Search

Aerogels are highly porous structures produced by replacing the liquid solvent of a gel with air without causing the collapse of the solid network.

Constructing consecutive proton-conducting nanochannels and optimizing nanophase-separation within proton exchange membrane (PEM) was of guiding significance for improving proton transfer. Metal organic framework (MOF), as a novel and functional material had drawn increasing attention in the research of proton PEM because of its flexible tunability and designability. Herein, a novel MOF-based nanofibrous mats (NFMs) were prepared by the self-assembly of zeolitic imidazole framework-67 (ZIF-67) onto polyacrylonitrile (PAN) NFMs. Subsequently, the ZIF-67 NFMs were incorporated into Nafion matrix to prepare ZIF-67@Nafion composite membrane which aimed at constructing consecutive proton-conducting channels. Especially, the acid–base pairs between N–H (ZIF-67 NFMs) and –SO3H (Nafion) could promote the protonation/deprotonation and subsequent proton leaping via Grotthuss mechanisms. As expected, the ZIF-67@Nafion-5 composite membrane showed a promising proton conductivity of 288 mS/cm at 80 °C and 100% RH, low methanol permeability of 7.98 × 10−7 cm2s−1, and superior power density of 298.68 mW/cm2 at 80 °C and 100% RH. In addition, the resulting composite membrane exhibited considerable enhancement in thermal stability and dimensional stability. This promising strategy provided a valuable reference for designing high-performance PEMs.

Fabricating a high-performance adsorbent as a desirable candidate for removing Pb2+ from aqueous water remains a challenge. Aramid nanofibers (ANFs) are promising building blocks that have realized multifunctional applications due to their intrinsic mechanical and chemical stability. Herein, an in situ loading strategy for preparing nanofiber composite aerogel was proposed by assembling ANFs into a 3D aerogel and applying it as host media for the in situ polymerization of pyrrole followed by facile redox reaction between the polypyrrole (PPy) and MnO4–1 to load manganese dioxide (MnO2). The idea was to fully exploit the structural advantages of ultra-low bulk density, large specific surface area, and high porosity of ANFs, and the possible chemical adsorption characteristics of MnO2 on the basis of ion exchange reaction. The adsorption capacity of 3D ANF/MnO2 composite aerogel was as large as 554.36 mg/g for Pb2+. The adsorption mechanism based on an exchange reaction between Pb2+ and protons on the surface of MnO2 was also investigated. The desorption results showed that the adsorption performance could remain up to 90% after five times of usage. In conclusion, this research provides promising insights into the preparation of high-performance lead adsorbent for water treatment.

Metal–organic frameworks (MOFs) exhibit high proton conductivity, thermal stability, and offer immense flexibility in terms of tailoring their size. Owing to their unique characteristics, they are desirable candidates for proton conductors. Nevertheless, constructing ordered MOF proton channels in proton exchange membranes (PEMs) remains a formidable challenge. Herein, blend nanofibers of cellulose and UiO-66-NH2 (Cell–UiO-66-NH2) obtained via the electrospinning process were embedded in a sulfonated polysulfone matrix to obtain high-performance composite PEMs with an orderly arrangement of UiO-66-NH2. Comprehensive characterization and membrane performance tests reveal that composite membrane with 5 wt% (nominal) UiO-66-NH2 have revealed high proton conductivity of 0.196 S cm−1 at 80 °C and 100% relative humidity. Meantime, the composite membrane exhibits a low methanol permeability coefficient (~5.5 × 10−7 cm2 s−1). Moreover, the composite membrane exhibits a low swelling ratio (17.3%) even at 80 °C. The Cell–UiO-66-NH2 nanofibers exhibit strong potential for use as a proton-conducting nanofiller in fuel-cell PEMs.

Air pollution and public health incidents have become a serious global concern. Hierarchical nanofibrous membranes are considered as high-performance filters with an advanced structure, but their reliable fabrication is still challenging. Herein, a novel methodology involving the combination of a multi-orifices solution blowing technique process and low molecule organogel self-assembly strategy is reported to construct a hierarchical dual-nanonet of polymer nanofibers and supramolecular nanofibrils. Through an adsorption–nucleation–growth model, ultrathin supramolecular nanofibrils (10–30 nm) were assembled in situ within a fluffy solution-blown nanofiber mat with strong inter-fiber connections. Benefiting from the synergistic effects of the ultrathin diameter, small pore size, high porosity and stable inter-fiber connections, the hierarchical dual-nanonet demonstrates robust mechanical strength, a high filtration efficiency (99.999% for 0.3 μm), low pressure drop (32 Pa), a high quality factor (0.189 Pa−1), and a boosted moisture permeation. The comprehensive performances indicate promising applications in various filtration applications, especially in the field of personal protective equipment.

Proton-conducting nanofiber hybrid membranes (PC-NFHMs) as promising candidates, are widely used for proton exchange membrane fuel cells (PEMFCs), combining the properties and some synergism from interactions between nanofibers and the polymer matrix. The PC-NFHMs possess superior characteristics compared to individual ion-conducting polymeric membranes or free-standing electrolyte inorganic films. Herein, this critical review presents the progress of PC-NFHMs, with specific focus on the combinations of multifunctional nanofibers and emerging proton transfer carriers, such as metal organic frameworks (MOFs), porous organic cages (POCs), polyhedral oligomeric silsesquioxanes (POSSs), amino acids (AAs), etc. The unique properties and performance of the different types of multifunctional nanofibers and their derivatives are described with respect to their use as PC-NFHMs. Besides, relevant characterization studies including small angle X-ray scattering (SAXS), nuclear magnetic resonance (1H-NMR), and molecular dynamics calculation (MDC), have been briefly summarized to understand proton-conducting mechanisms (Vehicle and Grotthuss mechanisms) in electrolyte membranes. These systematic discussions and proposed directions can trigger thoughts and provide ways to reasonably design PC-NFHMs for PEMFCs in the near future.

Proton conduction is a ubiquitous fundamental phenomenon in biological systems. Biology has solved the problem of energy-related proton conduction, in which the exposed amino acids in the protein ordered channels play a key role in proton conduction. In this contribution, amino acids (glutamate, lysine, and threonine) were attached to metal organic framework (MOF) nanoparticles, which were incorporated into sulfonated polysulfone matrix forming bio-proton channels for the nanocomposite membranes. It is shown in the results that the amino acid-functionalized MOF can help to enhance the proton conductivity and the proton exchange membrane with glutamate-functionalized MOF demonstrate excellent proton conductivity of 0.212 S cm−1 at 80 °C and 100% relative humidity. Meanwhile, the methanol permeability coefficient of the nanocomposite membrane is reduced to 5.8 × 10−7 cm2 s−1. The nanocomposite membranes demonstrate excellent proton conductivity, dimensional stabilities, water absorption, and resistance to methanol performance. Therefore, this material is promising for fuel cells.

Based on the construction strategy of proton transport channels, we design a high-performance proton exchange membrane (PEM) with ordered deoxyribonucleic acid (DNA)-functionalized graphene oxide (GO) and Nafion matrix via the electrostatic layer-by-layer deposition (ELD) technique, which is a novel method of membrane formation aided by electrostatic force. The effects of different content rations of single-strand DNA (ss-DNA) molecules and GO (ss-DNA@GO) on the proton conductivity, methanol permeability, and single cell performance of composite PEMs are investigated. The composite membrane shows a high proton conductivity of 351.8 mS cm−1 (80 °C, 100%RH) but a low methanol permeability of 1.63 × 10−7 cm2 s−1 at room temperature. Furthermore, the composite membranes are assembled into direct methanol fuel cells at 60 °C, and Nafion/DNA@GO-2/5 exhibits a maximum power density of 255.33 mW cm−2, which is 2.42 times higher than that of pure Nafion. This work explores the application potential of DNA@GO in PEM and provides a bioinspired avenue to designing next-generation high-performance PEM for fuel cells.

Nanofiber mats have received considerable attention from researchers in the field of particulate protection. In this study, polyvinylidene fluoride (PVDF) nanofiber mats were prepared on a large scale by a solution blowing process, and then crosslinked by ultraviolet (UV)-radiation using trimethylolpropane tri-acrylate (TMPTA) as a crosslinker. The structure, morphology, mechanical and thermal properties, and protective performance of the nanofiber mats were evaluated. Results show that the addition of TMPTA and UV treatment decreased the diameter of the nanofibers and enhanced the mechanical properties, air permeability, and moisture permeability. Nanofiber mats show higher filtration and lower filtration resistance compared with a commercial product. Furthermore, the nanofiber mats were bonded with Nylon 6 fabric, which showed good performance as a novel functional layer in protective clothing.

Solar-driven interfacial evaporation is an emerging technology to obtain fresh water using solar energy. However, the complicated system and the corresponding fabrication process severely restrict its large-scale and cost-effective production. Herein, an all-in-one solar-driven interfacial evaporator was fabricated via a hybrid nanofibrous aerogel of aramid nanofibers (ANFs), carbon nanotubes (CNTs), and gold nanoparticles (AuNPs). Assisted by the reprotonation of the ANFs, CNTs are assembled into the nanofibrous network for through-body light-to-heat activity, and AuNPs are set on the surface layer to enhance solar absorption. The aerogel also features low thermal conductivity to suppress heat losses and high capillary action to wick and confine water within the aerogels. Benefitting from the synergistic effect, the aerogel shows a high evaporation rate of 1.53 kg m

High-performance thermal insulators are urgently desired for energy-saving and thermal protection applications. However, the creation of such materials with synchronously ultralow thermal conductivity, lightweight, and mechanically robust properties still faces enormous challenges. Herein, a proton donor-regulated assembly strategy is presented to construct asymmetric aramid nanofiber (ANF) aerogel membranes with a dense skin layer and a high-porous nanofibrous body part. The asymmetric structure originates from the otherness of the structural restoration of deprotonated ANFs and the resulting ANF assembly due to the diversity of available proton concentrations. Befitting from the synergistic effect of the distinct architectures, the resulting aerogel membranes exhibit excellent overall performance in terms of a low thermal conductivity of 0.031 W·m

Developing an efficient and sustainable approach for removing dyes from wastewater remains a challenge. Herein, we report a facile and reliable strategy to create ZnS nanoparticles (NPs) supported by cellulose/chitosan sponge (ZnCCSs) via hydrothermal decomposition of xanthates and in situ synthesis of ZnS NPs. ZnCCSs demonstrate high porosity, low bulk density, outstanding compressibility, and uniformly immobilized ZnS NPs. Benefiting from the affinity sites of polysaccharide sponge skeleton and highly exposed ZnS NPs, ZnCCSs show an excellent synergistic effect of adsorption and photocatalytic degradation performances in removing Congo red pollutants. By regulating the structure through the ratio of components, ZnCCSs show a high removal ratio of 96.53% and excellent stability after reusability cycles. The adsorption and degradation behavior and the photodegradation mechanism are also investigated through trapping experiments. This study provides a promising way of removing dye contaminants through a combination of various mechanisms.

Proton transfer using amino acids as proton delivery sites is a ubiquitous and important process in organisms. In this study, novel proton-conducting nanofibers were prepared on the basis of a bionic design concept from two perspectives, namely, proton transfer site and proton transfer route, by immobilizing four kinds of amino acids, namely, serine, arginine, lysine, and glycine, onto chitosan (CS) nanofibers. Nanocomposite membranes were then fabricated by filling the pores of the amino acid-functionalized CS nanofiber mats (AA-CSNFs) with sulfonated polysulfone (SPSF). The methanol crossover of the nanocomposite membranes with AA-CSNFs was reduced and their proton conductivity was increased compared with those of pure SPSF membrane. The nanocomposite membrane embedded with the serine-functionalized CS nanofibers exhibited an excellent proton-conducting ability with the highest proton conductivity of 0.192 S/cm at 80 °C. Results indicated that these nanocomposite membranes showed potential for applications in proton exchange membrane fuel cells with superior combined properties.

A nanofibrous microfiltration membrane with high flux, low pressure drop, and high retention capacity was fabricated by pore filling of copolyetherester nanofibers (low-melting-point polyester; melting point of 110℃) into a poly(ethylene terephthalate) nonwoven scaffold. Short low-melting-point polyester nanofibers were anchored on the surface of the poly(ethylene terephthalate) fibers by heat treatment to form a crosslinked nanostructured mesh with very high porosity and high specific surface area. The pore size and distribution of the membranes can be adjusted by varying the loading amount of nanofibers. The resulting membrane not only possessed good interception ability for 5, 3, and 1.3 µm polystyrene microspheres but also exhibited desirable water permeability. In the circulating filtration test, with the accumulation of membrane fouling in the filtration, the membrane was also effective in retaining particulate matter while improving the antipollution ability. These properties are desirable for the effective removal of pollutants on the membrane and restoration of the membrane flux.

Proton exchange membranes with short-pathway through-plane orientated proton conductivity are highly desirable for use in proton exchange membrane fuel cells. Magnetic field is utilized to create oriented structure in proton exchange membranes. Previously, this has only been carried out by proton nonconductive metal oxide-based fillers. Here, under a strong magnetic field, a proton-conducting paramagnetic complex based on ferrocyanide-coordinated polymer and phosphotungstic acid is used to prepare composite membranes with highly conductive through-plane-aligned proton channels. Gratifyingly, this strategy simultaneously overcomes the high water-solubility of phosphotungstic acid in composite membranes, thereby preventing its leaching and the subsequent loss of membrane conductivity. The ferrocyanide groups in the coordinated polymer, via redox cycle, can continuously consume free radicals, thus helping to improve the long-term in situ membrane durability. The composite membranes exhibit outstanding proton conductivity, fuel cell performance and durability, compared with other types of hydrocarbon membranes and industry standard Nafion® 212., Proton exchange membranes with short-pathway through-plane proton conductivity are attractive for proton exchange membrane fuel cells. Here the authors align proton conducting channels orthogonal to the plane of composite proton exchange membranes using a magnetic field for improved fuel cell performance.

Fabricating a high-performance adsorbent as a desirable candidate for removing Pb

There are several methods of preparing nanofiber yarns, but little work has been reported using a combination of electrospinning and solution blowing methods (i.e., electrostatic-solution blow spinning) to prepare nanofiber yarns. In this study, a response surface method (RSM) based on Box–Behnken design was used to investigate the relationship between the yarn parameters and yarn diameter, and the process was optimized. The yarn diameter was simulated by electrostatic voltage, air pressure, winding speed and funnel velocity. The correlation coefficients before and after adjustment were 0.97 and 0.95, respectively, through variance analysis, which verified the accuracy of the yarn diameter model. The results showed that the influence of each experimental factor on the yarn diameter was in descending order of winding speed, electrostatic voltage, airflow and funnel velocity, and there were interactions among the factors. The BDD response model was used to obtain the best experimental conditions, which provided a good theoretical reference for the preparation of polyacrylonitrile nanofibers. In addition, the effects of voltage and air pressure on the diameter of the nanofiber and yarn and the effects of the twist coefficient on the shape and mechanical properties of the yarn were studied. The results showed that with the increase of voltage and air pressure, the diameter of the nanofiber decreased, and the yarn diameter decreased first and then increased. When the twist factor was 100, the twist angle of the yarn was 49.91°, the breaking strength was 12.92 MPa and the elongation at break was 81.34%.

Optimization of chemical composition and topography is vital to obtain high-performance proton exchange membranes (PEMs). In this work, cellulose nanofibers were incorporated with phosphoric acid and embedded into the sulfonated poly (ether sulfone) (SPES) matrix to develop PEMs with improved proton conductivity by building proton transfer channels and providing additional proton transport sites. The morphology and chemical structure of the nanofibers doped with different phosphoric acid concentrations and the performance of the composite PEMs were characterized by multi-technics. The results showed that the thermal stability, water swelling ratio (SR) and proton conductivity of the composite membrane were improved in the phosphoric acid-doped cellulose nanofibers. The maximum conductivity (0.154 S/cm, 80 °C, 100 RH) was reached for composite membranes with cellulose nanofibers doped with 0.25 mol/L phosphoric acid. Hence, composite membranes containing proton-conducting cellulose nanofibers could be used to develop novel PEMs for fuel cells.

Lithium-sulfur battery is regarded as one of the promising next-generation energy storage to electrical and portable devices thanks to its extremely high theoretical capacity, energy density, good environmental protection and low cost. However, the practical application of lithium-sulfur battery is still greatly impeded by the low Coulombic efficiency and the short lifespan, which is mainly attributed to the polysulfide shuttle and the uncontrollable lithium dendrite growth. Suppressing the growth of the lithium dendrite and hindering the notorious reaction between soluble polysulfides and lithium are extremely critical not only to a safe and efficient lithium anode, but also to the high-capacity lithium-sulfur battery. A comprehensive review of various strategies for strengthening the anode stability of lithium-sulfur battery is presented in this paper, including modifying the electrolyte and current collector, employing artificial protection films and finding alternative anodes to replace the lithium anode. The effects of different selections and the resulting properties of the anodes on the overall lithium-sulfur battery performance are discussed. The current research challenges and future perspectives associated with lithium-sulfur battery anode are also discussed.

A novel approach is proposed to prepare a proton-conductive nanochannel membrane based on polyvinylidene difluoride (PVDF) porous membrane with modified SiO2 nanospheres. The hydrophilic PVDF porous membrane with a 450-nm inner pore size was chosen as the supporting structure. Pristine SiO2 with a uniform particle size of 95–110 nm was synthesized and functionalized with –NH2 and –COOH, respectively. Through-plane channels of porous membrane and arranged functional nanoparticles in pores could contribute to constituting efficient proton transfer channels. The characteristics such as morphology, thermal stability, water uptake, dimensional swelling, proton conductivity and methanol permeability as proton exchange membranes, of the SiO2 nanospheres, and the composite membrane were investigated. The formation of ionic channels in membrane enhanced the water uptakes and proton conduction abilities of the composite membranes. PVDF/Nafion/SiO2–NH2 exhibited superior proton conductivities (0.21 S cm−1) over other samples due to several proton sites and the acid–base pairs formed between –NH2 and –SO3H. Furthermore, all the composite membranes exhibited improved methanol resistance compared with Nafion. Therefore, such a design based on porous membrane provided feasibility for high-performance proton exchange membrane in fuel cell applications.

In this work, an affinity nanofiber membrane was successfully prepared by solution blowing of arginine-modified chitosan (CS-Arg) for bovine serum albumin (BSA) adsorption. CS-Arg was firstly synthesized by coupling L-arginine onto chitosan backbone. Then, CS-Arg nanofiber membranes (CANFs) were fabricated using solution blowing process with Polylactide (PLA) as assistant polymer. The results showed that CANFs effectively adsorbed BSA, and the adsorption capacities were influenced by the degrees of substitution (DS) of arginine in CS, pH value, contact time, and initial protein concentration. The highest adsorption capacity of 445.19 mg/g was achieved uvnder the following conditions: DS of 43.7 %, pH of 7.14, and initial concentration of 3.0 mg/ml. BSA adsorbed on the CANFs membrane conformed to Langmuir model, and the adsorption rate was consistent with the second-order kinetics model. This work implies that an arginine-modified chitosan nanofiber-based novel biomaterial has a potential application in adsorption of BSA.

A new type of hydrophobic polyacrylonitrile (PAN) nanofiber is fabricated by solution blowing of a blend solution of fluorine-containing polyacrylate (FPA) and PAN. The nanofibers’ surface composition, hydrophobicity, and protection ability were evaluated to clarify the effects of FPA addition. Results revealed that FPA addition increased the nanofiber diameter, as well as enhanced the hydrophobicity and transport properties of the nanofiber mats. The mats had average water contact angles of 123.44°, 132.11°, and 137.11° for FPA contents of 0.66 wt%, 1.98 wt%, and 3.30 wt%, respectively. All these results suggested the potential of the solution blowing nanofiber mats as protection materials.

Cellulose nanofibers were embedded into sulfonated poly (ether sulfone) matrix to heighten the water retention and proton conductivity of proton exchange membranes (PEMs). Cellulose nanofibers were obtained by hydrolyzing cellulose acetate nanofibers, which were prepared via electrostatic-induction-assisted solution blow spinning. Morphology, thermal stability, and mechanical properties of the PEMs were investigated. The results showed that proton conductivity, water uptake, and methanol permeability of the composite membranes were improved. Hydrophilicity of the composite membranes was gradually improved with the addition of nanofibers. When the content of nanofibers was 5 wt%, the highest proton conductivity was 0.13 S/cm (80 °C, 100% RH). Therefore, the cellulose nanofiber could be used as support materials to enhance the performance of proton exchange membranes, the composite membranes have potential application in Direct methanol fuel cells (DMFCs).

N-Alkylated chitosan (NACS) may improve the blood clotting efficiency of chitosan (CS). To study its blood coagulation capability, a series of NACSs with various carbon chain lengths and degrees of substitution (DS) of alkyl groups were synthesized and characterized by FTIR, NMR, elemental analysis, and X-ray diffraction (XRD). The corresponding NACS nanofiber membranes (NACS-NM) were subsequently fabricated by electronic spinning technique. SEM, XRD, DSC, surface area, porosity, contact angle, blood absorption, and mechanical properties were used to characterize the CS-NM/NACS-NM. Moreover, cytotoxicity, coagulation, activated partial thromboplastin time, plasma prothrombin time, thrombin time, and platelet aggregation tests were performed to evaluate the biocompatibility and blood coagulation properties of NACS-NM. The results showed that NACS-NM was not cytotoxic. NACS-NM with DS of 19.25% for N-hexane CS (CS6b), 17.87% for N-dodecane CS (CS12b), and 8.97% for N-octadecane CS (CS18a) exhibited good blood clotting performance. Moreover, NACS-NMs favored the activation of coagulation factors and platelets. In addition, intracellular Ca

A novel hierarchical nanofibrous membrane was demonstrated via in situ self-assembly of 1,3:2,4-dibenzylidene-d-sorbitol (DBS) supramolecular fibrils in solution-blown polyacrylonitrile (PAN) nanofibers. The formed DBS fibrils were interconnected into networks and anchored onto the PAN nanofibers, which decreased the pore sizes and enhanced the mechanical properties, the filtration efficiency, and particularly the flux.

Textile-based electronics characterizing easy integration into textile garments and good wearability have received considerable attentions. However, it is still a huge challenge to integrate multiple functions into single electronic device, especially for those having different even opposite requirements in electrical properties. In this work, an anisotropic electrically conductive composite was prepared by encapsulating conductive knitted fabric (CKF) into polyurethane (PU). Based on anisotropic electrical conductivity, i.e., extremely low and stable resistivity in the coursewise direction and significant variation of resistivity in the walewise direction during tensile strains, the composite could efficiently integrate the electro-heating and strain-sensing functions that required opposite electrical properties. When applied for electro-heating applications in the coursewise direction, the CKF/PU composite exhibited fast thermal response, ultrahigh electric-thermal conversion (140 °C at 4 V), and stable electrothermal performance under a large strain (40%) or after long-term use (>1000 stretching cycles). When applied for strain-sensing applications in the walewise direction, the composite showed good sensing performances, including high sensitivity (GF of −8.1 at a 5% strain), low hysteresis, good reproducibility and stability (>1000 cycles), which enabled the device as a wearable sensor to accurately detect human joint movements and subtle motions. Furthermore, the self-healing function was exploited for the CKF/PU electronic device, by which the abnormal sensing property could be fully repaired at human body temperature. This work may shed new light on the future development of high-performance multifunctional wearable electronics with the anisotropic conducting feature.

The fabrication of a high-efficiency adsorbent, as a promising candidate for removing metal ions and organic dyes from aqueous solution, is a research hotspot but remains challenging. Aramid nanofibers (ANFs) are emerging building blocks that have realized multifunctional applications in various fields because of their intrinsic mechanical and chemical stability. In this research, three-dimensional (3D) ANF aerogel was assembled and applied in for in situ assembly of zeolitic imidazole framework-67 (ZIF-67). The aim, was to fully exploit the structural advantages of this composite’s ultra-low bulk density, large specific surface area, and high porosity, as well as provide more available adsorption sites by ZIF-67 polyhedrons, to facilitate pollutant adsorption from waste water. The prepared 3D ANF/ZIF-67 composite aerogel possessed favorable adsorption performance for heavy metal ions (250.95 and 183.29 mg/g for Cu2+ and Cr6+, respectively) and organic dyes (199.36 and 65.98 mg/g for CV and MO, respectively), greatly exceeding that of the corresponding 3D ANF aerogel. Desorption experiments further demonstrated that up to 80% adsorption performance for heavy metal ions and organic dyes could be maintained after five times of usage. Hence, this research can provide new insights into the preparation of highly efficient adsorbents for water treatment.