Conductivity Of Composite Membranes Research Articles

Dual-aeolotropic electrically conductive flexible composite membrane with enhanced red fluorescence

New-typed dual-aeolotropic conductive flexible composite membrane (DCFCM), was devised and fabricated by parallel electrospinning. DCFCM consists of two layers that are strongly coupled to form a top-to-bottom structure. Janus nanoribbon (JN), possessing two distinct sides (respectively conducting and insulating-fluorescent side), is highly oriented in each layer of DCFCM. The top-to-bottom structure of DCFCM effectuates the macro-level zoning, and the JN as a conductive and constitutive function in DCFCM realizes the micro-level zoning, which achieves the combination of microstructure and macroscopic structure in DCFCM. Thus, DCFCM simultaneously performs dual-aeolotropic electrical conduction and enhanced red luminescence due to the partitioning structures which aid in minimizing adverse interactions between the conductive and luminescent materials. The conducting anisotropy of each layer in the DCFCM can be adjusted by varying the PANI content. The conductance ratio can reach 108 when the PANI content is 60–70 %. Additionally, DCFCM exhibits strong red emission, originating from the allowed 5D0→7F2 (593 nm), 5D0→7F2 (616 nm) energy levels transitions of Eu3+ ions. This work provides a simple and effective method to fabricate aeolotropic conductive membranes with novel multifunctional properties.

Dual-Aeolotropic Electrically Conductive Flexible Composite Membrane with Enhanced Red Fluorescence

Dual-Aeolotropic Electrically Conductive Flexible Composite Membrane with Enhanced Red Fluorescence

High performance and robust durability proton conductive composite membranes containing CeO2-TiC incorporated sulfonated poly(arylene ether) for hydrogen fuel cells

Degradation of proton exchange membrane (PEM) due to free radicals often decreases the overall performance of proton exchange membrane fuel cells (PEMFC). The incorporation of antioxidative additives into the polymer matrix has been widely exploited to mitigate oxidative degradation but is still challenging. Herein, butylsulfonated poly(arylene)(SAFPAE) was synthesized by polycondensation followed by nucleophilic substitution and highly crystalline CeO2-TiC filler was prepared by simple hydrothermal process. SAFPAE alleviates the problematic characteristics of proton-exchange membranes (PEMs) whereas CeO2 scavenges free radicals and TiC improves tensile strength. Variable weight ratios of CeO2-TiC were blended into the SAFPAE matrix to study its physicochemical, and electrochemical properties. The random distribution of CeO2-TiC in the SAFPAE matrix enhanced thermal and mechanical strength and increased water absorption, ion exchange capacity, as well as proton conductivity. Specifically, SAFPAE/CeO2-TiC (1.0wt%) exhibited a current output of 0.18Acm−2 and a power output of 0.087 Wcm−2 at 20% RH and 60°C. It also experienced a degradation of 0.145mVh-1 over 1100hours of operation. Under operating conditions of RH 20% and 60°C, PEMFCs with an SAFPAE/CeO2-TiC (1.0wt%) membrane exhibited significantly improved performance and enhanced durability compared to PEMFCs with pure SAFPAE and without sacrificing their cell performance.

Enhanced lanthanum and cerium removal of self-powered electro-membrane bioreactor (SPEMBR) using high-active bi-functional M-N-CNTs@Fe/Mo electrode

Lanthanum and cerium are widely used as important raw materials for energy storage batteries due to excellent natural electrical, magnetic, and optical properties. However, with the explosive growth of new energy generation and the environmental degradation-resistant of lanthanum and cerium, it is difficult to balance environmental sustainability and resource scarcity to achieve lanthanum-cerium removal by conventional chelate salt precipitation. Herein, a laboratory-scale self-powered electro-membrane bioreactor (SPEMBR), integrating high-active nitrogen-doped carbon nanotube-loaded iron and molybdenum bimetallic conductive composite electrode membrane (M−N−CNTs@Fe/Mo) by hydrothermal and phase inversion processes was successfully constructed and evaluated for removing lanthanum cerium from industrial wastewater. The prepared bi-functional M−N−CNTs@Fe/Mo5% electrode membrane exhibited a uniform morphology and excellent hydrophilicity, with nano pore lattice spacing only 0.2637 nm. Electrochemical test results demonstrated that the novel electrode indicated excellent redox properties (i0 = 8.35 × 10−3 A cm−2, Cdl = 1.13 mF cm−2) and efficient electron transfer efficiency (Rct = 4.69 Ω, n = 3.9). Based on optimized conditions (5)% doping ratio, pH = 10, C = 20 mg/L), the SPEMBR assisted by M−N−CNTs@Fe/Mo catalytic electrode membrane achieved approximately complete removal efficiency of lanthanum and cerium (>99.2 %), superior to most publicly available related studies (86.3 %-99.0 %), but with a calculation cost of only $8.54. Identification of membrane interface products and system precipitates demonstrated that the outstanding removal efficiency was attributed to the combined reaction mechanism of electroreduction, electrocoagulation and electromembrane filtration. This work provides a bright application prospect for low-cost and effective removal of lanthanum cerium metal based on electrode membranes.

Robust and highly proton conductive COF composite membranes for fuel cell and electrochemical hydrogen compression

Robust and highly conductive proton exchange membrane (PEM) is the unremitting pursuit of numerous electrochemical energy technologies such as fuel cell and the emerging electrochemical hydrogen compression. Ionic covalent organic framework nanosheets (iCONs) with long-range ordered nanochannels and abundant ionic groups show substantial potential as next-generation PEM materials. However, it is challenging to assemble iCONs into membranes with both robustness and flexibility due to the electrostatic repulsion and rigid framework. Herein, we propose a hydrogen-bond binding strategy to fabricate sulfonic iCON (SCON) composite membranes by co-assembling tannic acid (TA) nanoaggregates and SCONs. The abundant and dynamically reversible hydrogen-bond interactions introduced by TA nanoaggregates establish effective linkage between SCONs and allow some restricted movements, endowing membranes with remarkably improved mechanical properties. The stacked SCONs construct long-range ordered nanochannels with well-arranged sulfonic groups in membranes, and the hydrogen-bond networks further facilitate the proton transport through Grotthuss mechanism. Consequently, TA/SCON composite membranes displays significantly enhanced tensile strength of 101.9 MPa, good flexibility and high proton conductivity of 490.1 mS cm−1 at 80 °C and 100 % RH simultaneously. This hydrogen-bond binding strategy offers a promising approach to fabricate robust and highly conductive PEMs for various proton-conducting applications.

Conductive and auxetic composite membranes based on graphene nanoplatelets and polybutylene succinate produced via electrospinning

AbstractThis work presents a method to produce conductive and auxetic composite membranes from a biobased and biodegradable matrix: polybutylene succinate (PBS). The conductivity was improved by the addition of graphene nanoplatelets (GNP) and the samples were produced via solution electrospinning. The membrane properties were shown to increase with increasing GNP concentration and the rotational speed of the collector. In particular, a membrane having 0.2% w/v GNP and fabricated at the highest collector speed (9.96 m/s) showed the highest electrical conductivity (1.56 × 10−4 S/m) while having a negative Poisson's ratio (NPR) of −1.5 in tension. To complete the analysis, mechanical characterizations showed that the presence of GNP led to a substantial increase in Young's modulus (234%) and tensile strength (190%) compared to the neat PBS membrane produced under the same conditions. Differential scanning calorimetry (DSC) revealed a slight crystallinity increase since GNP are acting as heterogeneous nucleating agents, while thermogravimetric analysis (TGA) showed an improved thermal stability for the GNP/PBS membranes. This unique combination of auxetic and conductive properties can be useful for a wide range of innovative applications such as electronic devices, smart textiles, biomaterials, and biomedical devices.Highlights Electrospinning was successful to produce polybutylene succinate (PBS) nanofibers. A careful control of the processing conditions led to auxetic fiber mats. Electrically conductive mats were produced by adding graphene nanoplatelets (GNP) to PBS. The PBS mechanical properties were highly improved (200%) with low GNP content (0.2%).

Conductive and self-cleaning composite membranes from corn husk nanofiber embedded with inorganic fillers (TiO2, CaO, and eggshell) by sol–gel and casting processes for smart membrane applications

Abstract The utilization of corn husk as a renewable bio-cellulose material for producing bio-composite membranes through wet chemical and sol–gel process offers numerous advantages. It is an abundant, inexpensive, nontoxic, and readily available agricultural waste product. To enhance the properties of bio-composite membranes, various particulate ionic fillers such as titanium dioxide, calcium oxide, and eggshell (as a source of calcium carbonate) are incorporated in different weight percentages (0, 1, and 5%). These fillers act as additives to the corn husk nanofiber mixed with polyvinyl alcohol during the formation of the biomembrane. The resulting biocomposite membranes exhibit several desirable characteristics. They are lightweight, easy to shape, biodegradable, nontoxic, and possess excellent physical, mechanical, thermal, and electrical properties. Moreover, the addition of 5 wt% of eggshell powder leads to an increase in the dielectric constant and electrical conductivity, reaching approximately 3.300 ± 0.508 and 1.986 × 103 (Ω·m)−1, respectively. These measurements were taken at a frequency of 500 Hz and a temperature of 27°C. Furthermore, these membranes demonstrate self-cleaning abilities due to a contact angle greater than 90°. The electrical properties of the biocomposite membrane improve with a higher percentage of inorganic filler, making them suitable for applications in smart membranes, as well as mechanical, electrical, and thermal systems.

Thermally Conductive, Superhydrophobic, and Flexible Composite Membrane of Polyurethane and Boron Nitride Nanosheets by Ultrasonic Assembly for Thermal Management

Thermal management is of significance for modern electronic products, and it remains challenging to keep the cooling performance of thermal management materials in multi-environment applications from being unaffected by external contamination. Herein, we constructed thermally conductive, superhydrophobic, and flexible composites using thermoplastic polyurethane electrospun membrane as a nano-fibrous substrate, hexagonal boron nitride nanosheets as a conducting filler, and polydimethylsiloxane/SiO2 nanoparticles for hydrophobization. The composite membrane demonstrated outstanding thermal management performance with an ultrahigh thermal conductivity (TC) of 7.193 W/m K. The membrane is flexible with durable TC even after 500 bending and stretching cycles and possesses superhydrophobicity with a water contact angle greater than 165° and a slide angle lower than 2.7°, which prevents the surface from being stained and protects its excellent TC for long-term applications, favoring thermal management of modern electronic products.

A photothermal and conductive composite hydrogel membrane for solar-driven synchronous desalination and salinity power generation

A calcium alginate hydrogel and nickel foam composite membrane (CHN) can achieve desalination and salinity gradient power generation by solar energy. The CHN membrane can be used as a universal solar conversion platform to obtain blue energy.

Facile bottom-up synthesis of reduced graphene oxide/aramid nanofiber composite films with high thermal conductivity

Thermal management materials with high thermal conductivities, heat resistances, and excellent mechanical properties are urgently required for application in modern electronic power systems. The mechanical properties and high-temperature resistance of thermally conductive materials can be improved by using aramid nanofibers as thermally conductive substrates. In this study, para-aramid nanofibers (ANFs) were synthesized using a greener, time-efficient, and high-yield bottom-up method. Water-dispersible reduced graphene oxide (rGO) was combined with the ANFs to prepare a highly thermally conductive composite membrane with nacre-like structures by vacuum filtration. The rGO-50/ANF showed a remarkably high thermal conductivity (18.28 W m−1 K−1) and excellent tensile strength (60.2 MPa) with a strong penchant for high-temperature applications (>200 °C). In particular, the composite film can significantly reduce the surface temperature of light-emitting diode lamps in practical thermal management applications, indicating its excellent thermal management performance.

High performance flexible and antibacterial strain sensor based on silver‑carbon nanotubes coated cellulose/polyurethane nanofibrous membrane: Cellulose as reinforcing polymer blend and polydopamine as compatibilizer

In this study, ethyl cellulose was used as the second-phase polymer blended with polyurethane to make nanofibrous membrane as antibacterial strain sensor. The results indicated that ethyl cellulose could regulate the morphology of polyurethane through strong hydrogen bonding, which observably enhanced the nanofiber uniformity of polyurethane. Furthermore, rigid cellulose also remarkably improved the mechanical strength and thermal stability of the nanofibrous membrane. After being coated with silver nanoparticles and carbon nanotubes assisted by polydopamine (PDA), the membrane with outstanding bacteria inhibition performance exhibited outstanding sensitivity toward external mechanical stretching, as well as real-time motion of human body parts. The conductive composite membrane possessed sensitive and regular resistance feedback to 100 cycles of varied human motions. The cellulose in the nanofiber structure ensured the shape recovery and longtime use stability of the membrane. This study proposed a novel thinking for the construction of high performance strain sensor by rational introduction of rigid polysaccharide into the polymer matrix.

Preparation of Shell/Core Atypical Spiral Conductive Microfibers and Composite Membrane with Good Conductivity and Mechanical Properties

AbstractPoly(3,4‐ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) core–shell conductive atypical spiral microfibers are prepared based on microfluidic spinning technology (MST). The formation mechanism of the special‐shaped spiral structure is analyzed. The microfibers and polydimethylsiloxane (PDMS) are composited into membranes, and the microfibers and composite membranes are characterized. The research results show that the conductivity of shell conductive bulbine‐torta (BT) microfibers and the composite membrane are 0.125 1 and 0.880 2 s cm−1, respectively. The maximum strain of a single PEDOT: PSS core–shell conductive BT microfibers is 36.92% under a stress of 213.10 kPa, and the maximum strain of the composite membrane is 107.46% under a stress of 470.56 kPa, indicating that the composite membrane can effectively improve the properties and practicability of the conductive fiber. The change of resistivity of the composite membrane in the stretched state is observed, and it is found that the resistivity first steadily increases and then increases exponentially, indicating that composite membrane has potential application prospects in the fields of thin membrane sensors, electronic skins, smart wearable textiles, etc.

Antifouling Conductive Composite Membrane with Reversible Wettability for Wastewater Treatment.

Membrane fouling severely hinders the sustainable development of membrane separation technology. Membrane wetting property is one of the most important factors dominating the development of membrane fouling. Theoretically, a hydrophilic membrane is expected to be more resistant to fouling during filtration, while a hydrophobic membrane with low surface energy is more advantageous during membrane cleaning. However, conventional membrane materials do not possess the capability to change their wettability on demand. In this study, a stainless steel mesh–sulfosuccinate-doped polypyrrole composite membrane (SSM/PPY(AOT)) was prepared. By applying a negative or positive potential, the surface wettability of the membrane can be switched between hydrophilic and relatively hydrophobic states. Systematic characterizations and a series of filtration experiments were carried out. In the reduction state, the sulfonic acid groups of AOT were more exposed to the membrane surface, rendering the surface more hydrophilic. The fouling filtration experiments verified that the membrane is more resistant to fouling in the hydrophilic state during filtration and easier to clean in the hydrophobic state during membrane cleaning. Furthermore, Ca2+ and Mg2+ could complex with foulants, aggravating membrane fouling. Overall, this study demonstrates the importance of wettability switching in membrane filtration and suggests promising applications of the SSM/PPY(AOT) membrane.

Ultralight, Safe, Economical, and Portable Oxygen Generators with Low Energy Consumption Prepared by Air-Breathing Electrochemical Extraction.

Pure oxygen is vital in medical treatment, first aid, and chemical synthesis. Hypoxia can cause severe damage to the organ systems such as respiratory, digestive, and nervous systems and even directly cause death. Notably, the severe Coronavirus disease 2019 (COVID-19) pandemic has exacerbated the shortage of medical oxygen in the world. Hence, a safe, economical, and portable oxygen supply device is urgently needed. Here, we have successfully prepared a device with air-breathing electrochemical extraction of pure oxygen (ABEEPO) with light weight and high energy efficiency. By renovating the structure of the electrolytic cell, the components bipolar plate and end plate are replaced with a plastic membrane, and the component current collector is replaced with a highly conductive graphene composite membrane electrode. Due to the use of the plastic membrane and graphene composite membrane electrode, the weight of the electrolytic cell is reduced from 1319.4 to 1.6 g, and the flexibility of the electrolytic cell is successfully realized. Through optimizing anode catalysts, working area, and operating voltage, a high flow rate per mass (234 mL h-1 g-1) was achieved at a voltage of 1.2 V. The device exhibits high stability in 2 h. The new portable oxygen production device would be effective for hypoxia treatment.

Ultrahigh proton conductive nanofibrous composite membrane with an interpenetrating framework and enhanced acid-base interfacial layers for vanadium redox flow battery

Sulfonated poly(ether ether ketone)-based membranes containing amphoteric functionalized nanofibrous network (SP@f) with the three-dimensional interlaced structure were developed, and the acid-base interaction between SP@f and SPEEK constructs highly conductive proton channel and compatible interfaces. The large specific surface area and aspect ratio of nanofibers afford an orientated ion transmission channel along the fiber axis, bringing a high concentration of proton carriers and abundant hydrogen bonds to transfer proton. The S/SP@f-10 composite membrane displays superior proton conductivity (37.8 mS cm −1 ) to pristine SPEEK (16.4 mS cm −1 ) and Nafion 212 (28.0 mS cm −1 ). Owing to the interconnected network structure of SP@f and the acid-base interactions, ion selectivity and chemical stability of the S/SP@f-10 composite membranes improve seriously. VRFB single cell with S/SP@f-10 membrane shows better voltage efficiencies (VE: 93.0–74.0%) and energy efficiencies (EE: 87.5–73.0%) than that of pristine SPEEK (VE: 86.0–60.2%, EE: 82.1–58.0%) and Nafion 212 membrane (VE: 88.0–67.0%, EE: 80.0–63.9%) at 60–200 mA cm −2 . Meanwhile, S/SP@f-10 maintains a stable EE value of 80.0%, and no obvious decay after 500 cycles at 150 mA cm −2 appears, demonstrating its outstanding structural stability and durability. This opens a facile method to prepare the high-performance membrane by constructing the directional proton channels with functionalized nanofibers. To solve the tradeoffs between ion selectivity and conductivity, amphoteric functionalized nanofibrous network along with an orientated ion channel was constructed, and the interface layer occupied with acid-base pairs generates good structural stability, chemical stability and excellent VRFB performance. • Amphoteric functionalized nanofibrous network (SP@f) contains 3D interlaced structure. • Nanofiber interface layer formed by acid-base pairs provides high concentration of proton carriers. • Ultra-high proton conduction depends upon the long and continuous proton transport channel. • S/SP@f-10 membrane shows outstanding battery efficiencies and long-term cycle stability.

Silk fibroin/polycaprolactone-polyvinyl alcohol directional moisture transport composite film loaded with antibacterial drug-loading microspheres for wound dressing materials

Drug delivery technology can prevent wound infection and inflammatory reactions and accelerate wound healing and quality. In this paper, we propose preparing a multifunctional medical dressing to meet the various needs of people for dressing. A multi-layered composite nanofiber membrane was constructed using silk fibroin as the substrate, and mesoporous silica nanoparticles (MSN) with high adsorption properties were first prepared and then electrosprayed on silk fibroin (SF)/chitosan (CS) microspheres to form MSN-SF/CS microspheres with uniform distribution. Then the MSN-SF/CS microspheres were sprayed on the silk fibroin (SF)/polycaprolactone (PCL)-polyvinyl alcohol (PVA) unidirectional water-conducting composite nanofiber membrane. The test results showed that the encapsulation rate of bovine serum albumin (BSA) by MSN-SF/CS drug-loaded microspheres was 65.53% and the cumulative release rate in vitro was 54.46%. The results of in vitro experiments also showed its good antibacterial effect and good biocompatibility. To eliminate excess wound exudate and reduce inflammation, the cumulative unidirectional transport capacity (AOTC) of 651.75% was achieved by spraying the microspheres on an SF/PCL- PVA unidirectional water conductive composite membrane. This study could stimulate and promote the use of additional wound healing biomaterials in clinical medicine.

Porous gC3N4–Gd2Zr2O7 enables the high-temperature operation of Nafion membranes in polymer electrolyte fuel cells over 500 hours

Porous and antioxidative gC3N4–Gd2Zr2O7 facilitates a highly conductive Nafion composite membrane, leading to efficient and durable performance in high-temperature polymer electrolyte fuel cells.

Proton Conductive Composite Membranes with Stable Anisotropic Though-Plane Conductivity: A New Preparation Approach

In common PEMFCs, a polymer electrolyte membrane selectively conducts protons but blocks passage of electrons and reactants. Nafion, current benchmark membrane material, offers a superior conductivity owing to unique morphology comprising randomly oriented elongated ionic nanochannels within a Teflon-like matrix. Nanochannel orientation is a promising approach to enhance Nafion conductivity, yet there has been no facile method to induce a strong and stable alignment within membranes in the most desired through-plane (TP) direction.Here we report a novel and facile preparation approach based on dual electrospun Nafion-PVDF nanofiber composite that yields a stable TP alignment. The preparation starts from electrospinning of a mixed fiber mat, which is subsequently converted to a solid membrane by plunging the mat into a thin slit. Due to extreme thinness, the electrospun nanofiber readily buckle into a folded structure, thereby a strong inherent microscopic channel orientation within nanofibers is readily converted to macroscopic TP channel alignment. Ultimately, the folded nanofibers fuse, consolidating the membrane.A pronounced TP alignment of ion channels in the membranes, sustaining fusion and annealing, is demonstrated using TEM and SAXS. The analysis also highlights the importance of PVDF fiber as a stabilizing and confining component. Electrospun PVDF fibers within consolidated Nafion-PVDF composite preserve channel orientation upon annealing both in TP and in-plane (IP) aligned membranes, while pure Nafion membranes, similarly prepared from electrospun Nafion fibers, rapidly lose structural anisotropicity. Finally, the impedance measurements demonstrate highly anisotropic conductivity of both TP- and IP-aligned membranes, consistent with their anisotropic structure. Thus, measured TP conductivity of TP-aligned 46% Nafion composite is nearly three times its IP conductivity and about 70% that of Nafion 212, thereby the conductivity normalized to Nafion content exceeds that of pure Nafion. The approach, still leaving much room for optimization, holds potential to advance PEMFC technology by overcoming current limitations and fully utilizing advantageous features of Nafion membranes. Figure 1

Electrospun Composite Gel Polymer Electrolytes with High Thermal Conductivity toward Wide Temperature Lithium Metal Batteries

Herein, the thermally conductive composite polymer membranes (CPMs) with silica-coated silver nanowires (AgNWs@SiO2) and poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) are first fabricated by an electrospinning technique. Various composite gel polymer electrolytes (CGPEs) are investigated with different weight percentages of AgNWs@SiO2 with respect to PVDF-HFP in the presence of liquid electrolytes. The CPMs display high thermal conductivity and thermal stability, good mechanical strength, and high electrolyte uptake. The thermal conduction property of CPMs was analyzed by a bidirectional asymmetric heat transfer model. Moreover, the CGPEs with the electrospun CPM as the matrix and AgNWs@SiO2 as fillers (es-CGPEs) possess the high ionic conductivity and excellent electrochemical performance compared to the Celgard separator system. The Li/es-CGPEs/LiFePO4 cell shows an enlarged excellent cycling life and better rate performance at 25 and 60 °C, in comparison to the one without AgNWs@SiO2 fillers. Interestingly, the Li/es-CGPEs/LiFePO4 cell in the presence of 5 wt % of AgNWs@SiO2 still delivers an excellent rate capability at 0 °C. The es-CGPE with AgNWs@SiO2 would be a promising candidate as the electrolyte material toward wide temperature lithium metal batteries.

Efficient and durable composite membranes based on polydopamine-mediated sulfonated graphene oxide for direct methanol fuel cells

Polydopamine-mediated sulfonation yields homogeneous and antioxidative modified graphene oxide, facilitating highly conductive and stable composite membrane, which lead to efficient and durable performance in direct methanol fuel cell application.