Carbon Nanofiber Matrix Research Articles

Flexible electrospun porous carbon nanofiber@PEG phase change nanofibrous membrane for advanced solar-/electro-thermal energy conversion and storage

Flexible phase change materials (PCMs) showed great application prospects in the field of thermal management of flexible electronic devices and wearable devices, nevertheless, their development was seriously hindered by the intrinsic solid rigidity, liquid leakage and lack of functionality of PCMs. Herein, a multifunctional flexible leakage-proof composite PCM (named PCNF@PEG) was fabricated, in which poly(ethylene glycol) (PEG) was encapsulated in robust flexible porous carbon nanofibers (PCNFs) derived from electrospun polyacrylonitrile/polystyrene (PAN/PS) composite nanofibers. The as-prepared PCNF@PEG showed excellent flexibility, shape stability, satisfactory phase change performance with melting/freezing latent heat of 71.9/70.9 J g−1 and prominent thermal reliability after 100 thermal cycles. Moreover, the thermal conductivity of PCNF@PEG was noticeably enhanced by 45 % compared to pure PEG. Significantly, the interconnect carbon nanofiber matrix endowed PCNF@PEG unprecedented solar-/electro-thermal energy conversion performance and cycle stability. Therefore, the fabricated PCNF@PEG with pronounced comprehensive performance is a promising candidate for advanced thermal management applications in flexible devices.

Novel electrochemical sensing platform based on zinc metal organic frameworks/carbon nanofiber nanocomposite for detection of creatinine in human urine

A biomarker known as creatinine is a very important determinant of kidney failure. Creatinine concentrations in blood and urine can identify renal insufficiencies and muscle diseases. Monitoring the creatinine level and quick sensing requires a rapid, robust and simple method for determining the creatinine in human body. To overcome the universal challenge postured by this waste product of muscle, this study presents a novel strategy to fabricate an electrochemical sensor based on zinc MOFs, synthesized using terephthalic di- hydrazide (TPDD) as the organic ligand using a one-pot solvothermal method in the presence of carbon nanofiber matrix for enzyme less sensing the creatinine. The Zn-TPDD/CNF nanocomposite was well characterized by XRD, TGA, BET, XPS, FESEM, CV, DPV, and Raman spectroscopic techniques. Notably, this MOF anchored electrode owns important fundamental features such as large electro active exterior area, plentiful active sites, an immense operational linear range (5 to 250 μM), a nominal detection limit (10.04 nM), and an outstanding sensitivity towards creatinine. This Zn-TPDD/CNF/GCE electrode not only showcased more extraordinary electrochemical attributes, but its anti-interference stability, flexibility, reproducibility, storage stability, selectivity, and low detection threshold emphasize its ability for real-world applications with reasonable recoveries. Therefore, this modified electrode could be a potential tool for operative creatinine detection in urine.

Empowering Low-Temperature Lithium-Sulfur Batteries: Unlocking the Potential of Transition Metal Alloy-Based Cathode Materials.

At low temperatures, lithium-sulfur (Li-S) batteries have poor kinetics, resulting in extreme polarization and decreased capacity. In this study, we investigated the electrochemical performance of Li-S batteries utilizing transition metal alloy-based cathode materials. Specifically, binary transition metal alloys (FeNi, FeCo, and NiCo) are integrated into a porous carbon nanofiber (CNF) matrix as composite cathode material. Our findings reveal that alloying metallic Ni with Fe in the FeNi@CNFs composite enhances the catalytic conversion of sulfur species, mitigating the shuttle effect and improving battery performance even under low temperatures. Li-S batteries employing a Li2S6/FeNi@CNFs cathode exhibited a significantly high initial discharge capacity of 1655 mAh g-1 at 0.1 C. Even at the higher current density of 10 C, the Li2S6/FeNi@CNFs composite can still reach an ultrahigh specific capacity of 828 mAh g-1. In addition, Li2S6/FeNi@CNFs demonstrated exceptional initial discharge capacities of 890.5 and 382.7 mAh g-1 at 0.1 C under -20 and -40 °C, respectively. With an initial capacity of 392.02 mAh g-1 and a capacity retention rate of 88.86% (after 60 cycles) at 0.2 C, the conversion of LiPSs in Li2S6/FeNi@CNFs is significantly enhanced even at ultralow temperatures of -40 °C. The findings of this study hold significant implications for the advancement of extremely low-temperature Li-S batteries.

Iron metal organic framework decorated carbon nanofiber-based electrode for electrochemical sensing platform of chlorpyrifos in fruits and vegetables

Chlorpyrifos, a prime insecticide encountered in numerous agricultural products, is associated with an array of adverse health implications, notably endocrine disturbances and carcinogenic tendencies. Monitoring the environment and controlling quality requires a rapid and simple method for determining the organophosphate insecticide. Overcome the universal challenge postured by this contaminant, this study presents a novel strategy to fabricate an electrochemical sensor based on Iron MOFs, synthesized using 3,5-pyrazoledicarboxylic acid (PyDA) using one-pot solvothermal method with carbon nanofiber matrix for sensing the chlorpyrifos. Notably, this MOF anchored electrode owns important fundamental features such as an expansive surface area, abundant active sites, a vast operational spectrum linear range (1.0–150 μM), a minimal detection threshold (15.1 nM), and an amplified sensitivity towards chlorpyrifos. This Fe-PyDA/CNF/GCE electrode not only showcased more extraordinary electrochemical attributes, but its broad linear detection range and low detection threshold emphasize its ability for real-world applications with reasonable recoveries.

Effect of synthesized copper oxide nanorods on electrical and thermal properties of compatibilized high‐density polyethylene/carbon nanofiber nanocomposite films

AbstractHigh‐density polyethylene (HDPE) nanocomposites containing different optimized fractions of carbon nanofiber (CNF) at 6 wt.%, polyethylene glycol (PEG) at 4 wt.%, and copper oxide (CuO) nanorods in concentration ranges of 0.15, 0.5, and 2 wt.% were successfully melt processed using corotating twin extrusion and compression molding technique. The effect of PEG and CuO nanofiller on the HDPE matrix were studied, particularly for the percolation threshold for electrical conductivity, structural morphology, and other properties including thermal stability, thermal conductivity (TC), dielectric, and UV protection properties. It is observed that PEG acts as a good compatibilizer, facilitating better interfacial connection between CNF and HDPE matrix. The optimized composite with 0.15 wt.% CuO nanorods (H/C6/P4/Cu0.15) shows a fine morphology and strong interfacial connections between fillers and the matrix, as observed in FE‐SEM micrographs. This optimized composite exhibits improved thermal stability, higher thermal conductivity (0.0404 W.K−1.m−1), increased dielectric constant, reduced electrical volume resistivity (from 2.1 × 1015 to 2.1 × 106 Ω.cm), and lower optical band gap value (2.74 eV). Additionally, all prepared nanocomposites offer approximately 100% Ultraviolet Protection Factor (UPF) rating for UV protection.Highlights The transformation of insulating HDPE into conducting HDPE composites. The effect of CuO nanorods was investigated in compatibilized HDPE composites. A percolation is achieved in the HDPE composite at 0.15 wt.% of CuO nanorods. PEG and CuO nanorods improved the multifunctional properties of the composite.

Design of Na3MnZr(PO4)3/Carbon Nanofiber Free-Standing Cathodes for Sodium-Ion Batteries with Enhanced Electrochemical Performances through Different Electrospinning Approaches.

The NASICON-structured Na3MnZr(PO4)3 compound is a promising high-voltage cathode material for sodium-ion batteries (SIBs). In this study, an easy and scalable electrospinning approach was used to synthesize self-standing cathodes based on Na3MnZr(PO4)3 loaded into carbon nanofibers (CNFs). Different strategies were applied to load the active material. All the employed characterization techniques (X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), thermal gravimetric analysis (TGA), and Raman spectroscopy) confirmed the successful loading. Compared to an appositely prepared tape-cast electrode, Na3MnZr(PO4)3/CNF self-standing cathodes demonstrated an enhanced specific capacity, especially at high C-rates, thanks to the porous conducive carbon nanofiber matrix. Among the strategies applied to load Na3MnZr(PO4)3 into the CNFs, the electrospinning (vertical setting) of the polymeric solution containing pre-synthesized Na3MnZr(PO4)3 powders resulted effective in obtaining the quantitative loading of the active material and a homogeneous distribution through the sheet thickness. Notably, Na3MnZr(PO4)3 aggregates connected to the CNFs, covered their surface, and were also embedded, as demonstrated by TEM and EDS. Compared to the self-standing cathodes prepared with the horizontal setting or dip-drop coating methods, the vertical binder-free electrode exhibited the highest capacity values of 78.2, 55.7, 38.8, 22.2, 16.2, 12.8, 10.3, 9.0, and 8.5 mAh/g at C-rates of 0.05C, 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, 10C, and 20C, respectively, with complete capacity retention at the end of the measurements. It also exhibited a good cycling life, compared to its tape-cast counterpart: it displayed higher capacity retention at 0.2C and 1C, and, after cycling 1000 cycles at 1C, it could be further cycled at 5C, 10C, and 20C.

A flexible plane-wire MoO2-anchored carbon nanofiber matrix as freestanding anodes for lithium storage with enhanced cyclability

Inspired by beds of silkworm cocoon, a flexible ″plane-wire″ MoO2-anchored carbon nanofiber matrix has been successfully prepared through electrospinning and subsequent annealing processes. It delivers an initial discharge capacity of 877 mAh g−1 at 200 mA g−1 with a high initial coulombic efficiency of 84.7 % and showcases a high reversible specific capacity of 743 mAh g−1 in the second cycle when employed as free-standing anodes for lithium batteries. It also exhibits good rate performance and superb cyclability, which delivering a specific capacity of 364 mAh g−1 at a high current density of 2 A g−1 and maintains a notable specific capacity of 674 mAh g−1 even after 2000 cycles. It is found that, the carbon nanofiber matrix serves as a robust electronic conductive network to reduce the charge transfer resistance and promote the transportation of Li+, and provides excellent support to buffer volume changes of the MoO2, resulting in enhanced rate performance and cyclability. Moreover, these electrodes are designed to be free-standing, which can improve the flexibility of the electrode and initial coulombic efficiency. It is believed that the as-prepared ″plane-wire″ MoO2-anchored carbon nanofiber matrix is a promising anode material for high-performance LIBs.

ZnSe/SnSe Heterostructure Incorporated with Selenium/Nitrogen Co-Doped Carbon Nanofiber Skeleton for Sodium-Ion Batteries.

Effective strategies toward building exquisite nanostructures with enhanced structural integrity and improved reaction kinetics will carry forward the practical application of alloy-based materials as anodes in batteries. Herein, a free-standing 3D carbon nanofiber (CNF) skeleton incorporated with heterostructured binary metal selenides (ZnSe/SnSe) nanoboxes is developed for Na-ion storage anodes, which can facilitate Na+ ion migration, improve structure integrity, and enhance the electrochemical reaction kinetics. During the carbonization and selenization process, selenium/nitrogen (Se/N) is co-doped into the 3D CNF skeleton, which can improve the conductivity and wettability of the CNF matrices. More importantly, the ZnSe/SnSe heterostructures and the Se/N co-doping CNFs can have a synergistic interfacial coupling effect and built-in electric field in the heterogeneous interfaces of ZnSe/SnSe hetero-boundaries as well as the interfaces between the CNF matrix and the selenide heterostructures, which can enable fast ion/electron transport and accelerate surface/internal reaction kinetics for Na-ion storage. The ZnSe/SnSe@Se,N-CNFs exhibit superior Na-ion storage performance than the comparative ZnSe/SnSe, ZnSe and SnSe powders, which deliver an excellent rate performance (882.0, 773.6, 695.7, 634.2, and 559.0mAhg-1 at current rates of 0.1, 0.2, 0.5, 1, and 2Ag-1) and long-life cycling stability of 587.5mAhg-1 for 3500 cycles at 2Ag-1.

Tailored synthesis and optimization of nickel-molybdenum carbide-graphite nanofiber composite for enhanced ethanol electrooxidation.

A novel nickel-molybdenum carbide-graphite nanofiber composite is introduced as an electrocatalyst for ethanol electrooxidation. The proposed nanofibers have been prepared by calcinating electrospun nanofibers composed of nickel acetate tetrahydrate, molybdenum chloride, and polyvinyl alcohol. The calcination process was conducted at different temperatures (700, 850, and 1000°C) under a nitrogen gas atmosphere with a heating rate of 2.5 deg/min and a holding time of 5 h. Physicochemical characterizations have indicated that nickel acetate is entirely reduced to nickel metal during the sintering process, and molybdenum has bonded with carbon to produce molybdenum carbide. At the same time, the used polymer has been pyrolyzed to produce a carbon nanofiber matrix embedding formed inorganic nanoparticles. Electrochemical measurements concluded that molybdenum content and calcination temperature should be controlled to maximize the electrocatalytic activity of the proposed catalyst. Typically, the oxidation peak current density was 28.5, 28.8, 51.5, 128.3, 25.6, and 3 mA/cm2 for nanofibers prepared from an electrospun solution containing 0, 5, 10, 15, 25, and 35 wt% molybdenum carbide, respectively. Moreover, it was observed that increasing the calcination temperature distinctly improves the electrocatalytic activity. Kinetic studies have indicated that the reaction order is close to zero with a reaction temperature-dependent value. Moreover, it was detected that the electrooxidation reaction of ethanol over the proposed nanofiber composite follows the Arrhenius equation. The determined activation energy is 33 kJ/mol, which indicates good catalytic activity for the introduced nanofibers. Through the application of a set of visualization-based tools and the general linear model (GLM), the optimal conditions that generate the highest current density were identified. The computations unveiled that the optimal parameter settings are as follows: Mo content at 15 wt.%, methanol concentration of 1.55 M, and reaction temperature of 59°C.

Signal Amplification for Detection of Nilutamide in Three-Dimensional Electrochemical Sensor Using Copper Metal–Organic Framework Decorated Carbon Nanofibers

The extensive use of antibiotics has rapidly spread antibiotic resistance, which poses significant health risks to humans. Unfortunately, despite this pressing issue, there is still a lack of a reliable on-site detection method for the residues of antibiotics, such as nilutamide (Nlu). Consequently, there is an urgent need to develop and perfect such a detection method to effectively monitor and control antibiotic residues. In this study, the hydrothermal development of copper-metal-organic framework (Cu-MOF) polyhedrons on the functionalized carbon nanofiber (f-CNF) matrix allowed for the detection of Nlu in biological liquids via a sensitive amperometry technique. Further electrochemical detection of Nlu took place with the cyclic voltammetry (CV) technique Cu-MOF/f-CNF. Analytical and spectroscopic approaches were used to confirm the successful synthesis of Cu-MOF/f-CNF. The prepared material was decorated on the surface of GCE and performed as an electrochemical Nlu sensor, with a broad linear range of 0.01 to 141.4 μM and 2 nM as a lower limit of detection. In addition, the composites had a large surface area and many dedicated sites, which improved electrocatalysis. In practical applications, Cu-MOF/f-CNF/GCE provides a novel strategy for improving electrochemical activity by measuring Nlu concentrations in biological samples.

Synthesis of Free-Standing Tin Phosphide/Phosphate Carbon Composite Nanofibers as Anodes for Lithium-Ion Batteries with Improved Low-Temperature Performance.

Free-standing tin phosphide/phosphate carbon composite nanofiber mats of unique nanostructure have been successfully synthesized by electrospinning and partially reducing the phosphate-containing precursors. An unusual effect of the Sn:P molar ratio in the precursor solution on the structure and physical-electrochemical properties of the material is observed. Physical characterizations, including X-Ray diffraction (XRD), Raman spectroscopy, X-Ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), confirm the formation of tin phosphide/phosphate nanoparticles of P-rich inner Snx P layer and Sn-rich outer layer uniformly distributed within carbon nanofiber matrix when the Sn:P=1:1. The prepared material is tested as an anode material for lithium-ion batteries and it retains 1141 mAh g-1 charge capacity after 300 cycles at a current density of 250mA g-1 with almost 100% Coulombic efficiency at room temperature. Furthermore, it demonstrates six times higher capacity (846 mAh g-1 ) at 0°C compared to a commercial graphite anode and stable cyclability at -20 °C and 50mA g-1 . Post-mortem ex situ XRD and SEM analyses confirm the structural stability of the designed material and the formation of a uniform stable solid electrolyte interphase layer even after 100 cycles at 50mA g- 1 .

Molybdenum Carbide/Ni Nanoparticles Embedded into Carbon Nanofibers as an Effective Non-Precious Catalyst for Green Hydrogen Production from Methanol Electrooxidation.

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.

Defect-engineered Sulfur Vacancy Modified NiCo2 S4-x Nanosheet Anchoring Polysulfide for Improved Lithium Sulfur Batteries.

The low conductivity of sulfur and the shuttle effect of lithium polysulfides (LiPSs) are the two intrinsic obstacles that limit the application of lithium-sulfur batteries (LSBs). Herein, a sulfur vacancy introduced NiCo2 S4 nanosheet array grown on carbon nanofiber (CNF) membrane (NiCo2 S4-x /CNF) is proposed to serve as a self-supporting and binder-free interlayer in LSBs. The conductive CNF skeleton with a non-woven structure can effectively reduce the resistance of the cathode and accommodate volume expansion during charge-discharge process. The bonding between CNF matrix and NiCo2 S4 nanosheet is enhanced by in situ growth, ensuring fast electron transfer. Besides, the sulfur vacancies in NiCo2 S4 enhance the chemisorption of LiPSs, and the highly active sites at vacancies can accelerate the LiPSs conversion kinetics. LSB paired with NiCo2 S4-x /CNF interlayer achieved improved stability in 500 cycles at 0.2 C and long life of 3000 cycles at 3 C. More importantly, a high areal capacity of 9.69 mAh cm-2 is achieved with a sulfur loading of 10.8mg cm-2 and a low electrolyte to sulfur (E/S) ratio of 4.8. This work provides insight into the sulfur vacancy in catalysis design for LiPSs conversion and demonstrates a promising direction for electronic defect engineering in material design for LSBs.

Binder-free Ruthenium Oxide/MXene/Carbon Nanofiber Ternary Composite Electrode for Supercapacitors

Carbon nanofiber-based electrodes are generally embedded with either metal oxides or two-dimensional materials to enhance their specific capacitance and rate performance. For the first time in this study, a flexible carbon nanofiber electrode consisting of metal oxide (RuO2) and two-dimensional MXene was prepared to realize the synergetic effect on the electrochemical performance. This ternary composite electrode was prepared by electrospinning RuO2, and MXene dispersed polyacrylonitrile precursor solution, followed by thermal treatment. The distribution of RuO2 nanoparticles and delaminated MXene sheets within a carbon nanofiber matrix was examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM), while morphological analysis was carried out using scanning electron microscopy (SEM). The electrode with pseudocapacitive RuO2 and layered MXene facilitated charge storage by faradic reactions and intercalation of electrolyte ions. Electrochemical studies demonstrated that the prepared ternary composite electrodes exhibit a specific capacitance of 322 F g−1 with a capacitance retention of 90% after 2500 cycles at 1 A g−1. Additionally, the ternary composite showed an excellent rate capability with a minimal drop in capacitance when the current density was varied from 2 A g−1 to 10 A g−1.

Molybdenum carbide/Ni nanoparticles-incorporated carbon nanofibers as effective non-precious catalyst for urea electrooxidation reaction

In this study, molybdenum carbide and carbon were investigated as co-catalysts to enhance the nickel electro-activity toward urea oxidation. The proposed electrocatalyst has been formulated in the form of nanofibrous morphology to exploit the advantage of the large axial ratio. Typically, calcination of electropsun polymeric nanofibers composed of poly(vinyl alcohol), molybdenum chloride and nickel acetate under vacuum resulted in producing good morphology molybdenum carbide/Ni NPs-incorporated carbon nanofibers. Investigation on the composition and morphology of the proposed catalyst was achieved by XRD, SEM, XPS, elemental mapping and TEM analyses which concluded formation of molybdenum carbide and nickel nanoparticles embedded in a carbon nanofiber matrix. As an electrocatalyst for urea oxidation, the electrochemical measurements indicated that the proposed composite has a distinct activity when the molybdenum content is optimized. Typically, the nanofibers prepared from electrospun nanofibers containing 25 wt% molybdenum precursor with respect to nickel acetate revealed the best performance. Numerically, using 0.33 M urea in 1.0 M KOH, the obtained current densities were 15.5, 44.9, 52.6, 30.6, 87.9 and 17.6 mA/cm2 for nanofibers prepared at 850 °C from electropsun mats containing 0, 5, 10, 15, 25 and 35 molybdenum chloride, respectively. Study the synthesis temperature of the proposed composite indicated that 1000 °C is the optimum calcination temperature. Kinetic studies indicated that electrooxidation reaction of urea does not follow Arrhenius’s law.

Protein-assisted bendable Cu-free anode: Hydroxy-functionalized mesoporous carbon matrix for flexible Li-ion batteries

Several approaches have been proposed for development of a current collector-free bendable energy storage electrode for flexible lithium-ion battery applications, such as construction of a hybrid composite structure and introduction of a simple synthesis procedure. However, a more fundamental strategy is required to achieve a highly bendable electrode using carbonaceous materials. We report a novel strategy for development of a protein-assisted bendable Cu-free anode using a hydroxy-functionalized mesoporous carbon nanofiber (CNF) matrix. Zinc oxide nanoparticles and glutamic acid were used as modification agents during the preparation of CNFs and mesoporous CNF structure with N dopants and rich hydroxy groups (Glu-PCNF). The resultant Glu-PCNF electrode exhibited competitive Li-ion storage capabilities, such as a high specific capacity of 469.87 mAh/g at a current density of 100 mA/g and fast energy storage (113.6 mAh/g at 2,000 mA/g). Moreover, the Glu-PCNF electrode maintained its energy storage performance after 1,000 cycles of bending, which demonstrates its high bendability. Therefore, the Cu-free Glu-PCNF electrode, with a high bendability and competitive energy storage performance, can accelerate the implementation of next-generation electronic devices with wearable and flexible functions.

Electrospun NiMoO4-encapsulated carbon nanofibers electrodes for advanced supercapacitors

NiMoO4-encapsulated carbon nanofiber (NiMoO4/ECNFs) composites have been synthesized successfully using electrospinning method and subsequent thermal treatments. The prepared specimens were examined using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), thermal gravimetric analyzer (TGA), and Fourier transform infrared spectroscopy (FTIR). Electrochemical measurements including cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) were performed on the symmetric supercapacitors (SSCs) which were assembled from the (75 %)NiMoO4/ECNFs binder-free nanostructured electrodes. Morphological and structural investigations revealed an open 3D interconnected conductive and grain-like texture with homogeneously dispersed monoclinic NiMoO4 nanoparticles. Moreover, a high specific capacity of 122.5 Fg−1 at 1 Ag−1 and an excellent energy density of 43.9 Whkg−1 at a power density of 1567.9 Wkg−1 were obtained from the SSCs. The constructed devices also delivered outstanding cyclic stability (92 % retention after 3000 cycles). The observed electrochemical properties have been ascribed to the uniform dispersion of nanoparticles in the conductive carbon nanofiber matrix. The results suggest that as-fabricated NiMoO4/ECNFs can be considered as a promising electrode material for high-performance supercapacitors.

Encapsulating Sn-Cu alloy particles into carbon nanofibers as improved performance anodes for lithium-ion batteries

The SnCu-SiO2 @CNFs composite nanofibers are successfully fabricated by electrospinning and subsequent heat treatments, in which the Sn-Cu alloy particles are uniformly confined in carbon nanofibers (CNFs) in the presence of SiO2. The characterization results show that incorporating SiO2 into the CNFs matrix can mitigate the problem of the phase separation between Sn-Cu alloy particles and CNFs and increase the fibrous structural integrity of the composite electrodes. Importantly, the SnCu-SiO2 @CNFs-1.0 composite electrode displays the improved electrochemical performance when the amount of Cu(Ac)2 is controlled at 1.0 mmol, in which the discharge specific capacity of the electrode not only delivers 501.8 mAh/g after 100 cycles at 100 mA/g, but also retains 467.4 mAh/g after rate cycles when the current density is abruptly recovered to 100 mA/g. Moreover, the SnCu-SiO2 @CNFs-1.0 electrode can possess an enhanced Li+ diffusion coefficient of approximately 1.58 × 10−16 cm2 s−1 and a high Warburg coefficient of 568.9 Ω cm2 s−0.5 at room temperature. The enhanced electrochemical performance can be partly ascribed to the complete encapsulation of Sn-Cu alloy particles by the CNFs matrix, and partly to the promotion of the over-all electronic conductivity. Furthermore, the flexible and conductive CNFs matrix and the stable Cu6Sn5 phase can conjoinedly accommodate the volume change of the electrodes during charge/discharge processes. Therefore, the facile strategy for encapsulating Sn-Cu alloy particles into CNFs may offer some a prospective instruction for the alloy anodes in the field of energy storage.

Tailoring the Void Space Using Nanoreactors on Carbon Fibers to Confine SnS2 Nanosheets for Ultrastable Lithium/Sodium-Ion Batteries.

Herein, a rational design of SnS2 nanosheets confined into bubble-like carbon nanoreactors anchored on N,S doped carbon nanofibers (SnS2 @C/CNF) is proposed to prepare the self-standing electrodes, which provides tunable void space on carbon fibers for the first time by introducing hollow carbon nanoreactors. The SnS2 @C/CNF provides the stable support with greatly enhanced ion and electron transport, alleviates aggregation and volume expansion of SnS2 nanosheets, and promotes the formation of abundant exposed edges and active sites. The volume balance between SnS2 nanosheets and hollow carbon nanoreactors is reached to accommodate the expansion of SnS2 during cycles by controlling the thickness of SnO2 shells, which achieves the best space utilization. The doping of N,S elements enhances the wettability of the carbon nanofiber matrix to electrolyte and Li ions and further improves the electrical conductivity of the whole electrode. Thus, the SnS2 @C/CNF benefits greatly in structural stability and pseudocapacitive capacity for improved lithium/sodium storage performance. As a result of these improvements, the self-standing SnS2 @C/CNF film electrodes exhibit the highly stable capacity of 964.8 and 767.6 mAh g-1 at 0.2 A g-1 , and excellent capacity retention of 87.4% and 82.4% after 1000 cycles at high current density for lithium-ion batteries and sodium-ion batteries, respectively.

Fabrication of N, S co-doped carbon nanofiber matrix with cobalt sulfide nanoparticles enhancing lithium/sodium storage performance

In this work, N and S co-doped carbon nanofibers coated with cobalt sulfide nanoparticles (CoSx/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 CoSx/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.