Polyvinylidenefluoride-co-hexafluoropropylene Research Articles

Dual fillers ZrO2/BaTiO3 incorporated PVDF-HFP nanofiber composite for enhanced piezoelectric energy harvesting and piezo catalytic reduction of hexavalent chromium

A novel Piezoelectric Nanogenerator (PENG) was designed and fabricated using electrospun nanocomposite fibers of Poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) with Barium Titanate (BaTiO3) and Zirconium Oxide (ZrO2) as dual fillers. ZrO2 fillers were incorporated at varying loadings into the PVDF-HFP polymer matrix to produce the PBZ nanocomposite fibers. The synergistic effect of BaTiO3 and ZrO2 significantly enhanced the piezoelectric performance of the resulting PBZ composite. The dual fillers also induced the nucleation of the β-phase in the nanofiber composite, which further improved its piezoelectric properties. This enhancement rendered the composite highly effective for dual applications: energy harvesting and the piezocatalytic reduction of hexavalent chromium (Cr(VI)). The PENG exhibited an open-circuit voltage of 6.3 V, a current of 0.67 µA, and a power density of 30.91 mW/m². The device was also tested in real-world scenarios, such as finger tapping and shoe sole applications, additionally it successfully powered up to five LEDs and charged a 1–2.2 μF capacitor to approximately 1–3 V under an external load of 1 N at 2 Hz. In addition to energy harvesting, the PBZ nanofibers demonstrated remarkable piezocatalytic activity by converting highly toxic Cr(VI) to Cr(III), which is biologically essential in trace amounts. The PBZ nanofiber mats achieved an impressive Cr(VI) reduction rate of up to 90.1 % under acidic conditions within 20 minutes and were recyclable for up to five cycles without loss of efficiency. Furthermore, Density Functional Theory (DFT) calculations, focusing on the Density of States (DOS), were performed to elucidate the underlying mechanisms contributing to the observed improvements in piezoelectric and piezocatalytic performance.

Radiative cooling materials prepared by SiO2 aerogel microspheres@PVDF-HFP nanofilm for building cooling and thermal insulation

Radiative cooling is promising in meeting the current global demand for green sustainable development. However, the effective cooling of the existing radiant cooler will be limited due to the serious solar energy absorption and poor thermal insulation performance on the cold side. To addresss these issues, we propose herein a novel composite material of silicon dioxide (SiO2) aerogel microspheres combined with polyvinylidene fluoride-cohexafluoropropylene (PVDF-HFP) nanofiber membrane, in which SiO2 aerogel microspheres are firstly synthesized by sol-gel method and then incorporated into PVDF-HFP nanofiber membrane to give radiative cooling performance. As we expected, the molecular vibration characteristics of PVDF-HFP nanofiber membrane and the phonon polarization resonance of Si-O-Si bond in the transparent window can enhance the infrared emissivity of the membrane surface. In addition, the high porosity and the mesoporous structure formed by the interconnection of nano-network skeletons of SiO2 aerogel microspheres determine its excellent thermal insulation performance. The as-prepared material displays that the average solar reflectance of the composite membrane is 96.07 % and the average infrared emissivity of the atmospheric window is 94.95 %. Notably, when the average solar radiation intensity is 885.56 W•m−2, the passive radiative cooling temperature during the day can reach 11.2 °C. Furthermore, this material has excellent self-cleaning and thermal insulation performance, making it a potential radiant cooling candidate in many fields.

Omniphobic PTFE based Hollow Fiber Membrane with ZnO Nanoparticles Deposition via Universal Spray Technique

This investigation aimed to enhance the hydrophobicity of a polytetrafluoroethylene (PTFE) hollow fiber membrane, transforming it into an omniphobic surface. This was achieved by coating the membrane with a mixture of zinc oxide nanoparticles (ZnO-NPs) and polyvinylidene fluoride-cohexafluoropropylene (PVDF-HFP) using the universal spray technique. The membrane's morphology and performance were evaluated based on the number of spray cycles, which influenced the coating thickness on the membrane surface. The spraying process was varied up to 4 cycles to determine the membrane with the most effective deposition of ZnO NPs in terms of water contact angle and liquid entry pressure (LEPw). Results indicated that the membrane spray-coated up to 4 cycles, denoted as PTFE-4, exhibited a rough hierarchical re-entrant morphology, imparting omniphobic characteristics. The optimized membrane demonstrated a high water contact angle of 170° and a liquid entry pressure of 2.6 bar. Fourier-transform infrared (FTIR) and energy dispersive analysis of X-rays (EDX) confirmed the successful chemical integration of ZnO NPs onto the commercial membrane. This research holds significance for the future of membrane distillation in treating wastewater containing low surface tension pollutants.

Robust Solid-State Na-CO2 Battery with Na2.7Zr2Si2PO11.7F0.3-PVDF-HFP Composite Solid Electrolyte and Na15Sn4/Na Anode.

Solid-state Na-CO2 batteries are a kind of energy storage devices that can immobilize and convert CO2. They have the advantages of both solid-state batteries and metal-air batteries. High-performance solid electrolyte and electrode materials are important for improving the performance of solid-state Na-CO2 batteries. In this work, we investigate the influence of fluorine doping on the structure and ionic conductivity of Na3Zr2Si2PO12 (NZSP). An ionic conductive solid electrolyte membrane was prepared by compositing the inorganic solid electrolyte Na2.7Zr2Si2PO11.7F0.3 (NZSPF3) with poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP). It shows an ionic conductivity of up to 2.17 × 10-4 S cm-1 at room temperature, a high sodium ionic transfer number of ∼0.70, a broad electrochemical window of ∼5.18 V, and better mechanical strength. Furthermore, we studied the Na15Sn4/Na composite foil with the ability to inhibit dendrite as the anode for solid-state Na-CO2 batteries. Through density functional theory (DFT) calculations, the Na15Sn4 particle has been verified with a strong sodiophilic property, which reduces the nucleation barrier during the deposition process, leading to a lower overpotential. The symmetric cell assembled with the composite solid-state electrolyte NZSPF3-PVDF-HFP and Na15Sn4/Na composite anode can inhibit the growth of Na dendrites effectively and maintain the stability of the whole cell structure. Solid-state Na-CO2 batteries assembled with Ru-carbon nanotube (Ru-CNTs) as cathode catalysts exhibit a high discharge capacity of 6371.8 mAh g-1 at 200 mA g-1, excellent cycling stability for 1100 h, and good rate performance. This work provides a promising strategy for designing high-performance solid-state Na-CO2 batteries.

Incorporating TiO2 nanocages into electrospun nanofibrous membrane for efficient and anti-fouling membrane distillation

In this study, TiO2 nanocages with a hollow structure were integrated into the polyvinylidene fluoride co-hexafluoropropylene (PH) spinning solution, leading to the fabrication of a novel PH/TiO2 electrospun nanofiber membrane (PH/TiO2 ENM) through electrostatic spinning. The incorporation of TiO2 nanocages resulted in the formation of abundant micro-nano structures on the PH nanofiber surface, enhancing membrane roughness and hydrophobicity. Additionally, the hollow nanostructure of TiO2 nanocages effectively reduced the thermal conductivity of the ENMs. This reduction in thermal conductivity mitigated the temperature polarization effect, thereby increasing mass transfer driving force for the ENMs. The maximum water flux of the PH/TiO2 ENM reached ∼57.9 L m−2 h−1 (LMH), which was approximately 3.7 times higher than that of the original PH ENM. In addition to the formation of micro-nano structures on PH nanofibers, the presence of TiO2 nanocages facilitated the attachment of more low-surface-energy FAS molecules, improving the resistance of them to fouling and anti-wetting properties against both inorganic and organic contaminants, even in the presence of SDS, in a composite feed solution during the DCMD process. Moreover, even after prolonged exposure to a composite salt solution, this membrane also exhibited exceptional anti-fouling properties and stable desalination performance during a 168 h long-term stability test.

Multiple protective layers for suppressing Li dendrite growth and improving the cycle life of anode-free lithium metal batteries

Anode-free lithium metal batteries (AFLMBs) have sparked considerable attention in recent years because of their potential for high energy density; however, they suffer from severe Li dendrite growth and unstable solid electrolyte interphase (SEI), which typically result in rapid capacity decay. Herein, we demonstrate a long-life anode-free pouch cell by designing a dual-coating protective layer (Cu-Sn@SFPH) electrode with Sn-coated Cu (denoted as Cu-Sn) as the bottom layer and SrF2 nanoparticles strengthened by poly (vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) as the top layer. The in-situ formed LiF-rich SEI enables fast Li+ transfer, while the lithiophilic Li-Sn and Li-Sr alloy layers serve as nucleation seeds for uniform Li deposition. The dual-coated Cu electrode in the Cu-Sn@SFPH||Li cell exhibits remarkable cycling stability for more than 3,200 h at a capacity of 2 mAh cm−2. The NCM111||Cu-Sn@SFPH pouch cell demonstrates outstanding performance with a capacity retention of 72.1 % and an average Coulombic efficiency (CE) of 99.9 % for 120 cycles. Under practical conditions, with NCM cathodes and a lean electrolyte volume, this design strategy opens a new approach to AFLMBs.

Polyisobutylene Encapsulated PEDOT: Pss Electrode Honeycomb Skeleton Electrolyte for Moisture Resistant Electro‐Ionic Soft Artificial Muscles

AbstractAdvances in electro‐ionic soft actuators hold significant potential as next‐generation bioelectronic interfaces due to mechanical compliance and operation in agreement with soft biological tissues and low voltages. However, current devices call for encapsulation strategies to accommodate high mechanical demands and long‐term stability in environmental changes. In this study, a durability of polyvinylidene‐fluoride‐co‐hexafluoropropylene (PVDF‐co‐HFP) honeycomb skeleton electrolyte encapsulated with a biocompatible polyisobutylene (PIB) thin film is being investigated. A low water vapor transmission rate (0.61 g m−2 day−1) and elastic modulus (10 kPa) are measured from a 7.5 µm‐thick thin‐modified PIB‐encapsulation layer. The PIB‐encapsulated soft actuator maintains 68% of its mechanical durability after 40 000 cycles of zero‐to‐tension fatigue loading at room temperature. A cantilever actuation test of the PIB‐encapsulated 3mm‐wide 30mm‐long actuator film shows a large tip displacement (15.90 mm) at a low voltage (±1.5 V) under 0.1 Hz, 37 °C, 50% relative humidity (RH). Most importantly, while the unencapsulated actuator immediately degrades in a few cycles at 37 °C, 50%RH, and 0.1% applied strain, PIB‐encapsulated soft actuator performs up to 6500 dynamic actuation cycles without any functionality degradation. Exceptional durability against mechanical fatigue and stability at elevated temperature and humidity meet the prerequisite for future soft biomedical robots that enable long‐lasting safe operations.

Beads-on-string structural nanofiber membrane with ultrahigh flux for membrane distillation

Membrane distillation (MD) is a promising technology among various desalination processes. However, the membrane used in MD is still problematic due to its low permeability and tendency to become wet. In this work, we fabricated a novel electrospun nanofiber membrane (ENM) with micro-nano structures resembling beads on a string to enhance water flux and anti-wetting properties in MD desalination. The composite ENM consists of a heat-conducting top layer made of polyvinylidene fluoride co-hexafluoropropylene (PH) nanofibers embedded with carbon sphere (CS) nanoparticles and a heat-insulating support layer made of pH nanofibers. The PH/CS top layer with beads-on-string micro-nano structures can not only provide a rough surface to elevate anti-wetting property of the membrane, but also create a maximum temperature difference inside the membrane to improve mass transfer of water vapor. The PH/CS composite ENMs acquired the highest water flux of ∼ 71.3 L m−2 h−1 at a temperature difference of 40 °C, and its salt rejection rate for a 3.5 wt% NaCl solution was higher than 99.9% in direct contact membrane distillation. Meanwhile, the composite ENM exhibited long-term stability of 5100 min. Our work presents a novel composite ENM with great potential for promoting water flux and anti-wetting properties towards MD desalination.

Structural, optical, and thermal studies of Poly(vinylidene fluoride-co-hexafluoropropylene) and Polyvinylpyrrolidone composite doped Ag/ZnO mixed nanoparticles for flexible optoelectronic devices

Polymer nanocomposites (PNCs) films based on Polyvinylidene fluoride co-hexafluoropropylene (PVDF-HFP), Polyvinylpyrrolidone (PVP), and Ag/ZnO nanoparticles have been prepared using solution casting technique. Investigation of prepared films has been created using various experimental techniques. These prepared films were characterized by XRD, FTIR, UV–visible, and DSC/TGA analysis to study their structural, optical, and thermal properties. The Enhanced amorphous nature of PVDF-HFP/PVP blend film due to doping has been identified from X-ray diffraction analysis. The FTIR spectra confirmed the complexation between the Ag and ZnO ions and the host polymer in terms of changes in intensity and certain band positions. The UV–visible analysis showed that the optical band gap (direct and indirect band gap) of the pristine polymeric blend change significantly with the concentration of dopant Ag/ZnO NPs, and these effects are more noticeable at the higher loading. Variation in glass transition temperature (Tg) and melting temperature (Tm) of PVDF-HFP/PVP-Ag/ZnO PNCs system having various concentration of Ag/ZnO NPs were observed by DSC analysis. The Tg of the composite has been found to be decreasing with increase in the content of Ag/ZnO NPs revealing the ordered arrangement of nanoparticles in the blend. The excellent thermal stability of the blend nanocomposite compared to pure PVDF-HFP/PVP blend and its improvement with the loading of Ag/ZnO NPs has been proved by TGA. From all the characterization results, Ag/ZnO-doped PVDF-HFP/PVP polymer blend exhibits better properties which are more suitable for electrochemical devices.

Efficient Mineralization of Fluoroelastomers Using Superheated Water in the Presence of Potassium Hydroxide.

The mineralization of fluoroelastomers (FKMs) in superheated water in the presence of potassium hydroxide (KOH) was investigated with the aim of developing a methodology for recycling the fluorine element. Two FKMs-an "uncrosslinked FKM", representing a poly(vinylidene fluoride-co-hexafluoropropylene) (poly(VDF-co-HFP)) copolymer with a VDF/HFP molar ratio of 78/22 and a "crosslinked FKM" consisting of this copolymer (cured by peroxide) and carbon black-were treated. The fluorine content of these FKMs was efficiently transformed into F- ions in the reaction solution using low KOH concentrations (0.10-0.50 M) at 200-250 °C. When the uncrosslinked or crosslinked FKMs reacted with aqueous KOH (0.20 M) at a rather low temperature (200 °C) for 18 h, the fluorine content of these FKMs was completely mineralized (both F- yields were 100%). Although the crosslinked FKM contained carbon black, the fluorine mineralization of the FKM was not inhibited. The addition of Ca(OH)2 to the reaction solutions after the superheated water treatment at 250 °C for 6 h with aqueous KOH (0.50 M) led to the production of pure CaF2, identified using X-ray spectroscopy, with 100% and 93% yields for the uncrosslinked and crosslinked FKMs, respectively.

Preparation and Characterization of a LiFePO4- Lithium Salt Composite Cathode for All-Solid-State Li-Metal Batteries

This study develops a composite cathode material suitable for solid-state Li-ion batteries (SSLIB). The composite cathode consists of LiFePO4 as the active material, Super P and KS-4 carbon materials as the conductive agents, and LiTFSI as the lithium salt. An LiFePO4/LATP-PVDF-HFP/Li all-solid-state LIB was assembled using Li1.3Al0.3Ti1.7(PO4)3 (LATP)/ poly(vinylidenefluoride-co-hexafluoropropylene (PVDF-HFP) as the solid-state electrolyte and lithium metal as the anode. The structure of the synthesized LATP was analyzed using X-ray diffraction, and the microstructure of the composite cathode and solid electrolyte layer was observed using a field emission scanning electron microscope. The electrochemical properties of the all-solid-state LIB were analyzed using electrochemical impedance spectroscopy (EIS) and a charge–discharge test. The effect of the composition ratio of the fabricated cathode on SSLIB performance is discussed. The results reveal that the SSLIB fabricated using the cathode containing LiFePO4, Super P, KS-4, PVDF, and LiTFSI at a weight ratio of 70:10:10:7:3 (wt.%) and a LATP/PVDF-HFP solid electrolyte layer containing PVDF-HFP, LiTFSI, and LATP at a weight ratio of 22:33:45 (wt.%) exhibited the optimal performance. Particularly, the SSLIB fabricated using the cathode containing 3% LiTFSI exhibited a discharge capacity of 168.9 mAhg−1 at 0.1 C, which is close to the theoretical capacity (170 mAhg−1), and had very good stability. The findings of this study suggests that the incorporation of an appropriate amount of LiTFSI can significantly enhance the electrochemical performance of SSLIB batteries.

Enhanced dielectric and electrical performance of phosphonic acid-modified tantalum (Ta)-doped potassium sodium niobate (KNaNbO3)-P(VDF-HFP) composites.

PA-KNNT-P(VDF-HFP) composite films were synthesized using facile solution casting technique. Due to their wide range of applications in dielectric and electrical systems, phosphonic acid (PA)-modified tantalum-doped potassium sodium niobate (KNNT)-polyvinylidene fluoride co-hexafluoropropylene P(VDF-HFP) composite films have piqued the interest of academic researchers. Microstructural analysis showed that PA layers incorporated onto the KNNT particles within the polymer matrix. The PA-KNNT-P(VDF-HFP) composite exhibited improved dielectric and electrical performance over a broad range of frequency, and the value of the dielectric constant of the P(VDF-HFP) composites is improved by ≈119 over the P(VDF-HFP) matrix at a filler loading 19 wt.%. Moreover, PA-KNNT-P(VDF-HFP) composite also reveals higher dielectric constant (≈ 119) and AC conductivity than P(VDF-HFP)-KNNT composites, while maintaining suppressed dielectric loss ([Formula: see text] at 102Hz). It is also observed that the PA-KNNT-P(VDF-HFP) composite exhibited an insulator-conductor transition with a percolation threshold of fKNNT = 13.4 wt.%. As a result of their exceptional dielectric and electrical characteristics, PA-KNNT-P(VDF-HFP) composites have the potential to find exciting practical applications in a variety of electronic domains.

High Specific-Capacity Al-Graphite Dual-Ion Batteries

Rechargeable Al-graphite dual ion batteries are believed as a promising stationary energy storage system due to its low cost and long cycling life. Through engineering both Al and graphite electrodes using poly(vinylidene fluoride) and poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) copolymer as both binder and ionic network, Al-graphite batteries with high specific capacities and rate capabilities were demonstrated. We employed high-surface-area acetylene black (AB) as the substrate for Al plating to enhance the rate capability (up to 20 mA cm−2 geo) and stability (>500 h) of Al plating/stripping. The utilization of graphite was increased by anchoring graphite particles in the PVDF-HFP ionic network. With these Al and graphite electrodes, Al-graphite dual ion batteries were shown to have a specific capacity of ∼140 mAh g−1 C at a current density of 186 mA g−1 C and high cycling stability (∼0.07% decay per cycle based on the fully activated capacity at 2.98 A g−1 C). The 3D electrode design (Al negative and carbon positive electrode) with stable structure and high surface area can facilitate the development of the new Al-based battery chemistries (Al-Cl2, Al-Br2, and Al-O2, etc.).

Efficient fluoride recovery from poly(vinylidene fluoride), poly(vinylidene fluoride-co-hexafluoropropylene) copolymer and poly(ethylene-co-tetrafluoroethylene) copolymer using superheated water with alkaline reagent

Mineralization of poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) [poly(VDF-co-HFP)] copolymer, and poly(ethylene-co-tetrafluoroethylene) copolymer (ETFE) in superheated water in the presence of an alkaline reagent was investigated with the aim of developing a technique to recycle the fluorine element. These polymers underwent almost complete defluorination to form fluoride ions (F–) in the reaction solution at a relatively low temperature (250 °C) under Ar atmosphere. When PVDF was reacted with aqueous KOH (1.0 M) for 6 h, the amount of which corresponds to 10 times the molar amount of fluorine content (as atoms) in PVDF, the yield of F– released into the reaction solution reached 95 %. This transformation was accompanied by the formation of carbon rich reside, which consists of amorphous carbon. In contrast, for a treatment performed with O2 instead of Ar, significant differences were observed in the products: while F– ions efficiently produced in the reaction solution, carbon rich residue did not form and the major species that composed the total organic carbon content in the reaction solution was oxalate. Four consecutive runs (that is, after one reaction at 250 °C under Ar was complete, new PVDF was charged to the reaction mixture and then reacted again) caused no decrease of the F– yield. When treated with aqueous KOH (1.0 M) under Ar at 250 °C for 6 h, poly(VDF-co-HFP) and ETFE copolymers also completely mineralized to form F– ions with 100 and 98 % yields, respectively. Introducing Ca(OH)2 to the resulting reaction solutions of these (co)polymers after superheated water treatment produced pure CaF2, i.e., artificial fluorspar.

Correlating the Macrostructural Variations of an Ion Gel with Its Carbon Dioxide Sorption Capacity

We report on a direct correlation between the macroscale structural variations and the gas sorption capacities of an ion gel. Here, we chose 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide ([Emim][TF2N]) and poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) as the ionic liquid and host polymer, respectively. The CO2 sorption in the thin films of the IL-polymer was measured using the gravimetric method. The results of our experiment showed that the trend in CO2 uptake of these mixtures was nonlinearly correlated with the content of IL. Here, we highlight that the variations in the molecular structure of the polymers were the main reason behind the observed trend. The presented data suggested the possibility of using the composition of mixtures containing IL and polymers to realize a synergistic gain for gas sorption in these mixtures.

Biodegradable and highly conductive polymeric blend based on the latex of Calotropis gigantea as solid electrolyte in energy storage applications

A blend polymer based on the latex of the South-Asian giant milkweed Calotropis gigantea (CGL) combined with poly (vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) at a mass ratio of 1:1 without the addition of doping salts was synthesized via solution casting to prepare an ionic conductive film. The morphology, crystalline state, vibrational and thermal properties of the film were investigated by Scanning electron microscopy, X-ray diffraction, Fourier Transform infrared spectroscopy (FTIR), Thermal gravimetric analysis (TGA) and Differential scanning calorimetry (DSC). The ionic conductivity and transport properties were investigated by using electrochemical impedance spectroscopy (EIS) Technique. Due the highest ionic conductivity at room temperature (2.7 x 10−2 S/cm), all-solid-state electrolyte was assembled using the prepared polymer film and a comparative study was conducted with respect to 1M H2SO4 liquid electrolyte, regarding the specific capacitance and the electrical properties. The results demonstrate that the fabricated all-solid-state supercapacitor using PVDF-HFP/CGL blend polymer film as electrolyte matches the performance of the liquid electrolyte.

Molecular simulation of poly(VDF-HFP) copolymer with imidazolium-based ionic liquid as an effective medium for biogas separation

The embedding of ionic liquids (ILs) into the polymer membrane matrix affects the morphology and properties of the material. Due to the unique nature of ILs, including high thermal stability and the ability to selectively absorb various gases, polymer-IL systems generally exhibit improved separation properties. In this work, the CO2/CH4 separation properties of poly (vinylidene fluoride-co-hexafluoropropylene)) (poly (VDF-HFP)) with different amounts of 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide ([EMIM] [TFSI]) were simulated by classical molecular dynamics (MD). MD simulations were performed using the GROMACS program with an AMBER force field for various polymer chain lengths (8, 10 and 12 mer) and different IL concentrations (0, 20, 40, 60 and 80 wt%) in the polymer. While the increased affinity of CO2 for the membrane containing a high concentration of IL was observed, the effect of IL on the affinity of CH4 was found to be negligible. A benefit of understanding the mechanism of gas absorption in polymeric-IL systems and revealing the interactions of gas molecules with IL and polymer molecules at the molecular level indicates the potential of MD simulation for understanding processes in membrane gas separations.

Fluorocarbon-Based Selective-Superwetting Nanofibrous Membranes with Ultraviolet-Driven Switchable Wettability for Oil–Water Separation

Selective-superwetting membranes possess controllable wettability and have great potential in the oil–water (OW) separation field. The electrospinning technique has advantages in fabricating nanofibrous materials with distinguishing features such as high porosity and large surface area. However, in recent years, there have been a few studies on preparing photoinduced superwetting membranes by electrospinning. In this study, an ultraviolet-driven selective-superwetting nanofibrous membrane was prepared by electrospinning poly(vinylidene fluoride)-cohexafluoropropylene (PVDF-HFP) blended with fluorinated TiO2 nanoparticles. The wetting behavior of the membrane can be tuned between superhydrophobic/superoleophilic and superhydrophilic/underwater superoleophobic by two processes, ultraviolet (UV) irradiation, and heating, during which the water contact angle (WCA) fluctuates rapidly from 170 to 0° and back to 160°. The reliability of the controllable wettability was proven by a 15-cycle conversion test, and the nanofibrous membrane remained superhydrophobic thereafter. Our results have promising multipurpose applications as an effective and flexible solution to more complex oil–water mixtures in wastewater abatement.

Engineering beads-on-string structural electrospun nanofiber Janus membrane with multi-level roughness for membrane distillation

A novel Janus membrane was fabricated by constructing a thin hydrophobic layer with beads-on-string structure on the surface of superhydrophilic polyacrylonitrile (PAN) electrospun nanofiber (ENs) substrate through hybrid electrospinning and electrospraying techniques. The electrosprayed polystyrene/poly(dimethylsiloxane) (PS/PDMS) beads were interlinked by nanofibers and further anchored by 3-D network formed by electrospinning polyvinylidene fluoride-co-hexafluoropropylene (PH). Surface roughness and morphology of formed beads and relevant hydrophobic layers could be highly affected by weight ratios and concentrations of PS and PDMS. The hydrophobic layer (PH-7PS/7PDMS) prepared by electrospraying PS/PDMS (7 wt%/7 wt%) mixed solution showed the highest water contact angle (WCA) value of 148.5o and the largest surface roughness of 812 nm. The optimized Janus membrane could exhibit a water flux of 27.7 L/m2h and a salt rejection efficiency close to 100 % at the temperature difference of 40 °C when 3.5 wt% sodium chloride (NaCl) was used as the feed solution. The addition of PDMS could endow the Janus membrane with better performance stability and anti-fouling ability due to the enhanced surface hydrophobicity and formation of unique multi-level roughness on the hydrophobic layer. The prepared Janus membrane could be used as a promising candidate for the direct contact membrane distillation (DCMD) process.

Molecular Engineering of Biorefining Lignin Waste for Solid-State Electrolyte

Lignin is the second most abundant renewable biopolymer on Earth but also a waste in both the paper industry and lignocellulosic biorefineries. Recently, lignin valorization has been extensively sought after to return economics, enhance carbon efficiency, and improve the bioeconomy, but the commercial value and size compatibility still hinder its applications. In this study, we developed a facile strategy to apply lignin waste into a solid-state electrolyte (SSE), which represents a safe next generation energy storage. Lignin was grafted with polyethylene glycol (PEG), an efficient lithium-ion (Li+) conductive polymer, to enable its ion conduction. The synthesized PEG-g-lignin was mixed with poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) and PEG-g-lignin-based bis(trifluoromethanesulfonyl)imide (LiTFSI) to prepare a solid polymer electrolyte (SPE), which has an ionic conductivity of 2.5 × 10–5 S/cm at 25 °C. This result was further enhanced to 6.5 × 10–5 S/cm by adding an ion-conductive ceramic of Li6.4La3Ga0.2Zr2O12 (LLGZO), which is referred to as composite polymer electrolyte (CPE). These data represent the highest ones among reported polymer-based SSE. A mechanistic study by using 2D HSQC NMR revealed that PEG-g-lignin has increased ether type β–O–4 linkages that can promote the interchain hopping of Li+ between lignin polymer chains, and 31P NMR revealed that the lignin phenolic end can be associated by Li+. Moreover, the abundant aromatic moieties and methoxyl in PEG-g-lignin also enhanced Li+ association and improved its ionic conductivity. The superior ionic conductivity of PEG-g-lignin-based SSE can enable massive applications of this biorefining waste in all-solid-state lithium batteries (ASSLBs), which has potential to promote the energy sector by promoting the bioeconomy and enhancing the renewability and sustainability of future energy storage.