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Currently, lightweight wearable energy storage devices are in great demand owing to their use in wearable electronics and energy-efficient electric vehicles. Freestanding carbon nanofibers replace the need for metal substrates while providing a rapid electrical network owing to their excellent electrical properties. Bimetallic oxides with multivalent oxidation states facilitate the rapid transfer of electrolytic ions owing to efficient Faradaic reactions, thereby enhancing the overall energy storage capability. In this study, CoOx@CNF was derived from ZIF-67 (zeolitic-imidazolate framework) @PAN-2MI fibers that were stabilized in air at 280°C and then annealed in argon at 900°C. Subsequently, Co was seeded on the annealed CoOx@CNF and subjected to a hydrothermal process in sodium molybdate dihydrate solution to grow CoMoO4 nanosheets, eventually forming bimetallic CoMoO4@CNF. The concentration of sodium molybdate solution was varied to determine the optimal growth conditions for CoMoO4 nanosheets. The energy density of the optimal bimetallic CoMoO4@CNF sample was 166.5 μWh cm-2 at a power density of 200 μW cm-2; this represented a nearly twofold increase compared to that of the single metallic CoOx@CNF. Powering humidity sensors using only one CoMoO4@CNF supercapacitor was demonstrated. The optimal sample remained stable during long-term galvanostatic charge and discharge cycles ( N cyc = 30,000) and retained 100% of its specific capacitance. [ABSTRACT FROM AUTHOR]

Summary: Flexible, lightweight, and freestanding zinc‐manganese oxide carbon nanofibers are promising materials for the fabrication of portable electronic devices. Composite nanofibers were synthesized using terephthalic acid and sodium dodecyl sulfate. Terephthalic acid improves the flexibility of the composite fibers and facilitates the diffusion of electrolytic ions. Meanwhile, sodium dodecyl sulfate aids to elevate the metal (zinc) oxide particles to the surface of the nanofibers during annealing. The texturing of the carbon nanofiber surface with ZnO enhances the electrochemical activity of the composite fibers. Parametric studies were conducted by varying the weight ratio of zinc and manganese acetates from zero to unity. The optimal case with a ratio of 0.75 produces specific capacitances of 1080 and 817 F·g−1 at current densities of 1 and 10 A·g−1, respectively, with a wide potential window of 1.6 V, indicating outstanding energy storage capabilities. The capacitance retention was 92% after 10 000 galvanostatic charge‐discharge cycles. The bending angle test confirmed the mechanical durability of the freestanding carbon nanofiber electrodes, and the corresponding change in the cyclic voltammetry curve was negligible. [ABSTRACT FROM AUTHOR]

Electrospinning technique is a simple and cheap method for fabrication of electrospun nanofibers (ENFs), which in turn can converted into electrospun carbon nanofibers (ECNFs) by carbonization process. The controlling of the ECNFs properties (e.g. surface area, porosity, diameters) during fabrication, make it superior over the other carbon nanomaterials. The aim of our study is to modify the surface of ECNFs to increase its hydrophilicity and in turn its efficiency in removing lead ions (Pb2+) from aqueous systems. The surface modification was carried out in two steps starting from oxidation of pristine ECNFs to produce oxidized ECNFs (o-ECNFs), followed by covalently bonded of melamine, and poly(m-phenylene diamine) for forming melamine-functionalized ECNFs (melam-ECNFs) and poly(m-phenylene diamine)-functionalized ECNFs (PmPDA-ECNFs), respectively. The as-prepared materials were characterized in routine way. The ability of the as-prepared materials towards adsorption of Pb2+ ions as heavy metal was investigated with the study of some factors such as pH solution, contact time, initial concentration and temperature. The adsorption process was analyzed isothermally, and kinetically. According to the values of the thermodynamic parameters, the adsorption of Pb2+ ions onto the functionalized ECNFs was endothermic and spontaneous, except with melam-ECNFs was exothermic. [ABSTRACT FROM AUTHOR]

• Enhancing the adsorption performance of electrospun carbon nanofibers (ECNFs) via functionalization process. • ECNFs were functionalized using ethylene diamine, p-phenylene diamine, diamino pyridine and melamine. • DAPy-ECNFs is the most efficient adsorbent within the prepared amine-functionalized ECNFs. • Adsorption kinetics, isotherms, and thermodynamics were investigated in detail. Electrospun carbon nanofibers (ECNFs) are hydrophobic materials and have inadequate dispersion in aqueous media. To solve this problem and sustain their applications in removing ionic pollutants, this study focuses on changing their nature to hydrophilic via surface functionalization using various amine-containing compounds such as ethylene diamine (EDA), p -phenylenediamine (PDA), 2,6-diaminopyridine (DAPy) and melamine (melam). These compounds can be grafted onto oxidized ECNFs (O-ECNFs) through amidation reaction, thus forming amine-functionalized electrospun carbon nanofibers (ECNFs-NH 2). The morphology and structure of the prepared adsorbents were investigated using routine analysis. ECNFs-NH 2 was applied for the removal of cationic dye and the obtained results showed that the adsorption capacity of ECNFs-NH 2 was dependent on the type of amine agent. Moreover, the isotherm and kinetic studies of MB removal by ECNFs-NH 2 followed Redlich-Peterson and pseudo-second order model, respectively. Adsorption mechanism of MB onto the surface of ECNFs-NH 2 was proposed and calculated in terms of thermodynamic parameters. [ABSTRACT FROM AUTHOR]

The use of some hydrogels as adsorbents for pollutants removal from wastewater is limited due to their high swelling properties and the difficulty in recovering them after the adsorption process. To overcome these problems, a new hydrogel nanocomposite based on chitosan-grafted-polyacrylic acid/oxidized electrospun carbon nanofibers (CT-g-PAA/O-ECNFs) was prepared by an in situ grafting polymerization process. The prepared hydrogel nanocomposite was used as a novel effective and highly reusable adsorbent for the removal of methylene blue (MB) from polluted water with low cost. The morphology and the structure of CT-g-PAA/O-ECNFs were investigated by numerous techniques. The effect of incorporating O-ECNFs on the swelling capability of the prepared hydrogel was explored in distillated water and MB solution at normal pH. The effect of parameters including ratio of O-ECNFs, contact time, pH, initial concentration, and temperature on adsorption process were explored. The adsorption isotherm and kinetic were studied by numerous non-linear models. The obtained results confirmed that the incorporation of O-ECNFs into the hydrogel network decreased the swelling capacity and improved its ability towards MB dye removal. The adsorption process depended on the pH value of the dye solution. Additionally, the adsorption and kinetic results were fitted using the Freundlich isotherm model and pseudo second order model (PSO), respectively. Moreover, the new adsorbents can be recycled for at least five cycles keeping its adsorption capacity and can be easily recovered without loss in its initial weight. [ABSTRACT FROM AUTHOR]

Activated electrospun carbon nanofibers (A-ECNFs) with micro/mesoporous structures and high surface areas (1615 m2 g−1) were prepared using electrospinning technique followed by carbonization and alkali activation. The adsorption of Congo red (CR) and methylene blue (MB) dyes by A-ECNFs from aqueous solutions was investigated and compared with those of pristine ECNFs. The textural characteristics and morphology of the prepared pristine and activated ECNFs were characterized using various techniques. The adsorption performance was found to be associated to the surface area, porosity, and surface charges of the prepared adsorbents, the nature and molecular size of the dyes, and the pH and temperature of the solution. Six nonlinear isotherm models were applied to analyze the adsorption equilibrium data, and the results showed that the adsorption behavior could be appropriately described using the Redlich–Peterson isotherm model. The kinetic results for the adsorption of CR and MB onto A-ECNFs were fitted reasonably well to the Elovich model and were fitted by a pseudo-second order (PSO) model onto the pristine ECNFs. According to the thermodynamic results, the adsorption of CR and MB onto the A-ECNFs was endothermic and spontaneous. In addition, the reusability of the A-ECNFs was evaluated over five adsorption-desorption cycles. [ABSTRACT FROM AUTHOR]

In this study, an electrospinning method was used to produce highly conductive freestanding carbon nanofibers (CNFs). The freestanding CNFs are compatible with hierarchical growth techniques, such as hydrothermal processes, for the nanostructure engineering of supercapacitor electrodes with enhanced electrochemically active sites. Therefore, the flower-like FeMoO 4 @CNF nanosheets were investigated to improve the electrochemical performance using aqueous and neutral electrolytes (Na 2 SO 4 and K 2 SO 4). The optimized FeMoO 4 @CNF electrode exhibits areal capacitances of 252 and 220 mF·cm−2 at a high current density of 2.5 mA·cm−2 with Na 2 SO 4 and K 2 SO 4 electrolytes, respectively. The wide potential window (1.6 V) of the symmetric supercapacitor delivered maximum energy densities of 22.4 and 19.6 μWh·cm−2 at a power density of 2 mW·cm−2 for Na 2 SO 4 and K 2 SO 4 electrolytes, respectively. [ABSTRACT FROM AUTHOR]

The wearable electronics market is growing exponentially and has benefited considerably from a versatile electrospinning technique capable of fabricating freestanding, binder-free fibers. Using this method in the current study, electrospun fibers were produced from a polymer-salt-ZIF-DMF solution. The obtained fibers were annealed to prepare Fe-ZnO/carbon nanofibers (CNFs), which exhibited a wide potential window of 0–1.6 V in an aqueous electrolyte (6 M KOH). Moreover, the composite fibers exhibited a large interfacial area between the electrode and electrolyte and reduced the ion transport distance during operation. Consequently, a high capacitance of 499 mF·cm–2 was attained at a current density of 5 mA·cm–2. Notably, high energy densities of 0.23–0.18 mWh·cm–2 were achieved owing to the excellent synergy between ZIF-7-derived ZnO and Fe-activated CNFs. The energy density of Fe-ZnO/CNF was approximately four times higher than that of ZnO/CNF at a power density of 16 mW·cm–2. Electrochemical stability testing through 10,000 galvanostatic charging–discharging cycles revealed a capacitance retention of ∼95 %. Practical applications and bendability tests of environmentally benign flexible supercapacitors underscored the potential of the freestanding electrodes in fabricating wearable, portable electronic devices. • Fe-ZnO/carbon nanofibers (CNFs) were fabricated using the polymer-salt-ZIF-DMF. • A high capacitance of 500 mF·cm–2 was attained at a current density of 5 mA·cm–2. • The energy density for Fe-ZnO/CNF was 4 times higher than those of ZnO/CNF without iron. • Electrochemical stability was tested via the galvanostatic charging–discharging cycles of 10,000. [ABSTRACT FROM AUTHOR]

[Display omitted] • PVP/ZIF-7/PAN nanofibers carbonized at 900 °C yielded flexible ZnO P /C. • A capacitance of 382.5 mF cm−2 was obtained at a current density of 1 mA cm−2. • ZnO P /C demonstrated a capacitance retention of ∼ 101 % over 10,000 cycles. • ZnO P /C delivered an energy density of 49 μWh cm−2 at a power density of 2 mW cm−2. This study investigates the carbonization of electrospun fibers derived from zeolitic imidazolate framework (ZIF)-7/polyacrylonitrile solutions containing urea or polyvinylpyrrolidone (PVP). The carbonization yields highly flexible composites comprising nitrogen-doped carbon nanofibers and ZnO. Notably, using PVP as a nitrogen source generates a composite exhibiting excellent electrochemical performance. Specifically, it delivers a high capacitance of 382.5 mF cm−2 at a current density of 1 mA cm−2. Furthermore, this composite demonstrates capacitance retentions of approximately 101 % and 80 % after 10,000 cycles and a 90° bending test, respectively. The charge-storage capability of the PVP-based ZnO P /C composite surpasses that obtained without PVP by 1.4 times. Additionally, a composite fiber mat of ZnO P /C obtained via one-step electrospinning exhibits exceptional electrical conductivity and an energy density of 49 μWh cm−2 at a power density of 2 mW cm−2. These findings highlight the potential of this material as an electrode for supercapacitors. [ABSTRACT FROM AUTHOR]

Chlorinated polyethylene (CPE) filled with functionalized heat treated carbon nanofiber (CNF) nanocomposites were prepared using two different techniques like melt mixing and solution cum melt mixing. A better dispersion of CNFs in nanocomposite was achieved by solution cum melt mixing compared to only melt mixing process. The effect of mechanical, electrical conductivity ( σ) , and electromagnetic interference shielding effectiveness (EMI SE) were studied. Nanocomposites prepared by solution cum melt mixing process showed higher mechanical properties, electrical conductivity ( σ ), and electromagnetic interference shielding effectiveness (EMI SE) compared to that of melt mixing process. 1 wt% CNFs filled nanocomposites prepared by the solution followed by melt mixing showed 124% higher tensile strength whereas at the same percentage of CNFs, melt processed nanocomposite exhibited 58% higher in tensile strength compared to neat CPE. The EMI SE and σ of both types of nanocomposites were increased with increasing CNFs loading. At 10 wt% CNFs loading, solution cum melt processed nanocomposite showed EMI SE 24 dB; whereas at the same wt% of CNFs loading, melt processed nanocomposite showed 22 dB. Thermogravimetric analysis was carried to investigate the thermal stability of CPE/CNF nanocomposites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn-doped PAN nanofibers were decorated with ZIF-67. • Oriented attachment of PVP/ZIF-67 occurred on Mn-doped PAN-2MI nanofibers. • PVP/ZIF-67/Mn-fibers carbonized at 900 ℃ resulted in flexible C/Co-CoO x /Mn-CNF. • The areal capacitance of 1263 mF·cm−2 was obtained at a current density of 0.25 mA·cm−2. • The energy density of 0.18 mWh·cm−2 was obtained at a power density of 0.5 mW·cm−2. Electrodes for flexible supercapacitors were fabricated from manganese-doped carbon nanofibers (Mn-CNF) decorated with carbon-coated Co-CoO x (C/Co-CoO x) nanotubes. The Mn-doped polyacrylonitrile (PAN)–2-methylimidazole (2MI) solution was electrospun using optimized Mn concentrations and ZIF-67 was then surface loaded by wet impregnation with added polyvinylpyrrolidone (PVP). These ZIF-67 loaded Mn-fibers, when annealed, resulted in carbon-coated C/Co-CoO x nanotubes on the Mn-CNF surface. In the presence of PVP, ZIF-67 oriented attachment occurs, forming evenly dispersed CoO x particles even after high temperature annealing. XRD spectra exhibit the formation of metallic Co nanoparticles (NPs), whereas Raman spectra and XPS indicate Co particle oxidation. A carbon coating limits the oxidation of Co; thus, the particles are called C/Co-CoO x. A symmetric supercapacitor cell prepared using the CNFs decorated with C/Co-CoO x using an aqueous electrolyte has a capacitance of 1263 mF⋅cm−2 at a current density of 0.25 mA⋅cm−2 and a wide potential window of 1.4 V for the optimal case. Long-term cycling showed 110 % capacitance retention after 10,000 cycles. Moreover, bending tests and powering LEDs demonstrated the flexibility and improved charge storage of the prepared nanofiber electrodes. [ABSTRACT FROM AUTHOR]