promoting its potential industrial applications and reducing the negative impact on the environment. This research presented a strategy for designing self-supporting transition metal-based catalysts with superior activity.

Synergistic Engineering of CoO/MnO Heterostructures Integrated with Nitrogen-Doped Carbon Nanofibers for Lithium-Ion Batteries.

The integration of heterostructures within electrode materials is pivotal for enhancing electron and Li-ion diffusion kinetics. In this study, we synthesized CoO/MnO heterostructures to enhance the electrochemical performance of MnO using a straightforward electrostatic spinning technique followed by a meticulously controlled carbonization process, which results in embedding heterostructured CoO/MnO nanoparticles within porous nitrogen-doped carbon nanofibers (CoO/MnO/NC). As confirmed by density functional theory calculations and experimental results, CoO/MnO heterostructures play a significant role in promoting Li+ ion and charge transfer, improving electronic conductivity, and reducing the adsorption energy. The accelerated electron and Li-ion diffusion kinetics, coupled with the porous nitrogen-doped carbon nanofiber structure, contribute to the exceptional electrochemical performance of the CoO/MnO/NC electrode. Specifically, the as-prepared CoO/MnO/NC exhibits a high reversible specific capacity of 936 mA h g-1 at 0.1 A g-1 after 200 cycles and an excellent high-rate capacity of 560 mA h g-1 at 5 A g-1, positioning it as a competitive anode material for lithium-ion batteries. This study underscores the critical role of electronic and Li-ion regulation facilitated by heterostructures, offering a promising pathway for designing transition metal oxide-based anode materials with high performances for lithium-ion batteries.

Work-function-prompted interfacial charge kinetics in hierarchical heterojunction flexible electrode for efficient capacitive deionization

The growing challenge of water scarcity has spurred extensive research into the development of advanced freestanding pseudocapacitive electrode materials. These electrodes, characterized by their controlled morphology, mechanical complexity, and enhanced desalination capabilities, are advancing water treatment technologies. Additionally, electrodes with interfacially influenced heterostructures demonstrate substantial potential to enhance electrochemical kinetics. However, their widespread adoption is hindered by intricate synthesis procedures and the necessity for multiple discrete components. Herein, the report introduces a cohesive approach that utilizes electrospinning and carbonization to create a freestanding, hierarchically porous nitrogen-doped carbon nanofiber network encapsulating FeNi3 alloy (FeNi3@CNFs) for desalination applications. The method enhances the interfacial effect, mitigates volume changes during sodium ion adsorption and desorption, and improves interfacial stability. By capitalizing on structural and compositional advantages, the novel FeNi3@CNFs electrode delivers outstanding electrochemical properties, including a high desalination capacity (46.47 mg g−1 at 1.2 V), rapid desalination rate (0.77 mg g−1 min−1), and enhanced cyclic durability. Computational analysis via Density Functional Theory shows that the work function prompts a surface charge redistribution at the FeNi3@CNFs heterojunction, optimizing the surface electronic structure and reducing the energy barrier for adsorption. The modification significantly boosts the diffusion kinetics of sodium adsorption. The study delineates a comprehensive methodology for fabricating high-performance heterostructured electrode materials that are effective for capacitive deionization.

Accelerating lithium-sulfur battery reaction kinetics and inducing 3D deposition of Li2S using interactions between Fe3Se4 and lithium polysulfides

Although lithium-sulfur batteries (LSBs) exhibit high theoretical energy density, their practical application is hindered by poor conductivity of the sulfur cathode, the shuttle effect, and the irreversible deposition of Li2S. To address these issues, a novel composite, using electrospinning technology, consisting of Fe3Se4 and porous nitrogen-doped carbon nanofibers was designed for the interlayer of LSBs. The porous carbon nanofiber structure facilitates the transport of ions and electrons, while the Fe3Se4 material adsorbs lithium polysulfides (LiPSs) and accelerates its catalytic conversion process. Furthermore, the Fe3Se4 material interacts with soluble LiPSs to generate a new polysulfide intermediate, LixFeSy complex, which changes the electrochemical reaction pathway and facilitates the three-dimensional deposition of Li2S, enhancing the reversibility of LSBs. The designed LSB demonstrates a high specific capacity of 1529.6 mA h g−1 in the first cycle at 0.2 C. The rate performance is also excellent, maintaining an ultra-high specific capacity of 779.7 mA h g−1 at a high rate of 8 C. This investigation explores the mechanism of the interaction between the interlayer and LiPSs, and provides a new strategy to regulate the reaction kinetics and Li2S deposition in LSBs.

Dendritic boron and nitrogen doped high-entropy alloy porous carbon fibers for high-efficiency hydrogen evolution reaction

Among various electrocatalysts, high-entropy alloys (HEAs) have gained significant attention for their unique properties and excellent catalytic activity in the hydrogen evolution reaction (HER). However, the precise synthesis of HEA catalysts in small sizes remains challenging, which limits further improvement in their catalytic performance. In this study, boron- and nitrogen-doped HEA porous carbon nanofibers (HE-BN/PCNF) with an in situ-grown dendritic structure were successfully prepared, inspired by the germination and growth of tree branches. Furthermore, the dendritic fibers constrained the growth of HEA particles, leading to the synthesis of quantum dot-sized (1.67nm) HEA particles, which also provide a pathway for designing HEA quantum dots in the future. This work provides design ideas and guiding suggestions for the preparation of borated HEA fibers with different elemental combinations and for the application of dendritic nanofibers in various fields.

Spinning of Carbon Nanofiber/Ni–Cu–S Composite Nanofibers for Supercapacitor Negative Electrodes

The preparation of composite carbon nanomaterials is one of the methods for improving the electrochemical performance of carbon-based electrode materials for supercapacitors. However, traditional preparation methods are complicated and time-consuming, and the binder also leads to an increase in impedance and a decrease in specific capacitance. Therefore, in this work, we reduced Ni-Cu nanoparticles on the surface of nitrogen-doped carbon nanofibers (CNFs) by employing an electrostatic spinning method combined with pre-oxidation and annealing treatments. At the same time, Ni-Cu nanoparticles were vulcanized to Ni–Cu–S nanoparticles without destroying the structure of the CNFs. The area-specific capacitance of the CNFs/Ni–Cu–S–300 electrode reaches 1208 mF cm−2 at a current density of 1 mA cm−2, and the electrode has a good cycling stability with a capacitance retention rate of 76.5% after 5000 cycles. As a self-supporting electrode, this electrode can avoid the problem of the poor adhesion of electrode materials and the low utilization of active materials due to the inactivity of the binder and conductive agent in conventional collector electrodes, so it has excellent potential for application.

Flexible and crosslinking electrospun porous carbon nanofiber membranes as freestanding binder-free anodes for lithium-ion batteries

Electrospinning carbon nanofibers with one-dimensional nanostructures have enormous potential for electronic applications owing to their flexibility, electrical conductivity, high surface area and attractive structure. In this paper, porous nitrogen-doped carbon nanofiber membranes with chemical crosslinking structure (PNCNMs-CC) were prepared for lithium-ion batteries anodes by crosslinking treatment and carbonization process using polyimide as precursor, melamine as nitrogen source and ethyl orthosilicate as pore-forming agent. The heightened nitrogen content synergizes with the augmented specific surface area, engendering a striking electrochemical enhancement. Rich pore structure provides more active sites. When utilized as a binder-free, current collector-free anode, PNCNMs-CC shows an excellent rate performance and long cycle stability. The first discharge specific capacity of PNCNMs-CC delivered 710 mAh g−1 at 50 mA g−1. After 1000 cycles at a high current density of 1 A g−1, PNCNMs-CC shows 88 % capacity retention, demonstrating a promising candidate as the flexible anodes for high-performance energy storage devices.

Nitrogen-doped carbon nanofiber loaded MOF-derived NiCo bimetallic nanoparticles accelerate the redox transformation of polysulfide for lithium- sulfur batteries

In the electrochemical study of lithium-sulfur (Li-S) batteries, the slow kinetics of the sulfur reduction reaction (SRR) leading to severe shuttle effect of polysulfides remains a major challenge. Catalysts with bimetallic nanoparticles have higher adsorption affinity for lithium polysulfides and hold great potential in improving reaction kinetics. In this study, a nitrogen-doped carbon nanofiber carrier was prepared using high-voltage electrospinning technology, and through in-situ growth and high-temperature pyrolysis process, the carrier material was uniformly loaded with active sites of NiCo bimetallic nanoparticles derived from Metal-organic framework (MOF), aiming to improve the kinetics of sulfur oxidation and reduction and reduce the severe shuttle effect of soluble polysulfides. At the same time, polymethyl methacrylate was added to adjust the pore structure of the carbon nanofibers to form an ideal independent sulfur cathode porous conductive carbon network for rapid ion transport to prevent Li2S deposition and alleviate the volume change during lithiation/delithiation process. Experimental results show that the synergistic catalytic effect of bimetallic nanoparticles can not only rapidly anchor lithium polysulfides throughout the entire reaction process of Li-S batteries, but also reduce the resistance during the reaction process, accelerating the conversion of lithium polysulfides to Li2S deposition. It demonstrates outstanding electrochemical performance, with a first-cycle discharge specific capacity as high as 1431.7 mAh g−1 at a 0.2 C rate, and a Coulombic efficiency of 96%. After 500 cycles, its capacity still maintains at 628.5 mAh g−1, with a decay rate of only 0.11% per cycle. This study provides a feasible insight into the synergistic catalysis of MOF-derived metal nanoparticles, which has important guiding significance and potential impact on the catalysis of Li-S batteries by bimetallic nanoparticles with an independent sulfur cathode structure, and is expected to accelerate the industrialization process of Li-S batteries.

Unveiling the Synergy of Architecture and Anion Vacancy on Bi2Te3-x@NPCNFs for Fast and Stable Potassium Ion Storage.

Large volume strain and slow kinetics are the main obstacles to the application of high-specific-capacity alloy-type metal tellurides in potassium-ion storage systems. Herein, Bi2Te3-x nanocrystals with abundant Te-vacancies embedded in nitrogen-doped porous carbon nanofibers (Bi2Te3-x@NPCNFs) are proposed to address these challenges. In particular, a hierarchical porous fiber structure can be achieved by the polyvinylpyrrolidone-etching method and is conducive to increasing the Te-vacancy concentration. The unique porous structure together with defect engineering modulates the potassium storage mechanism of Bi2Te3, suppresses structural distortion, and accelerates K+ diffusion capacity. The meticulously designed Bi2Te3-x@NPCNFs electrode exhibits ultrastable cycling stability (over 3500 stable cycles at 1.0 A g-1 with a capacity degradation of only 0.01% per cycle) and outstanding rate capability (109.5 mAh g-1 at 2.0 A g-1). Furthermore, the systematic ex situ characterization confirms that the Bi2Te3-x@NPCNFs electrode undergoes an "intercalation-conversion-step alloying" mechanism for potassium storage. Kinetic analysis and density functional theory calculations reveal the excellent pseudocapacitive performance, attractive K+ adsorption, and fast K+ diffusion ability of the Bi2Te3-x@NPCNFs electrode, which is essential for fast potassium-ion storage. Impressively, the assembled Bi2Te3-x@NPCNFs//activated-carbon potassium-ion hybrid capacitors achieve considerable energy/power density (energy density up to 112 Wh kg-1 at a power density of 1000 W kg-1) and excellent cycling stability (1600 cycles at 10.0 A g-1), indicating their potential practical applications.

Synthesis of 3D CC/NCNF/NiFe LDH composites as highly active oxygen evolution reaction electrocatalysts

Nitrogen doped carbon nanofibers (NCNFs), which are grown on carbon cloth (CC) and loaded with NiFe layered double hydroxide (LDH) nanosheets, are synthesized by chemical vapor deposition, ammonia annealing and electrodeposition. The obtained three dimensional CC/NCNF/NiFe LDH composites demonstrate an overpotential of 220 mV at current density of 10 mA cm−2 and a small Tafel slope of 30 mV dec−1 for oxygen evolution reaction (OER), both of which are superior to those of the state-of-the-art iridium oxide catalysts. The excellent OER performances of the CC/NCNF/NiFe LDH composites may be attributed to collective contributions of large surface areas of CNFs, nitrogen doping and synergy between NCNFs and NiFe LDHs.