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Nickel cobalt phosphide/carbon nanofibers (NiCoP/C) with an average diameter of approximate 200 nm are prepared by electrospinning combined with calcinations. Carbon nanofibers with an average pore size of 10.77 nm as conductive skeletons support the dispersed NiCoP nanoparticles with the size ranging from 20 to 80 nm, providing abundant reactive sites and facilitating the electrochemical reactions. The specific capacitance of NiCoP/C reaches 478 F g−1 at 2 A g−1 in a 3 M KOH electrolyte, showing superior electrochemical properties compared to its counterparts. After 5000 charge/discharge cycles at 10 A g−1, 99.99 % of initial specific capacitance is retained. In addition, an asymmetric supercapacitor assembled using NiCoP/C as positive electrode and activated carbon as negative electrode exhibits an energy density of 16.72 Wh kg−1 at a high-power density of 7250 W kg−1. Furthermore, the capacitance loss of the supercapacitor is only 0.04 % after 5000 cycles at 10 A g−1, which is mainly attributed to the enhanced stability of NiCoP nanoparticles owing to the assistance of carbon nanofibers as the skeleton. The synergistic effects of NiCoP nanoparticles and carbon nanofibers result in the boosted electrochemical performances. This study demonstrates the potential application of carbon nanofibers as conductive skeletons for nanostructured electrodes. • NiCoP/C nanofibers were prepared by electrospinning without the emission of PH 3. • Carbon nanofibers acted as skeletons and conductive channels for NiCoP. • Assembled NiCoP/C//AC supercapacitor achieved 16.72 Wh kg−1 at 7250 W kg−1. [ABSTRACT FROM AUTHOR]

Using renewable biomass precursors to develop high-performance carbon electrodes is a promising approach for the advancement of supercapacitors. This work proposes a feasible strategy to prepare self-supporting flexible porous carbon nanofibers by electrospinning and carbonizing the mixture of cuttlefish ink, polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA). The impacts of cuttlefish ink precursor on the structure, elemental composition, and capacitance properties of carbon nanofibers have been studied. Herein, the unique structural advantage of cuttlefish ink can significantly optimize the porous structure of carbon nanofibers. Due to the hierarchical porous structure, large specific surface area, hollow channels and high nitrogen content, the carbon nanofibers offer a high specific capacitance of 364.8 F g−1 at 0.5 A g−1 current density, alongside desirable rate performance and cycle life. Furthermore, the carbon nanofiber electrode performs good mechanical flexibility. The flexible solid-state supercapacitor based on this electrode exhibits 14.1 Wh kg−1 energy density at 0.4 kW kg−1 power density, and 97.8% capacitance retention after 5000 cycles. The favorable capacitive properties make this carbon nanofiber material a potential candidate for supercapacitor electrodes. [Display omitted] • Electrospun porous carbon nanofibers (CPP–CNF) were prepared from cuttlefish ink. • CPP-CNF features hierarchical pores and hollow channels. • CPP-CNF is mechanically flexible with superior capacitive performance. • The flexible supercapacitor achieves high energy density and cycling stability. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Hierarchically porous nitrogen-doped carbon (P–N–C) nanofibers are prepared. • Comprising VN nanodots and densified entangled N-doped CNTs (N-CNTs). • VN nanodots act as chemisorption sites for efficient anchoring of lithium polysulfide. • N-CNTs increase the overall conductivity of the nanostructure framework. • Li–S cell with P–N–C@VN/N-CNT NF-coated separator exhibits stable performance. [ABSTRACT FROM AUTHOR]

Designing cathode and anode materials that can accommodate capacity and rate performance is a significant challenge in developing lithium-ion capacitors (LICs). Herein, we synthesize a unique N/S dual-doped hierarchical porous carbon (NSC) under the effect of pore distribution modification and heteroatom doping. The nanosheet shape and pore distribution of NSC are highly adjustable, while it demonstrates a reversible capacity that is tens of times more than that of unaltered pristine active carbon. Meanwhile, the prepared glycerol-engineered polyacrylonitrile nanofiber (GPN) form a fast conducting network in the presence of glycerol and carbon nanotubes (CNTs) and exhibit a 300% higher capacity compared to pure polyacrylonitrile nanofibers at 5 A g−1. On this premise, the constructed highly stable LIC (NSC//GPN x @CNTs) can achieve an energy density of 131.48 Wh kg−1 and have an excellent capacity retention rate (93.5%) over 10,000 cycles at a high current density (5 A g−1). This work may lead to new avenues for the preparation of heteroatom-doped porous carbon and redefine the electrode matching of highly stable LICs. [Display omitted] • Highly tunable pore distribution and nanosheet shape of porous carbon. • The cathode nanofibers exhibit high electrical conductivity. • The LIC achieves high energy density and high power density simultaneously. [ABSTRACT FROM AUTHOR]

Electrospinning technology has been extensively used to prepare electrodes for vanadium redox flow batteries (VRFBs). Nevertheless, electrospinning carbon nanofibers (ECNFs) electrodes suffer from low porosity and poor permeability, hence significantly hindering mass transport. To solve this critical issue, a new approach to prepare porous channel electrodes with large porosity based on electrospinning technology is proposed. The electrode is fabricated by electrospinning of polyacrylonitrile and poly (methyl methacrylate) (PMMA) solutions. PMMA not only acts as a sacrificial phase to form a porous channel structure inside the fibers, but also interconnects the fibers, which significantly increases the inter-fiber pore space and enhances the mass transfer performance. Electrochemical characterizations indicate that the electrodes have a remarkably elevated electrochemical specific surface area and outstanding electrochemical performance. Owing to the well-designed large-porosity porous channel structure of the electrode, the energy efficiency of the VRFB equipped with this electrode is 74.45% at 300 mA cm−2 and 81.03% at 200 mA cm−2, and the battery can be continuously charged and discharged for more than 1200 cycles, which demonstrates a long-term cycling stability of the electrode. All of these indicate that this efficient and durable method for propagating electrode has broad application prospects. [Display omitted] • Prepared an electrode with porous channel structure. • The electrodes exhibit enlarged pores while retaining large specific surface areas. • The design greatly improves activity of electrodes. • The prepared electrodes enable a significant enhancement in the battery performance. [ABSTRACT FROM AUTHOR]

Carbon nanofibers (CNFs) have been playing an essential role in addressing the challenges of the flexibility in energy storage devices. However, the unsatisfactory electrochemical performance and poor electrical conductivity are often caused by insufficient physical contact points of CNFs. The design and implementation of unique electrodes are expected to overcome these issues. Here, the N-doped hierarchical porous carbon nanofibers (NCNFs) hollow framework derived from metal-organic frameworks (MOFs) is fabricated, which is decorated with high conductive reduced graphene oxide rGO and single-crystal ZnO nanorod for engineering the binder-free flexible electrodes NCNF@rGO-x@ZnO. The obtained NCNF@rGO-7@ZnO electrode exhibits the desired specific capacitance of 473 F g-1. An assembled hybrid supercapacitor exhibits the high energy density of 35.16 Wh kg-1 at the power density of 747.2 W kg-1, and superior cycling life. Given these advantages, the NCNF@rGO-7@ZnO is selected as the electrode in a flexible and foldable supercapacitor. There is exceptional flexibility and no visible capacitance loss when the supercapacitor bending at different angles. Furthermore, a timer is successfully driven by two supercapacitor devices connected in series. Hence, a flexible binder-free electrode with excellent electrochemical performance can be obtained by engineering the structure into a hollow interconnected architecture and the rational design of materials. [Display omitted] • The design and structural engineering of unique binder-free electrodes are proposed. • The supercapacitor exhibits considerable flexibility and long cycling stability. • The remarkable performance is related to the rational structure design. • A typical ASC device shows the potential practical application. [ABSTRACT FROM AUTHOR]

As the precursor of MXenes (2D transition metal carbides, carbon nitrides and nitrides), MAX phase materials have attracted ever-increasing attention in electrochemical applications. In this work, we have successfully hybridized a MAX phase, Ti 2 SnC, with various ratios of carbon nanofibers (CNFs) via electrospinning. The results show that the Ti 2 SnC/CNFs compounds possess a stable lithium ion storage ability as an anode material, reaching a stable specific capacity of up to 367.5 mAh·g−1 after 500 charge/discharge cycles at the current density of 1.0 A g−1, which are drastically better than some other MAX phase materials such as Ti 3 SiC 2 and Nb 2 SnC. This strategy provides a new pathway for the improvement of the electrochemical stability of MAX phase, which has a wide application prospect. • Ti 2 SnC/CNFs was successfully prepared by an electrospinning method. • CNFs retard the volume expansion of Ti 2 SnC during the charge/discharge process. • Ti 2 SnC/CNFs performed stable lithium ion capacitance (367.5 mAh·g−1 at 1.0 A g−1). [ABSTRACT FROM AUTHOR]

Flexible electrochemical energy storage devices play a vital role in the subject of flexible wearable digital equipment. The key is to devise electrodes with wonderful flexibility, high capacity, and preeminent cycle stability. Therefore, we use tetraethyl orthosilicate as the coupling agent to develop Sb 2 Se 3 /Sb uniformly embedded in carbon nanofibers by electrospinning. Silicon oxide act as a form-stabilizing enhancer, the Sb 2 Se 3 /Sb/C nanofibers membrane exhibits superior mechanical flexibility and splendid electrochemical potassium storage performance. In specific, as the free-standing electrode, Sb 2 Se 3 /Sb/C nanofibers membrane can achieve a high reversible discharge capacity of 372 mAh g−1 at 0.05 A g−1 and 228 mAh g−1 at 1 A g−1 and deliver capacity retention of about 100% at 0.1 A g−1 after 300 cycles. All of these phenomena make it hopeful for the application in flexible potassium-ion batteries. [Display omitted] • Flexible and foldable Sb 2 Se 3 /Sb/C nanofibers membrane was prepared. • Ethyl orthosilicate improved the flexibility of the nanofibers membrane. • Free-standing Sb 2 Se 3 /Sb/C nanofibers membrane showed excellent performance. [ABSTRACT FROM AUTHOR]

Sluggish extracellular electron transfer (EET) at the anode interface is the major obstacle to achieving satisfactory power density in microbial fuel cells (MFCs). To boost the EET efficiency, herein the anode electrocatalysts, nitrogen-doped carbon nanofibers anchoring Fe nanoparticles (Fe/N-x@CNFs, x = 0.5, 1, 3, 5), are rationally designed via electrospinning and calcination process. The morphology and structure characterization indicates that the Fe/N-3@CNFs electrocatalyst presents a porous structure with uniformly distributed Fe nanoparticles on the carbon matrix, which offer a large-accessible surface area for electroactive bacteria habitation along with facilitated EET efficiency. Electrochemical measurements demonstrate that the as-fabricated Fe/N-3@CNFs exhibit excellent electrocatalytic activity for the charge transfer on the anode, endowing the cell with a maximum power density of 1873.8 mW m−2, which is 1.8 and 3.6 times higher than that of Fe@CNFs (1039.2 mW m−2) and carbon cloth (519.8 mW m−2). The outstanding performance of Fe/N-3@CNFs can be attributed to the increased electronic conductivity of carbon matrix with melamine additives, the enriched electroactive bacteria as demonstrated by high-throughput sequencing, and the released positively charged iron mediators to promote EET efficiency. This investigation introduces an effective method of constructing high-efficient anode electrocatalysts for enhancing the output MFCs performance. [Display omitted] • The Fe/N-3@CNFs anode electrocatalysts are fabricated via electrospinning. • The Fe/N-3@CNFs have excellent biocompatibility. • The bacterial loading content and interfacial charge transfer are improved. • The output power is 3.6 folds higher compared to pristine carbon cloth. • The digital watch and LED light can be lightened. [ABSTRACT FROM AUTHOR]

An efficient, robust and low-cost bifunctional electrocatalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is essential to high-performance zinc-air batteries (ZABs). Metal-nitrogen-carbon (M-N-C) systems have attracted considerable attention recently. Herein, a novel Co-N x -enriched electrospun porous carbon nanofibrous bifunctional electrocatalyst (Co-N x /EPCF) is prepared by electrospinning with cobalt nitrate and SiO 2 , followed by carbonization and acid etching. The catalyst displays an outstanding electrocatalytic activity of reversible oxygen overpotential (ΔE = E j = 10 - E 1/2 = 0.87 V), as well as a high stability. The first-principal calculation reveals that the Co–N–C structure has better ORR paths than that of Co cluster. Furthermore, based on the electrocatalyst, the assembled flexible ZABs possess a power density of 81 mW cm−2, a capacity of 807 mAh g zn −1, and 111 stability cycles. The study provides a novel strategy to prepare high-performance bifunctional catalysts for wearable power sources. [Display omitted] • Electrospun porous carbon nanofibers are prepared by hard template method. • Co-N x -enriched catalyst drives energy-efficient ORR/OER kinetics with ΔE = 0.87 V. • Flexible ZABs achieve a power density of 81 mW cm−2 and a cycle time of 37 h. [ABSTRACT FROM AUTHOR]

Developing high-capacity anode materials based on metal sulfides is of great importance for building advanced lithium-ion batteries (LIBs). Herein, we demonstrate rational encapsulation of cobalt sulfide (CoS x) nanoparticles into multichannel carbon nanofibers (CoS x /MCF) with substantially improved Li+ reactivity and durability. The unique multichannel and conductive carbon scaffold not only affords boosted electron/Li + transportation pathways for fast redox reaction with CoS x , but also stabilizes the electrode structure by buffering the volume change of CoS x. Impressively, the CoS x /MCF composite could serve as flexible anodes to deliver a high reversible capacity of 737 mAh g−1 at 0.2 A g−1 after 100 cycles, superior rate capacity of 374 mAh g−1 at 5 A g−1, and excellent operating stability over 1000 cycles. Practical feasibility is also demonstrated by a full cell based on the high-capacity CoS x /MCF anode and Li[Ni 0.8 Co 0.1 Mn 0.1 ]O 2 cathode. The present study may provide insights for the facile synthesis of advanced anode materials for high-performance LIBs. [Display omitted] • Multichannel carbon nanofibers are developed to encapsulate ultrafine CoS x. • Axial nanochannels buffer volume change of CoS x and boost the reaction kinetics. • Freestanding CoS x /MCF electrode shows superior performance of lithium storage. [ABSTRACT FROM AUTHOR]