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[Display omitted] Recently, microwave absorption (MA) materials have attracted intensive research attention for their ability to counteract the effects of ever-growing electromagnetic pollution. However, conventional microwave absorbers suffer from complex fabrication processes, poor stability and different optimal thicknesses for minimum reflection loss (RL min) and widest effective absorption bandwidth (EAB). To address these issues, we have used electrospinning followed by high-temperature annealing in argon to develop a flexible microwave absorber with strong wideband absorption. The MA properties of the carbon nanofibers (CNFs) can be tuned by adjusting annealing temperature, and are dependent on the composition and microstructure of the CNFs. The absorber membrane obtained at 800 °C consists of Fe 0.64 Ni 0.36 @graphite core–shell nanoparticles (NPs) embedded in CNFs, formed via a corrosion-like transformation from NiFe 2 O 4 to Fe 0.64 Ni 0.36 followed by surface graphitization. This nanostructure greatly enhances magnetic-dielectric synergistic loss to achieve superior MA properties, with an RL min of −57.7 dB and an EAB of 6.48 GHz (11.20–17.68 GHz) both acquired at a thickness of 2.1 mm. This work provides useful insights into structure–property relationship of the CNFs, sheds light on the formation mechanism of Fe 0.64 Ni 0.36 @graphite NPs, and offers a simple synthesis route to fabricate light-weight and flexible microwave absorbers. [ABSTRACT FROM AUTHOR]

Carbon nanofiber (CNF) films or mats have great conductivity and thermal stability and are widely used in different technological processes. Among all the fabrication methods, electrospinning is a simple yet effective technique for preparing CNF mats, but the electrospun CNF mats are often brittle. Here, we report a feasible protocol by which to control the alignment of carbon black nanoparticles (CB NPs) within CNF to enhance the flexibility. The CB NPs (~45 nm) are treated with non-ionic surfactant Triton-X 100 (TX) prior to being blended with a solution containing poly(vinyl butyral) and polyacrylonitrile, followed by electrospinning and then carbonization. The optimized CB-TX@CNF mat has a boosted elongation from 2.25% of pure CNF to 2.49%. On the contrary, the untreated CB loaded in CNF displayed a lower elongation of 1.85% because of the aggregated CB spots created weak joints. The controlled and uniform dispersion of CB NPs helped to scatter the applied bending force in the softness test. This feasible protocol paves the way for using these facile surface-treated CB NPs as a commercial reinforcement for producing flexible CNF films. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rh nanoparticles anchored on Co/ N -doped carbon nanofibers are prepared via an electrospinning-pyrolysis-reduction method. • The nanofibrous hybrid catalyst shows rich exposed active sites and excellent electrical conductivity. • The nanofibrous hybrid catalyst presents high HER activities in both alkaline and acidic media. • The nanofibrous hybrid catalyst presents an excellent long-term stability towards HER. Constructing high-activity electrocatalysts towards hydrogen evolution reaction (HER) is an essential way to achieve efficient, green and sustainable energy from water electrolysis. In this work, rhodium (Rh) nanoparticles anchored on cobalt (Co)/nitrogen (N)-doped carbon nanofibers (NCNFs) catalyst is prepared by the electrospinning-pyrolysis-reduction method. The synergy effect between Co-NCNFs and Rh nanoparticles contributes to the superior HER activity and favorable durability. The optimized 0.15Co-NCNFs-5Rh sample exhibits ultralow overpotentials of 13 and 18 mV to reach 10 mA cm−2 in an alkaline and acidic electrolyte, surpassing many Rh-based or Co-based electrocatalysts reported in the literature. Additionally, the Co-NCNFs-Rh sample shows a better HER activity than benchmark Pt/C catalyst in an alkaline medium at all current densities and in an acidic condition at higher current densities, offering its promising practical applications. Thus, this work provides an efficient methodology to construct high-performance HER electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrochemical nitrate (NO 3 −) reduction is a promising approach to relieve nitrate pollution and produce value-added ammonia (NH 3), but efficient and durable catalysts are required due to the large bond dissociation energy of nitrate and low selectivity. Herein, we propose chromium carbide (Cr 3 C 2) nanoparticles loaded carbon nanofibers (Cr 3 C 2 @CNFs) as electrocatalysts to convert nitrate to ammonia. In phosphate buffer saline containing 0.1 mol L−1 NaNO 3 , such catalyst achieves a large NH 3 yield of 25.64 mg h−1 mg−1 cat. and a high faradaic efficiency of 90.08% at −1.1 V vs the reversible hydrogen electrode, which also shows excellent electrochemical durability and structural stability. Theoretical calculations reveal the adsorption energy for nitrate at Cr 3 C 2 surfaces reaches −1.92 eV and the potential determining step (*NO→*N) for Cr 3 C 2 hits a low energy increase of 0.38 eV. [ABSTRACT FROM AUTHOR]

Exploring anode materials with an excellent electrochemical performance is of great significance for supercapacitor applications. In this work, a N-doped-carbon-nanofiber (NCNF)-supported Fe3C/Fe2O3 nanoparticle (NCFCO) composite was synthesized via the facile carbonizing and subsequent annealing of electrospinning nanofibers containing an Fe source. In the hybrid structure, the porous carbon nanofibers used as a substrate could provide fast electron and ion transport for the Faradic reactions of Fe3C/Fe2O3 during charge–discharge cycling. The as-obtained NCFCO yields a high specific capacitance of 590.1 F g−1 at 2 A g−1, superior to that of NCNF-supported Fe3C nanoparticles (NCFC, 261.7 F g−1), and NCNFs/Fe2O3 (NCFO, 398.3 F g−1). The asymmetric supercapacitor, which was assembled using the NCFCO anode and activated carbon cathode, delivered a large energy density of 14.2 Wh kg−1 at 800 W kg−1. Additionally, it demonstrated an impressive capacitance retention of 96.7%, even after 10,000 cycles. The superior electrochemical performance can be ascribed to the synergistic contributions of NCNF and Fe3C/Fe2O3. [ABSTRACT FROM AUTHOR]

Molybdenum carbide co-catalyst and carbon nanofiber matrix are suggested to improve the nickel activity toward methanol electrooxidation process. The proposed electrocatalyst has been synthesized by calcination electrospun nanofiber mats composed of molybdenum chloride, nickel acetate, and poly (vinyl alcohol) under vacuum at elevated temperatures. The fabricated catalyst has been characterized using XRD, SEM, and TEM analysis. The electrochemical measurements demonstrated that the fabricated composite acquired specific activity for methanol electrooxidation when molybdenum content and calcination temperature were tuned. In terms of the current density, the highest performance is attributed to the nanofibers obtained from electrospun solution having 5% molybdenum precursor compared to nickel acetate as a current density of 107 mA/cm2 was generated. The process operating parameters have been optimized and expressed mathematically using the Taguchi robust design method. Experimental design has been employed in investigating the key operating parameters of methanol electrooxidation reaction to obtain the highest oxidation current density peak. The main effective operating parameters of the methanol oxidation reaction are Mo content in the electrocatalyst, methanol concentration, and reaction temperature. Employing Taguchi's robust design helped to capture the optimum conditions yielding the maximum current density. The calculations revealed that the optimum parameters are as follows: Mo content, 5 wt.%; methanol concentration, 2.65 M; and reaction temperature, 50 °C. A mathematical model has been statistically derived to describe the experimental data adequately with an R2 value of 0. 979. The optimization process indicated that the maximum current density can be identified statistically at 5% Mo, 2.0 M methanol concentration, and 45 °C operating temperature. [ABSTRACT FROM AUTHOR]

Sol-gel electrospinning process was used to prepare electrospun carbon nanofibers (ECNFs) from polyacrylonitrile and graphite nanoplatelets. The nanofibers of as-electrospun carbon were calcinated in argon from room temperature to 500 °C for 1h. Scanning and transmission electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffractometry (XRD) were used to characterize the synthesized ECNFs. The smooth ECNFs with a diameter of 129 ± 43 nm comprised conical platelets of 30–200 µm length. The plane-layered nanofibers contained crystallites along the long fiber axis and were mainly parallel. [ABSTRACT FROM AUTHOR]

Rational design of hybrid electrocatalysts of nanostructured non-precious metals/metal compound on highly conductive substrates is significant to enhance oxygen reduction activity for clean energy conversion. However, the limited exposure of active sites and sluggish mass transport on electrode trade-off the intrinsic performance of electrocatalyst. Herein, we report a strategic method to fabricate electrocatalyst with well-dispersed iron-based mixed nanoparticles embedding in nitrogen-doped carbon nanofibers (Fe-Fe 3 C/Fe 3 N@NCNFs) and demonstrate desired properties of the material, such as hierarchically porous structure, large specific surface area, and well-dispersion of mixed nanoparticles. The Fe-Fe 3 C/Fe 3 N@NCNFs electrocatalyst also exhibits high-performed activity in oxygen reduction reaction (ORR) with high onset potential of 0.998 V and half wave potential of 0.85 V, as well as high stability and methanol tolerance, which is even superior to benchmark performance of commercial Pt/C. In addition, a zinc-air battery assembled with Fe-Fe 3 C/Fe 3 N@NCNFs as the air cathode shows high open-circuit voltage (1.466 V), high specific capacities (778 mA h g−1 at 5 mA cm−2), excellent reversibility and stability. The remarkable improvement of electrocatalytic performance validates paramount advantages, attributing from the inter-connected conduction network and well-dispersed active sites on carbon nanofiber surface, over mass transfer process and maximizing exposure of catalytic sites [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] The elaborative design and construction of first-rank bifunctional oxygen electrocatalysts featuring low price, high activity and strong stability is critical for the large-scale applications of rechargeable Zn-air batteries. Here, a resultful strategy is proposed for fabricating nitrogen-doped 1D beaded-like structure carbon nanofibers uniformly decorated with nitrogen-doped CuCo 2 O 4 nanoparticles (N-CuCo 2 O 4 @CNFs) toward boosting oxygen evolution reaction/oxygen reduction reaction (OER/ORR) catalysis. Taking advantage of the synergistic effect between interconnected 1D hierarchical porous carbon nanofiber structure and high catalytic activity of N-doped CuCo 2 O 4 nanoparticles derived from bimetallic MOFs, the N-CuCo 2 O 4 @CNFs catalysts possess enhanced reaction kinetics and preferable charge transfer ability. Impressively, the obtained catalysts exhibit prominent electrocatalytic ability and superior stability for OER/ORR, even surpass the commercial RuO 2 and Pt/C. More significantly, the Zn-air batteries employing the N-CuCo 2 O 4 @CNFs-800 as cathode display a higher power density of 175.6 mW cm−2, a lower charge-discharge voltage gap of 0.82 V at 10 mA cm−2, as well as a better cycling stability with respect to those of Pt/C + RuO 2 mixture, demonstrating the great potential of N-CuCo 2 O 4 @CNF as a high-efficiency catalyst for clean energy devices. [ABSTRACT FROM AUTHOR]

Novel composites of graphene-beaded porous carbon nanofibers decorated with TiO2 (G/PCF/TiO2) were synthesized using an electrospinning method and their photocatalytic performance was demonstrated based on the degradation of methylene blue (MB) under visible light irradiation. The enhanced photocatalytic properties of G/PCF/TiO2 can be ascribed to the synergistic effect of graphene-beaded porous carbon nanofibers, which facilitates charge transfer, increases the light absorption in the visible range, as well as favors the adsorption of dye. The present strategy provides an effective strategy for the preparation of carbon-based composite and its application for high-performance photocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Low-loading and ultrasmall Ir nanoparticles on Ni/N-doped carbon nanofibers (NCNFs) are fabricated. • The nanofibrous NCNFs with both Ir and Ni provide rich exposed active sites and excellent electrical conductivity. • The Ni-NCNFs-Ir catalyst exhibits excellent HER activity in both acidic and alkaline media. • The Ni-NCNFs-Ir catalyst also presents a favorable durability during HER process. The construction of highly active and durable electrocatalysts for hydrogen production from water electrolysis in a wide pH range is crucial for the sustainable development of clean energy. In this work, low-loading and ultrasmall Ir nanoparticles decorated on the surface of Ni/nitrogen-doped carbon nanofibers (NCNFs) are rationally constructed through a simple chemical reduction deposition route. Benefiting from the rich electrochemical active sites and excellent electrical conductivity, the obtained Ni-NCNFs-Ir catalyst exhibits superior hydrogen evolution reaction (HER) activities in both acidic and alkaline solutions. Specifically, the optimized 0.1Ni-NCNFs-5Ir catalyst with Ir content of 6.0 wt% exhibits remarkable low overpotentials of 22 and 25 mV at 10 mA cm−2 in 0.5 M H 2 SO 4 and 1 M KOH, respectively, which are better than many other reported Ir- or Ni-based electrocatalysts. In addition, the prepared 0.1Ni-NCNFs-5Ir catalyst shows favorable durability. Our theoretical results reveal that the relevant C- and Ir-sites jointly contribute to the high HER catalytic property of the Ni-NCNFs-Ir system, and two complicated electron transfer processes (Ni → C → N and Ir → C → N) are beneficial to promote the electrocatalytic performance. This work provides a meaningful strategy to develop high-efficiency HER electrocatalysts in a wide pH range. [ABSTRACT FROM AUTHOR]

Electrospinning has been used as a convenient technology to produce high-energy and self-standing anodes for lithium-ion batteries (LIBs) by encapsulating silicon nanoparticles (Si/NPs) into carbon nanofibers (CNF). However, the inhomogeneous distribution of Si/NPs in CNF results in low coulombic efficiency, rapid capacity decay and slow kinetics during cycling process which hinder the practical application of this promising composite anode. In this work, a principle of universal design is applied to the manufacture of Si-CNF composites, in this way, a self-standing electrode with homogeneous distribution of Si/NPs in CNF (Si//PCNF-15) is developed by introducing triblock copolymer Pluronic P123 (polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer) as dispersant and pore directing agent. As anode of LIBs, the Si//PCNF-15 exhibits outstanding electrochemical performance and considerable flexibility due to the homogeneous dispersion of Si nanoparticles and high graphitization of the carbon network. As results, a specific capacity of 1074.8 mAh g−1 at 0.3 A g−1 and a rate capacity of 236.1 mAh g−1 at 10 A g−1 have been delivered when it is explored as a self-standing anode for LIBs. This work provides a universal approach for developing self-standing anodes of composite fibers with nanoparticles dispersed homogeneously in CNF. [Display omitted] • Composite fibers of carbon encapsulated Si nanoparticles are got by electrospinning. • P123 surfactant play dual-role as Si dispersant and pore director of carbon nanofibers. • Even dispersion of Si nanoparticles and formation of mesopores are achieved by P123. • The composite is used as self-standing anode for high-performance lithium-ion battery. [ABSTRACT FROM AUTHOR]

Ruthenium (Ru) is considered as a promising element for constructing alkaline hydrogen evolution (HER) catalysts due to its rapid water dissociation kinetics and low-cost advantages than Pt. Alloying can optimize the electrochemical performance of metals and reduce the usage of the noble metal. Herin, RuCo alloy nanoparticles were grown in-situ on N-doped carbon nanofibers (RuCo/NCNF) by electrospinning and graphitization. Under thermodynamic driving force, the Ru and Co elements formed RuCo alloys. It is worth noting that the Ru not only improved the catalytic performance, but also reduced the nanoparticle size and exposing more active sites. Moreover, N-doped carbon nanofiber was not only used to load RuCo alloy nanoparticle, but also as a good substrate for the HER reaction. Therefore, the RuCo/NCNF had fabulous catalytic activity in alkaline media. Furthermore, the in-situ growth also endowed the RuCo/NCNF with excellent stability, HER performance was not significantly reduced even after 40 h stability test. And when the Ru:Co = 1:8, RuCo/NCNF had the excellent HER catalytic performance. Only 41 mV was required to drive a current density of 10 mA cm−2, with Tafel Slope as low as 64.8 mV dec−1. • RuCo alloy nanocrystals were growing in-situ on N-doped carbon nanofibers. • The strong synergetic behavior between Ru and Co via alloying improved and optimized the electrochemical performance of catalysts. • RuCo alloy nanocrystals anchored on N-doping carbon nanofibers exhibit exceedingly low overpotentials and small Tafel slopes in alkalinemV. • It presents superb conductivity and durable stability with the existence and protection of carbon. [ABSTRACT FROM AUTHOR]

Manufacturing lightweight, ultralow filler loading, broad bandwidth and highly efficient microwave absorbers is still a challenge. Herein, we have synthesized Co nanoparticles decorated N-self-doped carbon nanofibers (Co@NCNFs) composite by electrospinning followed by a two-step heat treatment and investigated its electromagnetic (EM) and microwave absorption performances under different filler contents (from 2.5 to 7.5 wt%) in paraffin wax matrix. It is found that the Co@NCNFs composite has strong ferromagnetism and moderate graphitization degree as well as abundant polar groups and defects, and Co nanoparticles encapsulated by graphitic carbon layers with sizes around 45–115 nm are uniformly dispersed in the NCNFs. With increasing the filler loading, the EM attenuation ability is gradually strengthened while the impedance matching level is just the opposite. The EM absorbing properties of the composites are more superior within 5.0 wt% Co@NCNFs loading owing to the synergy of improved impedance matching and satisfactory EM dissipation ability. Under an ultralow filler loading of 2.5 wt%, the optimal reflection loss (RL) can reach as strong as −49.3 dB at 17.83 GHz with a thin thickness of 1.61 mm and the maximum effective absorption bandwidth (EAB, RL<−10.0 dB) is as wide as 5.44 GHz (12.56–16.99 GHz) at 1.92 mm. When the filler loading is only 5.0 wt%, a minimum RL value of −52.3 dB is achieved at 6.36 GHz with the thickness of 3.03 mm and the maximum EAB is 4.64 GHz (13.36–18.00 GHz) at 1.42 mm. Compared to other Co/C composite absorbers, the as-prepared Co@NCNFs composite with well-designed constitute and structure demonstrates the better comprehensive absorption performance at a much lower filler loading. Therefore, the present Co@NCNFs may be more promising for practical applications as lightweight and high-performance EM wave absorbers especially in the medium and high frequency range. [Display omitted] • 1D Co@NCNFs were fabricated as lightweight and highly efficient microwave absorber. • The microwave absorption performance is more superior within 5 wt% filler loading. • The minimal reflection loss reaches −49.3 dB at ultralow filler content of 2.5 wt%. • A maximum effective absorption bandwidth of 5.44 GHz can be achieved. • Well-designed constitute and structure are responsible for the excellent property. [ABSTRACT FROM AUTHOR]

Silicon-based electrodes hold a great potential application in lithium-ion batteries (LIBs) due to the high-energy-density. However, huge volume expansion and poor electric conductivity hinder the commercial application of silicon-based materials. To alleviate these problems, two different hierarchical core-shell composites, silicon/carbon@porous carbon nanofibers (Si/C@PCNF) and silicon@hollow porous carbon nanofiber (Si@HPCNF) are designed and prepared through coaxial electrospinning. The shell layer prevents silicon contacting with electrolyte directly, and the porous carbon nanofibers shorten Li+ diffusion distance and facilitate ion transport. Compared with Si@HPCNF composites, Si/C@PCNF composites achieve a better electrochemical performance owing to the high surface area (68.05 m2/g) and the fact that silicon nanoparticles are connected to each other by porous carbon in the core. The Si/C@PCNF electrodes deliver a large reversible capacity (842.1 mAh∙g−1 after 500 cycles at 0.5 A∙g−1), a good rate capability (1366.6 mAh∙g−1 at 0.5 A∙g−1) and an excellent cycle stability (420.3 mAh∙g−1 at 2.0 A∙g−1 after 1000 cycles), indicating that it can be served as a promising anode for high-performance LIBs. [Display omitted] [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO 2) has been considered as a promising anode material for alkaline ion batteries (AIBs), yet the low electrical conductivity and sluggish reaction kinetics have restricted its practical applications, while rational structure design can significantly overcome these drawbacks. Herein, we report a one-step fabrication of ultrafine anatase TiO 2 nanoparticles within holely carbon nanofibers (denoted as A-TiO 2 @HCNFs) via a facile electrospinning method and subsequent annealing treatment. The chemical reaction between TEOS (Si(OC 2 H 5) 4) and PVDF ((CH 2 CF 2) n) in the precursor induces the generation of numerous holes (via 4HF + SiO 2 = SiF 4 ↑+ 2 H 2 O) during the carbonization process by annealing in Ar at 800 °C, leading to the formation of holely structure and the suppression of the anatase-to-rutile phase transformation. When employed as anode materials for AIBs, the A-TiO 2 @HCNFs exhibit a high sodium storage capacity of 206.8 mAh g−1 at 1.0 A g−1 after 500 cycles and a superior rate performance of 188.4 mAh g−1 at 5.0 A g−1, and a lithium storage capacity is 354.0/233.9 mAh g−1 at 0.2/1.0 A g−1 after 100/500 cycles with an excellent rate performance of 145.6 mAh g−1 at 5.0 A g−1. The superior electrochemical performance is related to the unique structure with integration of ultrafine anatase TiO 2 nanoparticles and holely carbon nanofibers, which bring many advantages including improved electrical conductivity, sufficient reaction sites and robust structure stability. [Display omitted] • Template-free one-pot hole generation within carbon nanofibers is realized through chemical reaction between TEOS and PVDF. • Ultrafine anatase TiO 2 nanoparticles were produced and uniformly distributed within the holely carbon nanofibers. • The anatase TiO 2 nanoparticles within holely carbon nanofibers demonstrate excellent sodium and lithium storage performances. [ABSTRACT FROM AUTHOR]

Recently, electrospinning technology has high-potential applications in the large-scale manufacturing of one-dimensional (1D) nano-catalytic functional materials. Herein, Ni nanoparticles embedded within highly N-doped carbon nanofibers (Ni@NCNFs) were fabricated using polyacrylamide (PAM) and nickel acetate (NiAc) aqueous solutions as precursors by electrospinning and subsequent carbonization for the first time. The as-prepared Ni@NCNFs were smoothly applied to the hydrogenation of quinoline toward 1,2,3,4-tetrahydroquinoline and manifested excellent catalytic performance with extremely high selectivity (99.0%) at full conversion (99.3%). The influence factors on the physicochemical properties were further studied, including the carbonization temperature, the PAM mass fractions and the mole ratios between PAM and NiAc (PMA/Ni). The present work demonstrated that electrospinning and carbonization could be potential technologies for manufacturing Ni@NCNFs as an outstanding catalyst for quinoline hydrogenation. Furthermore, PAM rich in nitrogen could serve as a new alternative electrospinning precursor for future applications. [Display omitted] • Polyacrylamide was proved as an excellent electrospinning precursor loaded various metal, including Ni, Co and Cu. • Fibrous Ni@NCNFs with high N-doping were fabricated by electrospinning with subsequent carbonization. • Facilely prepared Ni@NCNFs manifested excellent catalytic performance in quinoline hydrogenation. • 99.0% of 1,2,3,4-tetrahydroquinoline selectivity was achieved at 99.3% of quinoline conversion. [ABSTRACT FROM AUTHOR]

• The carbon nanofiber coated cobalt sulfide nanoparticles with high N, S doping content could be synthesized with N 2 and CS 2 assistance. • N, S co-doped carbon reduces the diffusion barrier and enhances the adsorption of Li/Na ions. • The sample exhibits excellent reversible capacity for lithium/sodium storage. [Display omitted] In this work, N and S co-doped carbon nanofibers coated with cobalt sulfide nanoparticles (CoS x /N-SCFs) were synthesized by a simple method as anode materials for Li+/Na+ storage. The cobalt sulfide nanoparticles are uniformly embedded in carbon nanofibers in this composite, which effectively shortens the Li+/Na+ diffusion distance and buffers the volume expansion caused by discharge/charge. Besides, the doped N and S improve the conductivity of the carbon nanofibers and expand the carbon interplanar spacing, which facilitates the diffusion of Li+/Na+. The obtained CoS x /N-SCFs electrode shows an excellent reversible capacity of 761.3 mAh g−1 after 1000 cycles at 2 A g−1 for lithium storage and a reversible capacity of 505.1 mAh g−1 after 100 cycles at 100 mA g−1 for sodium storage. Density functional theory calculations further demonstrate that the N, S co-doping increases the electronic conductivity of carbon matrix and reduces Li+/Na+ diffusion barrier, thus effectively enhancing the adsorption of Li+/Na+. This work provides an effective method for synthesizing metal sulfide/carbon nanocomposites as high-performance anode materials. [ABSTRACT FROM AUTHOR]

• A feasible electrospinning strategy was proposed to construct a 1D/1D hierarchical superstructure. • NiS/NiO hetero-nanoparticles immobilized firmly in such hierarchical superstructures. • NiS/NiO@N-C NT/NFs demonstrate prominent OER performance in alkaline electrolyte. • The chemisorption energies of the oxygen-related intermediates are optimized by NiS/NiO heterojunction. Electronic regulation via interfacial engineering is a versatile strategy to boost the efficiency of earth-abundant electrocatalysts for the oxygen evolution reaction (OER). Herein, we demonstrate the combination of interfacial manipulation with nanoarchitectonics by elaborately designing Janus-structured NiS/NiO nanoparticles in-situ encapsulated within N-doped carbon nanotube "branches"/nanofiber "trunk"-typed superstructures (abbreviated as NiS/NiO@N-C NT/NFs hereafter) to effectively regulate the electronic configuration for expediating the OER process. The simultaneous realization of interfacial engineering and nanoarchitectonics renders the resultant NiS/NiO@N-C NT/NFs with optimized electronic configuration, increased oxygen vacancies, promoted mass diffusion channels and remarkable structural robustness. Therefore, the NiS/NiO@N-C NT/NFs exhibit outstanding OER activity with a small overpotential of 269 mV at 10 mA cm−2 and impressive long-term stability in alkaline electrolyte, representing an economical and competetive electrocatalyst for a number of sustainable energy devices. Density functional theory (DFT) simulations further validate that the formation of NiS/NiO heterojunction effectively tailors the chemisorption energies of the oxygen-related intermediates and reduces the reaction barrier, drastically accelating the OER kinetics. These findings demonstrating the significance of interface manipulation and hybridization with nanocarbon may offer a novel perspective for rational design of high-performance electrocatalysts towards the energy storage and conversion. [ABSTRACT FROM AUTHOR]

• Hierarchically porous nanofibers are prepared by electrospinning technique. • Nanofibers include core–shell Co 3 O 4 @graphitic carbon grafted within N-doped CNTs. • N-CNTs, graphitic carbon, and polar Co 3 O 4 ensure polysulfide trapping/reuse. • Li–S cell with unique structure-coated separator exhibits stable cycling property. Hierarchically porous nanofibers (NFs) comprising multiple core–shell Co 3 O 4 @graphitic carbon (GC) nanoparticles grafted within N-doped carbon nanotubes (CNTs) (Co 3 O 4 @GC/N-CNT NF) were rationally designed as functional interlayers for excellent Li–S batteries (LSBs). The well-grafted N-doped CNTs (N-CNTs) and high-conductivity GC layer coated on Co 3 O 4 nanoparticles provided conductive channels for fast ionic/electronic transfer during charging–discharging. The Co 3 O 4 nanoparticles inside the GC layer served as active polar sites for efficient anchoring of dissolved lithium polysulfides and ensured their reuse during redox reactions via fast charge transfer processes. Consequently, the assembled Li–S cell featuring a Co 3 O 4 @GC/N-CNT NF-coated separator and a pure sulfur electrode (70 wt% and 2.0 mg cm−2 loading) presented an excellent electrochemical performance, namely a high-rate capability and stable cycling performance at C-rates of 0.1, 0.5, and 1.0C. In addition, the Li-ion diffusion coefficient of the assembled Li–S cell (10−8 cm2 s−1) was one order of magnitude higher than those of the assembled Li–S cells featuring bare Co 3 O 4 NF-coated and pristine separators (10−9 cm2 s−1). The remarkable overall cell performance was attributed to the combination of highly conductive N-CNTs, GC layer, and polar Co 3 O 4 nanoparticles, which effectively trapped polysulfides. Therefore, we believe that the proposed unique nanostructure synthesis method can provide new insights into the development of sustainable and highly conductive polar materials as functional interlayers for advanced LSBs. [ABSTRACT FROM AUTHOR]

[Display omitted] One-dimensional (1D) electrospun carbon nanofibers functionalized with NiCo 2 S 4 nanoparticles have been synthesized and exhibits excellent performance as a low-cost, lightweight, flexible and binder-free cathode for aqueous Ni-Zn batteries. • Electrospun carbon nanofibers functionalized with NiCo 2 S 4 nanoparticles are synthesized. • The CNF@NiCo 2 S 4 electrode is lightweight, flexible and binder-free. • The CNF@NiCo 2 S 4 exhibits excellent performance for aqueous Ni-Zn batteries. • The quasi-solid-state CNF@NiCo 2 S 4 //Zn battery is also fabricated with polymer electrolyte. Aqueous nickel-zinc (Ni-Zn) batteries hold great promise for large-scale energy storage systems. However, traditional Ni-based cathode electrodes are generally consist of none capacity contribution additives and heavy current collectors, resulting in a low percentage of the active materials. In this regard, developing lightweight, flexible and binder-free cathode electrodes for aqueous Ni-Zn batteries is highly desirable. Herein, for the first time, we develop a simple electrospinning technique to synthesize the one-dimensional (1D) electrospun carbon nanofibers functionalized with ternary NiCo 2 S 4 nanoparticles (denoted as CNF@NiCo 2 S 4) as a lightweight, flexible and binder-free electrode for aqueous Ni-Zn batteries. Based on the self-standing CNF@NiCo 2 S 4 film as cathode, the as-fabricated aqueous CNF@NiCo 2 S 4 //Zn battery exhibits a high capacity of 0.32 mAh cm−2 and 35.9 mAh cm−3 at a current density of 2 mA cm−2, and good rate performance (0.21 mAh cm−2 at 20 mA cm−2) and long-term cycling stability (83% capacity retention at 10 mA cm−2 after 2000 cycles). More importantly, a quasi-solid-state CNF@NiCo 2 S 4 //Zn battery is also fabricated, which also displays an impressive energy density of 362.3 Wh kg−1, indicating the potential towards practical applications. Impressively, the volumetric energy density of CNF@NiCo 2 S 4 //Zn battery are 58.2 mWh cm−3 (liquid) and 45.4 mWh cm−3 (quasi-solid-state), which are much larger than the values of other reported Ni-Zn batteries. Theses results indicate the self-standing CNF@NiCo 2 S 4 film is promising for for next generation electronic applications. [ABSTRACT FROM AUTHOR]

We developed free-standing nitrogen-doped carbon nanofiber (CNF) electrodes incorporating Co/CoOx nanoparticles (NPs) as a new cathode material for removing Acid Orange 7 (AO7; a dye for wool) from wastewater by the heterogeneous electro-Fenton reaction. We produced the free-standing N-doped CNF electrodes by electrospinning a polyacrylonitrile (PAN) and cobalt acetate solution followed by thermal carbonation of the cobalt acetate/PAN nanofibers under a nitrogen atmosphere. We then investigated electro-Fenton-based removal of AO7 from wastewater with the free-standing N-doped-CNFs-Co/CoOx electrodes, in the presence or not of Fe2+ ions as a co-catalyst. The electrochemical analysis showed the high stability of the prepared N-doped-CNF-Co/CoOx electrodes in electrochemical oxidation experiments with excellent degradation of AO7 (20 mM) at acidic to near neutral pH values (3 and 6). Electro-Fenton oxidation at 10 mA/cm2 direct current for 40 min using the N-doped-CNF-Co/CoOx electrodes loaded with 25 wt% of Co/CoOx NPs led to complete AO7 solution decolorization with total organic carbon (TOC) removal values of 92.4% at pH 3 and 93.3% at pH 6. The newly developed N-doped-CNF-Co/CoOx electrodes are an effective alternative technique for wastewater pre-treatment before the biological treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • W 2 C/C NFs are fabricated by an electrospinning-assisted synthetic strategy. • Good HER activity for W 2 C/C NFs: η 10 of 92, 81, and 115 mV in acidic, alkaline, and neutral media. • HER activity of W 2 C/C NFs precede 20% Pt/C at high current density in 1.0 M KOH. As a promising electrocatalyst for the hydrogen evolution reaction (HER), ditungsten carbide (W 2 C) has aroused extensive attention. Pure-phase W 2 C nanoparticles embedded in carbon nanofibers (W 2 C/C NFs) could provide abundant accessible catalytically active sites and facilitate electron transfer for efficient HER. In this work, W 2 C/C NFs were fabricated by an electrospinning-assisted synthetic strategy. The optimized sample W 2 C/C NFs-20 exhibits excellent electrocatalytic performances in wide-pH range, especially in alkaline media, showing low overpotential (η) of 81, 137, and 157 mV to reach 10, 100, and 200 mA cm−2, respectively. One dimensional nanostructure and the strong coupling of W 2 C within the carbon matrix synergistically brought faster electron transport and more active sites, and thus a significant enhancement in HER activity. Based on the strategy reported here, other transition metal carbide nanofibers could be prepared to expand opportunities in various catalytic applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • W 2 C/C NFs are fabricated by an electrospinning-assisted synthetic strategy. • Good HER activity for W 2 C/C NFs: η 10 of 92, 81, and 115 mV in acidic, alkaline, and neutral media. • HER activity of W 2 C/C NFs precede 20% Pt/C at high current density in 1.0 M KOH. As a promising electrocatalyst for the hydrogen evolution reaction (HER), ditungsten carbide (W 2 C) has aroused extensive attention. Pure-phase W 2 C nanoparticles embedded in carbon nanofibers (W 2 C/C NFs) could provide abundant accessible catalytically active sites and facilitate electron transfer for efficient HER. In this work, W 2 C/C NFs were fabricated by an electrospinning-assisted synthetic strategy. The optimized sample W 2 C/C NFs-20 exhibits excellent electrocatalytic performances in wide-pH range, especially in alkaline media, showing low overpotential (η) of 81, 137, and 157 mV to reach 10, 100, and 200 mA cm−2, respectively. One dimensional nanostructure and the strong coupling of W 2 C within the carbon matrix synergistically brought faster electron transport and more active sites, and thus a significant enhancement in HER activity. Based on the strategy reported here, other transition metal carbide nanofibers could be prepared to expand opportunities in various catalytic applications. [ABSTRACT FROM AUTHOR]

In this work, we have developed a side by side nanofibers (SBS NFs) by a versatile electrospinning technique using a self-designed nozzle that allows the ejecting of the solution simultaneously in a side by side manner. The as-designed fiber was composed of Zinc oxide nanoparticles (ZnO NPs) on one side while silver nanoparticles (Ag NPs) on the other side, thereby forming a coupled fiber with a property of photo catalysis and antibacterial properties, respectively. The results showed enhanced dye degradation up to 97% within 140 min of test and antibacterial properties against gram-positive and gram-negative bacteria by the SBS NFs as compared to 80% degradation for the single nanofibers (SNFs) which had both ZnO NPs and Ag NPs but in a random orientation. SBS NFs filter (ZA-3) also exhibited a high filtration efficiency (80%) comparable to the lower 72% for SNFs filter. We believe that the as-modified electrospinning setup can be easily extended to prepare a new generation of nanofibers for a variety of applications such as biomedical, filtration, oil/water separation, and so on. [Display omitted] • A multifunctional membrane composed of side by side nanofibers is presented. • Proposed the air filter with enhanced antibacterial and photocatalytic ability. • ZnO NPs was accommodated onto one side of the fiber while Ag NPs onto other side. • Side by side nanofibrous membrane had high air filtration. [ABSTRACT FROM AUTHOR]

● Hollow Co 3 O 4 anchored in porous carbon nanofibers is designed as anode for Na+ storage. ● The hollow structure shortens the ion transport path for fast reaction kinetics. ● The porous carbon facilitates electron/ion transport and guarantees structural stability. ● Superior electrochemical performance are achieved in both half-cells and full-cells. [Display omitted] Transition metal oxides with high theoretical specific capacity, when used as anode materials in sodium-ion batteries, usually suffer from poor structural stability and inferior rate capacity. The use of hollow nanostructured metal oxides incorporated into porous carbon frameworks is a promising strategy for addressing this issue. Herein, we fabricated hollow Co 3 O 4 nanoparticles anchored in a porous carbon nanofiber matrix (Co 3 O 4 @PCNF) by electrospinning, metal–organic framework incorporation, and two-step calcination. The porous carbon nanofiber matrix can facilitate structural stability and provide multiple channels for fast electron/ion transport. The hollow Co 3 O 4 nanoparticles resulting from the Kirkendall effect can shorten the Na-ion transport path for achieving fast reaction kinetics. The Co 3 O 4 @PCNF exhibits a reversible specific capacity of 487 mAh g−1 at 0.05 A g−1 with a high initial Coulombic efficiency of 91.6%, outstanding rate performance (220 mAh g−1 at 5 A g−1), and stable cycling, thereby making it suitable as an anode for sodium-ion batteries. Moreover, a full cell fabricated using a Co 3 O 4 @PCNF anode and Na 3 V 2 (PO 4) 2 O 2 F cathode delivers a reversible capacity of 205 mAh g−1 at 0.5 A g−1. We believe that our approach can provide a design pathway to improve the performance of Co 3 O 4 -based anodes for sodium-ion batteries and offer a new strategy to produce hollow-structure electrode materials for other energy-storage devices. [ABSTRACT FROM AUTHOR]

• CoNi alloy nanocrystals were synthesized on electrospun N-doped Carbon Nano Fibers. • The strong synergetic behavior between Co and Ni via alloying improved and optimized the electrochemical performance of catalysts. • This research provides a feasible method for designing self-supporting alloy catalysts. Alloying, a general strategy to improve the electrocatalytic performance of non-precious metal catalysts. Herein, we adopt a simple method to in-situ grow a cobalt-nickel alloy on a three-dimensional network of N-doped carbon fibers that put spatial restriction to the alloy particles, making the size smaller and uniformly distributed. The electronic synergy between nickel and cobalt and the confinement effect of in-situ growth can make Co-Ni/NCNFs provide more feasible reaction sites for catalytic hydrogen evolution reaction. Simultaneously, the formation of cobalt-nickel alloys inhibits the generation of oxides during the synthesis process, so as to promote the quality of alloys with better activity. Co-Ni/NCNFs exhibits excellent electrocatalytic properties with only 61 mV overpotential and 152.3 dec−1 at 10 mA cm−2 current density and excellent long-term stability due to the in-situ growth approach. This research also provides a feasible method for designing self-supporting alloy catalysts by in-situ growth. [ABSTRACT FROM AUTHOR]