Teflon Substrate Research Articles

Janus membranes with simultaneous flux enhancement and fouling/wetting resistance prepared by a modified interfacial polymerization process for membrane distillation

Conventional membrane distillation (MD) membranes are hydrophobic and challenged by severe membrane fouling and wetting. Current surface modification strategies for anti-fouling and anti-wetting purposes, usually complex and time-consuming, often compromise the MD flux. Herein, we propose a modified interfacial polymerization (mIP) approach to fabricate Janus membranes with rapid and robust MD performance. In the mIP process, a dry hydrophobic substrate is first immersed in an oil-phase monomer solution and then in contact with an aqueous monomer solution to trigger the mIP reaction. The as-fabricated Janus membrane (e.g., IP2@PTFE) comprised an ultrathin, underwater oleophobic, and defect-free polyamide (PA) layer and a porous polytetrafluoroethylene (PTFE) substrate. Compared with the unmodified PTFE membrane, the vacuum MD flux of the IP2@PTFE membrane held a 177.4 % increase when tackling a NaCl solution (3.5 wt%) at 60 °C. When the NaCl solution contained sodium dodecyl sulfate (SDS) surfactant or/and mineral oil, the IP2@PTFE membrane exhibited fouling and wetting resistance simultaneously; conversely, severe oil fouling and quick SDS-induced wetting occurred on the pristine PTFE membrane. The mIP process does not require any pretreatment of the hydrophobic substrate, so it is facile and scalable. We believe that this study will facilitate the design of robust MD membranes.

Silver nanoparticles/graphene oxide arranged on polytetrafluoroethylene substrate hydrophilic modified with TiO2 to construct efficient air purification material

Recently, the harsh air environment caused by disasters and human activities poses a great challenge to the development of efficient and antibacterial air purification systems to protect human health. In this work, a new type of high-efficiency polytetrafluoroethylene (PTFE) air filter was successfully prepared by employing silver nanoparticles decorated with graphene oxide (Ag NPs/GO) functional materials that deposited in PTFE substrate membranes hydrophilic modified with TiO2 for the improvement of the enclosed space air quality. The results revealed that the introduction of TiO2 can improve the interfacial adhesion between PTFE membrane and functional materials, improving the feasibility of long-term application of composite membrane. The composite membrane possessed the crisscross network structure interconnected by fibrils, which gives the membrane high-efficiency particulate matters (PMs) removal rate (99.25% for PM2.5) without sacrificing the pressure drop (90.52 Pa). Moreover, the prepared composite membrane also has more excellent antibacterial performance (98.7% for Escherichia coli (E. coli)), which can reduce the secondary pollution caused by improper post-treatment of the polluted filter in practical applications. After simple cleaning and regeneration, the composite membrane can still maintain an ultra-high particle removal rate (over 95%) after 5 cycles. The prepared efficiency air filtration composite membranes have positive potential applications in air purification.

SERS with Flexible β-CD@AuNP/PTFE Substrates for In Situ Detection and Identification of PAH Residues on Fruit and Vegetable Surfaces Combined with Lightweight Network.

The detection of polycyclic aromatic hydrocarbons (PAHs) on fruit and vegetable surfaces is important for protecting human health and ensuring food safety. In this study, a method for the in situ detection and identification of PAH residues on fruit and vegetable surfaces was developed using surface-enhanced Raman spectroscopy (SERS) based on a flexible substrate and lightweight deep learning network. The flexible SERS substrate was fabricated by assembling β-cyclodextrin-modified gold nanoparticles (β-CD@AuNPs) on polytetrafluoroethylene (PTFE) film coated with perfluorinated liquid (β-CD@AuNP/PTFE). The concentrations of benzo(a)pyrene (BaP), naphthalene (Nap), and pyrene (Pyr) residues on fruit and vegetable surfaces could be detected at 0.25, 0.5, and 0.25 μg/cm2, respectively, and all the relative standard deviations (RSD) were less than 10%, indicating that the β-CD@AuNP/PTFE exhibited high sensitivity and stability. The lightweight network was then used to construct a classification model for identifying various PAH residues. ShuffleNet obtained the best results with accuracies of 100%, 96.61%, and 97.63% for the training, validation, and prediction datasets, respectively. The proposed method realised the in situ detection and identification of various PAH residues on fruit and vegetables with simplicity, celerity, and sensitivity, demonstrating great potential for the rapid, nondestructive analysis of surface contaminant residues in the food-safety field.

Sulfonated poly(p-phenylene)-based ionomer/PTFE composite membrane with enhanced performance and durability for energy conversion devices

Proton exchange membranes (PEMs) have to be fabricated as thin as possible to minimize the ohmic loss in the cell voltage of proton exchange membrane fuel cells (PEMFCs) and water electrolyzers (PEMWEs). Additionally, the dimensional and mechanical stabilities of the PEMs must be maintained because they are critical for prolonging the cell lifespan in energy conversion devices that are used in moist environments. Herein, a sulfonated poly(p-phenylene)-based (SPP) multiblock ionomer is impregnated into a porous polytetrafluoroethylene (PTFE) substrate as a practical strategy for fabricating a mechanically robust and thin membrane. A five-layered structure is fabricated using two PTFE substrates as the composite membrane to increase the interfacial area between the SPP ionomer and PTFE; PTFE is treated with n-propyl alcohol to mediate the interfacial interactions between the two incompatible components. The composite membrane exhibits enhanced dimensional stability and mechanical properties compared with those of the pristine membrane owing to the SPP ionomer interlocking with PTFE. Regarding the electrochemical properties, the cell performance of the composite membrane displays a high current density of 1.52 A/cm2 at 0.5 V and 7.90 A/cm2 at 1.9 V for PEMFC and PEMWE, respectively; these densities are 32% and 16% greater, respectively, than that of Nafion212.

Thermodynamic and kinetic analyses of Janus membrane scaling in membrane distillation for zero liquid discharge engineering

Scaling phenomena are the principal obstacle to the factual application of membrane distillation (MD). In this study, we fabricated a Janus membrane composed of a commercial polytetrafluoroethylene substrate, a superhydrophobic surface layer, and a hydrophilic reverse side coated by MXene nanosheets via a simple spraying method. The virgin and modified membranes were carried out and compared in zero liquid discharge (ZLD) MD experiments. MD flux analysis showed that all the membranes experienced severe flux decline during the ZLD process. Saturation index, Gibbs free energy and nucleation energy barrier were calculated to explain the observed difference in scaling behavior. Screenage assessment of the homogeneous nucleation and heterogeneous nucleation showed that the severe scaling developed from some small clusters of the new phase, wherein the thermodynamic energy barrier played a critical role in determining the anti-scaling behavior for these unsmooth surfaces. Model analysis and data fitting were used to conclude the kinetic behavior of the virgin and modified membranes in the ZLD engineering. Finally, we evaluated the reversible and irreversible scaling after twice washing. Therefore, this study may provide instructive insights to design novel anti-fouling membranes and promote practical applications such as industrial brine treatment and ZLD engineering.

Nanostructures on Fluoropolymer Nanotextile Prepared Using a High-Energy Excimer Laser.

This study is focused on polytetrafluoroethylene (PTFE) porous nanotextile and its modification with thin, silver sputtered nanolayers, combined with a subsequent modification with an excimer laser. The KrF excimer laser was set to single-shot pulse mode. Subsequently, the physico chemical properties, morphology, surface chemistry, and wettability were determined. Minor effects of the excimer laser on the pristine PTFE substrate were described, but significant changes were observed after the application of the excimer laser to the polytetrafluoroethylene with sputtered silver, where the formation of a silver nanoparticles/PTFE/Ag composite was described, with a wettability similar to that of a superhydrophobic surface. Both scanning electron microscopy and atomic force microscopy revealed the formation of superposed globular structures on the polytetrafluoroethylene lamellar primary structure, which was also confirmed using energy dispersive spectroscopy. The combined changes in the surface morphology, chemistry, and thus wettability induced a significant change in the PTFE's antibacterial properties. Samples coated with silver and further treated with the excimer laser 150 mJ/cm2 inhibited 100% of the bacterial strain E. coli. The motivation of this study was to find a material with flexible and elastic properties and a hydrophobic character, with antibacterial properties that could be enhanced with silver nanoparticles, but hydrophobic properties that would be maintained. These properties can be used in different types of applications, mainly in tissue engineering and the medicinal industry, where water-repellent materials may play important roles. This synergy was achieved via the technique we proposed, and even when the Ag nanostructures were prepared, the high hydrophobicity of the system Ag-polytetrafluorethylene was maintained.

In situ synchrotron X-ray scission of polytetrafluoroethylene chains and elucidation of dry etching

We investigated the mechanism of polytetrafluoroethylene (PTFE) chain scission through in situ hard X-ray photoelectron spectroscopy at room temperature, 200 °C, and 230 °C. The C–C bonds in the main chain and C–F bonds in the side chains were broken, and F desorption from the PTFE surface was observed at room temperature. The formation of CF3 was also observed from the recombination of broken C–C bonds in the main chain and detached F, which were not induced by soft X-rays. In contrast, when the PTFE substrate was irradiated with hard X-rays at 200 °C, the CF3 intensity initially produced by recombination reactions decreased with irradiation time, and the photoelectron spectrum retained the original PTFE spectrum. Under these conditions, the F1s/C1s intensity ratio did not change with the irradiation time; hence, the fragment containing only CF2, the chemical composition of the original PTFE, was desorbed. When the substrate temperature was 230 °C, the CF3 intensity increased in relation to that at 200 °C. This result indicated that the formation of CF3 via recombination reactions of broken molecular chains is enhanced by thermal assistance. These phenomena were considered to be based on the balance between recombination and desorption by photochemical and pyrochemical reactions. These results will lead to a better understanding of the use of X-ray-irradiated fluorine resins and PTFE in potential space-based environments. This study will also promote the improvement of PTFE microfabrication methods and thin-film formation using synchrotron radiation.

Emulsion Assembly of Graphene Oxide/Polymer Composite Membranes.

Graphene oxide/polymer composite water filtration membranes were developed via coalescence of graphene oxide (GO) stabilized Pickering emulsions around a porosity-generating polymer. Triptycene poly(ether ether sulfone)-CH2NH2:HCl polymer interacts with the GO at the water-oil interface, resulting in stable Pickering emulsions. When they are deposited and dried on polytetrafluoroethylene substrate, the emulsions fuse to form a continuous GO/polymer composite membrane. X-ray diffraction and scanning electron microscopy demonstrate that the intersheet spacing and thickness of the membranes increased with increasing polymer concentration, confirming the polymer as the spacer between the GO sheets. The water filtration capability of the composite membranes was tested by removing Rose Bengal from water, mimicking separations of weak black liquor waste. The composite membrane achieved 65% rejection and 2500 g m-2 h-1 bar-1. With high polymer and GO loading, composite membranes give superior rejection and permeance performance when compared with a GO membrane. This methodology for fabrication membranes via GO/polymer Pickering emulsions produces membranes with a homogeneous morphology and robust chemical separation strength.

Microstructured silicon substrates impregnated with bis(2,4,4-trimethylpentyl) phosphinic acid for selective scandium recovery

The recovery of trace amounts of scandium from process tailings represents a challenging yet critical task for the growing demand for sustainable and renewable technologies. As an important step toward addressing the environmental and technical concerns related to current scandium separation approaches, we developed novel extractant-impregnated surfaces (EIS) that held a thin layer of extractant within a micropillar texturized substrate. Compared with traditional solvent extraction, the EIS requires significantly less volume of extractant and no agitation. About 95 % of scandium is separated from the complex feedstock prepared from industrial waste bauxite residue, and the selectivity of scandium is more than 200 times higher than that of aluminum. Adsorption isotherm and kinetic studies are performed, and the experimental data are in good agreement with the Langmuir isotherm model and indicate pseudo-second-order kinetics. Cryo time-of-flight secondary ion mass spectrometry depth profiling is conducted on post-extraction EIS to unveil the scandium ions transport behaviour. Moreover, it is confirmed the EIS scheme and its underlying principles can be applied to sandblasted polytetrafluoroethylene substrates, which proves the potential of using EIS design at larger scales.

Thin, Flexible, and High-Performance Solid-State Polymer Electrolyte Membranes for Li–O2 Batteries

A solid-state lithium–oxygen battery (SSLOB) has become more attractive as a next-generation energy storage device, with the expectation of long-term safe and wide applications with superior energy density. However, the development of a thin and flexible solid-state electrolyte having good interfacial and chemical stability toward lithium metal and/or oxygen has been a big challenge. Accordingly, a solid-state composite electrolyte membrane has been prepared by impregnating polyethylene glycol (PEG) and succinonitrile plastic crystals (SNPCs) along with lithium bromide redox mediator into a porous polytetrafluoroethylene (PTFE) substrate for application in a SSLOB. The prepared thin electrolyte membrane (23 μm) displays a high ionic conductivity of 1.03 mS cm–1, a tensile strength of 46.5 MPa, and elongation at a break of 100% with excellent flexibility. It also exhibits a wide electrochemical stability window (∼4.9 V) and low interfacial resistance of 80 Ω cm2. The SSLOB cell assembled with the synthesized XPEG/SNPC@PTFE electrolyte membrane shows excellent electrochemical stability during 277 cycles, maintaining a 1000 mAh g–1 discharge capacity. The low terminal voltage difference between the charge and discharge processes of these polymer electrolyte membranes (∼0.65 V) compared to those of liquid or other polymer electrolytes (∼1.4 V) is also an advantageous characteristic for their application in high-performance SSLOBs.

Carbon nitride – PVDF photocatalytic membranes for visible-light degradation of venlafaxine as emerging water micropollutant

Metal-free carbon nitride-based membranes were prepared by embedding bulk or exfoliated graphitic carbon nitride (g-C3N4) photocatalysts in a polyvinylidene fluoride (PVDF) matrix. Supported membranes were also fabricated by immobilising these photocatalysts on a polytetrafluoroethylene (PTFE) substrate. The membranes were tested for venlafaxine (VFX) degradation at a feed concentration of 250 µg L−1 under continuous flow mode operation and using a visible-light emitting diode (LED) as energy source. The reduction of the (002) diffraction peak and the increased intensity of the infrared absorption bands confirmed that the exfoliation process decreased the number of aligned g-C3N4 layers, with a more ordered packing of tri-s-triazine units. Additionally, the small particle size (around 745 and 257 nm for bulk and exfoliated g-C3N4, respectively) and the presence of terminal amino groups in the catalysts allowed for homogeneous dispersion in the PVDF matrix. Despite their different surface roughness and cross-sectional microstructure, all the fabricated membranes exhibited similar photocatalytic filtration performance for VFX degradation, resulting in conversions above 95% after 5 h of irradiation (418 nm with an irradiance of 11.2 W m−2) and keeping the VFX concentration in the effluent negligible up to 48 h of continuous operation (mass removal rate of about 6 mg m−2 h−1). In a more complex water matrix (i.e., surface water), the photocatalytic filtration process led to 50% VFX removal (or 3 mg m−2 h−1) at the steady state. Moreover, the permeate flux remained at about 25 L m−2 h−1 throughout the continuous operation, suggesting that fouling did not occur at these conditions.

Construction of low-cost and long-time proton exchange membranes by using slow-release radical scavenger

The bottlenecks of commercial application of proton exchange membranes (PEM) fuel cell are cost and oxidation stability of PEM. Hence, we encapsulate Resveratrol (Res, a kind of reductant) in hydroxypropyl-β-cyclodextrins (CDs) to prepare the inclusion complexes of Res and CDs (Res@CDs) under the guidance of theoretical arithmetic. Then the Res@CDs are evenly dispersed in Nafion emulsion, which is subsequently combined with porous polytetrafluoroethylene (PTFE) substrate by emulsion pouring method to form the antioxidative composite membrane (Res@CDs-Nafion/PTFE). The as-prepared Res@CDs-Nafion/PTFE shows the similar performance on proton conductivity (103.9 mS cm−1) and hydrogen-air fuel cell (317.84 mW cm−2) compared to the Nafion/PTFE composite membrane. The content of Nafion in the Res@CDs-Nafion/PTFE is less than 30%, which dramatically reduces the production cost compared to pure Nafion membrane. The weight loss of Res@CDs-Nafion/PTFE and Nafion/PTFE immersed in Fenton's reagent after 36 h is 4.97% and 16.49%, respectively, which demonstrate that Res@CDs can enhance oxidation stability of composite membrane. The Res@CDs-Nafion/PTFE offer huge merits of low cost and enhanced oxidation stability, which greatly promotes the application process of long-lifetime PEM fuel cell.

Characterization and Growth of TiO2/ZnO on PTFE Substrates at Different Volumetric Ratios Using Chemical Bath Deposition

Developing non-toxic, semiconductor-doped heterojunction materials for optoelectronic applications on the surface of a flexible substrate is a viable strategy for meeting the world’s energy needs without introducing any environmental issues. In this paper, Ti:TiO2/ZnO nanocomposites were prepared by heat treatment and utilized as an active layer in UV photodetectors. First, a ZnO seed layer was deposited by radio frequency (RF) sputtering on polytetrafluoroethylene (PTFE) substrates. Then, TiO2/ZnO thin films (TFs) were successfully grown by combining volumetric mixtures of TiO2 and ZnO at the ratios of 1:7, 1:3, 3:5, and 1:1 via the chemical bath deposition (CBD) method. The morphological, elemental, and topographical analyses of the grown TFs were investigated through SESEM, EDX, and AFM spectroscopy, respectively. XRD patterns illustrated the presence of the unified (002) peak of the Ti/ZnO hexagonal wurtzite structure in all prepared samples, with intensities indicating a very strong preferential crystallinity with increasing TiO2 ratios. Enhanced diffuse reflectance curves were obtained by UV–Vis spectroscopy, with allowed indirect energy bandgaps ranging from 3.17 eV to 3.23 eV. FTIR characterization revealed wider phonon vibration ranges indicating the presence of Ti–O and Zn–O bonds. Metal–semiconductor–metal (MSM) UV photodetectors were fabricated by thermally evaporating Ag electrodes on the grown nanocomposites. The volumetric ratio of TiO2/ZnO impacted the photodetector performance, where the responsivity, photosensitivity, gain, detectivity, rise time, and decay time of 0.495 AW−1, 247.14%, 3.47, 3.68 × 108 jones, 0.63 s, and 0.99 s, respectively, were recorded at a ratio of 1:1 (TiO2:ZnO). Based on the results, the heterostructure nanocomposites grown on PTFE substrates are believed to be highly promising TF for flexible electronics.

Tuning the diameter and optical properties of ZnO nanorods grown onto flexible substrates at different temperatures

In this study, ZnO nanorods (NRs) have been successfully grown onto polytetrafluoroethylene (PTFE) substrates at low temperatures (85, 90, 95, 100 °C) by chemical bath deposition. Growth temperature for the prepared ZnO NRs was controlled by using electrical oven equipped with digital heat control. It is found that at 95 °C, well vertically aligned ZnO NRs are obtained with enhanced structural and optical properties. The crystallite size, lattice strain, and near-band edge emission of ZnO NRs band gap energy have been significantly improved as confirmed by X-ray diffraction and photoluminescence measurements. The crystallite size increases significantly from 52 to 94 nm as the growth temperature is raised by 10 °C only, i.e., from 85 to 95 °C. Besides, the near band edge emission to deep level emission ratio has been also enhanced, from 1.328 to 4.474 for 85 to 95 °C, respectively. The obtained results highlight that the properties of ZnO NRs can be tuned and controlled through the growth temperature. Besides, this study introduced a facile cost-effective method to produce ZnO NRs for flexible based-electronic applications.

Antibacterial Thin Films Deposited from Propane-Butane Mixture in Atmospheric Pressure Discharge.

Antibacterial coatings on biomedical instruments are of great interest because they can suppress bacterial colonization on these instruments. In this study, antibacterial polymeric thin coatings were deposited on teflon substrates using atmospheric pressure plasma polymerization from a propane-butane mixture. The plasma polymerization was performed by means of surface dielectric barrier discharge burning in nitrogen at atmospheric pressure. The chemical composition of plasma polymerized propane-butane films was studied by energy-dispersive X-ray spectroscopy (EDX) and FTIR. The film surface properties were studied by SEM and by surface energy measurement. The EDX analysis showed that the films consisted of carbon, nitrogen and oxygen from ambient air. The FTIR analysis confirmed, in particular, the presence of alkyl, nitrile, acetylene, imide and amine groups. The deposited films were hydrophilic with a water contact angle in the range of 13-23°. The thin film deposited samples were highly active against both S. aureus and E. coli strains in general. On the other hand, the films were cytocompatible, reaching more than 80% of the cell viability threshold compared to reference polystyrene tissue.

Dyeable Hydrophilic Surface Modification for PTFE Substrates by Surface Fluorination.

Polytetrafluoroethylene (PTFE) is the most widely used fluoropolymer that has various functionalities such as heat resistance, chemical resistance, abrasion resistance, and non-adhesiveness. However, PTFE is difficult to dye because of its high water repellency. In this study, the PTFE surface was modified by a combination of gold sputtering and surface fluorination to improve dyeability. X-ray photoelectron spectroscopy indicated that, compared with the untreated sample, the gold-sputtered and acid-washed surface of PTFE had a negligible number of C-F terminals. Furthermore, the intensity of the C-C peak increased drastically. The polar groups (C=O and C-Fx) increased after surface fluorination, which enhanced the electronegativity of the surface according to the zeta potential results. Dyeing tests with methylene blue basic dye showed that the dye staining intensity on the surface of fluorinated PTFE samples was superior to other samples. It is due to the increased surface roughness and the negatively charged surface of fluorinated PTFE samples. The modified PTFE substrates may find broad applicability for dyeing, hydrophilic membrane filters, and other adsorption needs.

Effects of surface oxide layer on the impact dynamic behavior of molten aluminum droplets

Oxide layer is easily formed on the surface of some metal droplets, which affects the dynamic behavior of droplet impact. In this paper, experiments were conducted for the impacting process of a molten aluminum droplet on a Teflon substrate. The thickness of surface oxide layer of aluminum droplets was controlled by varying oxygen concentrations in the gas atmosphere. The effects of oxygen concentration and Weber number on droplet spread, rebound, and splash behavior were investigated. The results show that the oxygen concentration in the environment directly affects the droplet impact behavior. The differences in the droplet retraction process at different oxygen concentrations are more significant than the spread process. Strong retraction causes droplet rebound (We = 17.11) and splash (We = 102.3) in hypoxic environments, whereas only weak retraction in air. The viscous dissipation of the droplet impact in different oxygen concentration environment is estimated by counting the droplet bounce height, and the dissipation increases with the increase in the oxygen concentration. The thickness of the oxide layer measured by scanning electron microscope became thinner as the oxygen concentration decreases and, accordingly, the aluminum droplet collisions show different dynamic behavior. The experimental results are analyzed and explained regarding the reduction in surface tension, the increase in viscous forces, and the shear-thinning properties which increase the viscous dissipation during retraction. Ryan model was used to predict the droplet maximum spreading factor ξmax with the Weber number to the power of 0.5, better than the energy conservation-based Pasandideh-Fard model.

국내 수송환경에 적합한 마찰전기 나노발전기의 발전특성 분석

Sustainable energy supplies without the recharging and replacement of charge storage device have become increasingly important. Among various energy harvesters, the triboelectric nanogenerator (TENG) has attracted considerable attention due to its high instantaneous output power, broad selection of available materials, eco-friendly and inexpensive fabrication process, and various working modes customized for target applications. The TENG harvests electrical energy from wasted mechanical energy in the ambient environment. TENG devices are very likely to be used in next-generation renewable energy and energy harvesting. TENG devices have the advantage of being able to manufacture very simple power devices. In this experiment, various organic dielectrics and inorganic dielectrics were used to improve the open voltage of TENG, Among the various organic dielectrics, Teflon-based FEP, which has the highest electron affinity, showed the highest open voltage and Al electrode was fabricated on Teflon substrate by sputtering deposition process. And AAO (Anodized Aluminum Oxide) nanostructures were applied to maximize the specific surface area of the TENG device. The power generation of TENG within the acceleration level (0.25, 0.5, 1.0, 1.5 and 2 G) and the frequency range (5-120 Hz) of the domestic transport environment was up to 4 V.

Ultrafast organic solvent nanofiltration in C[sbnd]C bonded conjugated microporous membrane-based nanochannels by space-confined polymerization

Organic solvent nanofiltration is a new membrane technology for separation of organic solvents with low energy consumption and environmental compatibility. However, commercial ultrafiltration membranes are unsuitable for organic solvents separation owing to their low retention and poor solvent resistance. CC bonded conjugated microporous polymer (CCMP) membranes consisting of all-rigid conjugated systems feature well-developed microporosity and excellent organic resistance. Herein, we report a strategy to prepare solvent-resistant CCMP@PTFE composite membrane by portioning channels in polytetrafluoroethylene (PTFE) ultrafiltration membrane by space-confined polymerization. Owing to intrinsic micropores from crosslinking of multifunctional rigid building units and the robustness of PTFE substrate, three CCMP@PTFE membranes exhibit outstanding separation performance, solvent resistance and high flexibility, which rival against the best of those reported membranes. This strategy inspires the design of OSN membranes with high performance.

Polytetrafluoroethylene-based gas diffusion electrode for electrochemical generation of hydrogen peroxide

Hydrogen peroxide (H2O2) is a versatile oxidizing agent with numerous applications in various industries. One application of H2O2 is for water treatment, where it is combined with an ultraviolet (UV) radiation source to produce hydroxyl radicals. For point-of-use water treatment devices, the in-situ electrochemical generation of H2O2 is a more attractive solution compared with the external addition of chemicals. One common electrode for H2O2 production is gas diffusion electrode (GDE), which facilitates oxygen transport to the reaction zone. In our study, a GDE was developed based on an expanded polytetrafluoroethylene (ePTFE) substrate for the in-situ cathodic production of H2O2. The GDE characterization indicated its longevity and tolerance to a pressure difference of more than 70 psi, which is typical in residential water distribution systems. The performance of the GDE was evaluated in an electrochemical cell based on various parameters. The cell generated ∼0.6 mM H2O2 at a catalyst loading of 0.22 mg cm–2, flow rate of 40 mL min–1, and current density of ∼200 A m–2. When coupled with a UV-LED array, the ePTFE-based cell was able to oxidize >60% of methylene blue. To the best of our knowledge, this is the first study in which an ePTFE-based GDE has been applied to the electrochemical generation of H2O2, with the ePTFE network as the gas diffusion layer (GDL), thus making the system practically leak-free. The air-breathing electrochemical cell with the ePTFE-based GDE is a reliable means of generating H2O2.