Nafion Composite Membranes Research Articles

Effects on the electrochemical performance of surface-modified mordenite in a PTFE Nafion composite membrane for direct methanol fuel cells

Mordenite (MOR)/PTFE Nafion composite membranes were produced by impregnating Nafion solutions in a PTFE porous support with a modified form of MOR. A 3-mercaptopropyl triethoxysilane (MPTES) - MOR mixture is used as a filler in the PTFE Nafion membrane to block methanol crossover and increase water uptake. An experiment was conducted with a membrane without M-MOR (PTFE Nafion membrane) and a membrane with M-MOR at 2, 4, and 10 wt% (2-, 4-, and 10-M-MOR/PTFE Nafion membranes, respectively). In order to improve the interfacial properties, surface modification of the zeolite was conducted with a silane coupling reaction. The MOR samples were analyzed by SEM, SEM-EDS, and BET surface area analysis. The Nafion membrane was analyzed by SEM, according to the water uptake, and by an electrochemical analysis. The 10-M-MOR/PTFE Nafion membrane showed greater water uptake of 75% compared to the PTFE Nafion membrane without M-MOR (28%). It was found that the addition of MOR had a positive effect on the reduction of the methanol permeability of the MOR/PTFE Nafion membrane. The DMFC (Direct Methanol Fuel Cell) power density of MEA with the 4-M-MOR/PTFE Nafion membrane (4-M-MOR MEA) was found to be 71% higher than that of the PTFE Nafion membrane (0-M-MOR MEA).

Graphene Oxide-Intercalated Microbial Montmorillonite to Moderate the Dependence of Nafion-Based PEMFCs in High-Humidity Environments

The most fatal disadvantage of Nafion-based proton-exchange membrane fuel cells (PEMFCs) is their significant performance losses at low relative humidities (RH ≤ 80%), making external humidification necessary. In this work, a graphene oxide (GO)-intercalated microbial montmorillonite (mMMT) layered stack (GO@mMMT) was prepared to enhance the proton conductivity of a Nafion membrane under a low humidity at elevated temperatures. The prepared mMMT had a high specific surface area and pore volume due to microbial mineralization, allowing GO to act as a spacer intercalated between MMT layers. This layered stack greatly enhanced the water absorbance and retention capacity of GO@mMMT/Nafion composite membranes. The GO@mMMT/Nafion composite membrane exhibited excellent proton conductivity under various humidities. Particularly, the 0.5GO@mMMT/Nafion sample achieved a proton conductivity of 36.4 mS·cm–1 at 80 °C/98% RH and 17.3 mS·cm–1 at 80 °C/20% RH, which was 82% and 188% higher than that of the recast Nafion membrane, respectively. The assembled single cell reached a peak power density of 546 mW·cm–2, which was 60% higher than that of the recast Nafion single cell. These results indicate that the Nafion composite membranes with GO@mMMT incorporated layered stacks show substantial potential for PEMFC applications with simplified water management.

High rate lithium slurry flow batteries enabled by an ionic exchange Nafion composite membrane incorporated with LLZTO fillers

Lithium slurry flow batteries (LSFBs) possessing decoupled energy/power density feature and high energy density are considered as the most promising next-generation energy storage devices. However, their cycling stability is depressed by the high permeability of active components through porous separator and low conductivity of lithium ion in non-porous membrane. Herein, a novel Nafion/PVDF/LLZTO ion exchange membrane (IEM) with high ion conductivity and mechanical properties is proposed. As-optimized IEM possesses an ionic conductivity of 0.29 mS cm−1. Both experimental and density functional theory (DFT) calculation studies suggest that the complementary effect between inorganic ceramic fillers LLZTO and polymer materials favor the generation of new Li+ migration expressway and dehydrofluorination. The H-bonding interactions can successfully address the poor mechanical strength issues. Moreover, the sandwich-like structure by commercialized PE buffer layer will be beneficial to the improved stability and can effectively suppress the swelling effect of membrane in organic electrolyte. Consequently, LFP//LTO slurry cells containing PE/NPL3/PE membrane exhibit extraordinary performance under 0.3 C. Assembled slurry pouch cells could be cycled stably for more than 270 h at room temperature. This ingenious strategy of introducing inorganic ceramic fillers into the composite membrane will pave a novel promising direction to the development of LSFBs.

Nafion Composite Membrane Reinforced By Phosphonated Polypentafluorostyrene Nanofibers

The membrane is one of the crucial components of fuel cells. Applying composite membranes for fuel cells is a promising option due to better mechanical properties compared to membranes without reinforcement. Composite membranes can be prepared by combining ionomer with a filler which can be selected from many types of materials, such as polymers, ceramics, carbons, and metals. Filler materials exist in different nanostructures which provide flexible designs for composite membranes. However, the main issue in composite membranes is a trade-off among properties when adjusting the ratio between ionomer and filler, especially between ionic conductivity and mechanical modulus. On the one hand, maintaining high protonic conductivity is possible when small concentrations of reinforcing fillers are incorporated. On the other hand, a high amount of reinforcement can improve the mechanical properties significantly but could result in low protonic conductivity as well. Our strategy to overcome this issue is by employing protonic conductive nanofibers as reinforcement. Electrospinning is a versatile method to transform polymer solutions into long and solid nanofibers. Electrospun fibermats possess a high porosity and contain voids which can be filled with an ionomer like Nafion by spraycoating to form a dense composite membrane.We were successful in producing electrospun nanofibers from phosphonated polypentafluorostyrene (PWN70) and unmodified polypentafluorostyrene (PPFSt). PWN70/Nafion and PPFSt/Nafion composite membranes were prepared separately by spraycoating of a Nafion solution into PWN70 and PPFSt fibermats that have comparable thickness and fiber loading. From tensile tests, we found that composite membranes made from PWN70/Nafion and PPFSt/Nafion have much higher Youngs’ modulus (E) than pure Nafion (Figure 1A). Although PWN70/Nafion is a relatively brittle membrane, it has the best Youngs’ modulus and yield stress. Protonic conductivity is also a crucial membrane property which can be determined by electrochemical impedance spectroscopy. In Figure 1B, Nafion reinforced by PPFSt fibers has a reduced conductivity due to non-ion-conductive PPFSt. Surprisingly, the protonic conductivity of a PWN70/Nafion composite membrane is similar to spraycoated Nafion. Without reducing much the protonic conductivity, the PWN70/Nafion composite membrane shows comparable ohmic resistance to the spraycoated D2020 in fuel cell operation which has also been done in this work. Since the PWN70 nanofibers are ion-conductive and electro-spinnable, the nanofibers offer benefits when designing fiber-reinforced composite membrane possessing both good mechanical stability and protonic conductivity. Figure 1

Electrochemical Analysis of Polymer Membrane with Inorganic Nanoparticles for High-Temperature PEM Fuel Cells

In order to solve the challenge that battery performance rapidly deteriorates at a high temperature condition of 100 °C or higher, ZrO2-TiO2 (ZT) with various Zr:Ti ratios synthesized by a sol-gel method were impregnated in a Nafion membrane. Through material characterization, a unique ZT crystal phase peak with a Zr-O-Ti bond was identified, and the band range associated with this bond and intrinsic functional group region could be identified. These prepared powders were blended with 10% (w/w) Nafion-water dispersion to prepare composite Nafion membranes (NZTs). The water uptake increased and the ion exchange capacity decreased as the TiO2 content increased in the NZTs in which particles were uniformly distributed. These results were superior to those of the conventional Nafion 112. The electrochemical properties of all membranes was measured using a polarization curve in a single cell with a reaction area of 9 cm2, and the operating conditions in humidified H2/air was 120 °C under 50% relative humidity (RH) and 2 atm. The composite membrane cell with nanoparticles of a Zr:Ti ratio of 1:3 (NZT13) exhibited the best electrochemical characteristics. These results can be explained by the improved physicochemical properties of NZT13, such as optimized water content and ion exchange capacity, strong intermolecular forces acting between water and nanofillers (δ), and increased tortuosity by the fillers (τ). The results of this study show that the NZT membrane can replace a conventional membrane under high-temperature and low-humidity conditions. To examine the effect of the content of the inorganic nanomaterials in the composite membrane, a composite membrane (NZT-20, NZT-30) having an inorganic nano-filler content of 20 or 30% (w/w) was also prepared. The performance was high in the order of NZT13, NZT-20, and NZT-30. This shows that not only the operating conditions but also the particle content can significantly affect the performance.

Comparative Studies on the Proton Conductivities of Hafnium-Based Metal-Organic Frameworks and Related Chitosan or Nafion Composite Membranes.

Hafnium (Hf)-based UiO-66 series metal-organic frameworks (MOFs) have been widely studied on gas storage, gas separation, reduction reaction, and other aspects since they were first prepared in 2012, but there are few studies on proton conductivity. In this work, one Hf-based MOF, Hf-UiO-66-fum showing UiO-66 structure, also known as MOF-801-Hf, was synthesized at room temperature using cheap fumaric acid as the bridging ligand, and then imidazole units were successfully introduced into MOF-801-Hf to obatin a doped product, Im@MOF-801-Hf. Note that both MOF-801-Hf and Im@MOF-801-Hf demonstrate excellent thermal, water, and acid-base stabilities. Expectedly, the maximum proton conductivity (σ) of Im@MOF-801-Hf (1.46 × 10-2 S·cm-1) is nearly 4 times greater than that of MOF-801-Hf (3.98 × 10-3 S·cm-1) under 100 °C and 98% relative humidity (RH). To explore their possible practical application value, we doped them into chitosan (CS) or Nafion membranes as fillers, namely, CS/MOF-801-Hf-X, CS/Im@MOF-801-Hf-Y, and Nafion/MOF-801-Hf-Z (X, Y, and Z are the doping percentages of MOF in the membrane, respectively). Intriguingly, it was found that CS/MOF-801-Hf-6 and CS/Im@MOF-801-Hf-4 indicated the highest σ values of 1.73 × 10-2 and 2.14 × 10-2 S·cm-1, respectively, under 100 °C and 98% RH and Nafion/MOF-801-Hf-9 also revealed a high σ value of 4.87 × 10-2 S·cm-1 under 80 °C and 98% RH, which showed varying degrees of enhancement compared to the original MOFs or pure CS and Nafion membranes. Our study illustrates that these Hf-based MOFs and related composite membranes offer great potential in electrochemical fields.

Structurally modulated and functionalized carbon nanotubes as potential filler for Nafion matrix toward improved power output and durability in proton exchange membrane fuel cells operating at reduced relative humidity

Development of a high-performance and durable proton exchange membrane (PEM) for low relative humidity (RH) operation is imperative for further commercialization of hydrogen-air fuel cell (HAFC). In this work, we reported the synthesize of carbon nanotubes-unzipped carbon nanotubes (CNTs-UCNTs) hybrid via calcination process with ammonium fluoride. Further, the 4-benzenediazonium sulfonate was used to sulfonate both CNTs and UCNTs to form sulfonated CNTs-sulfonated UCNTs (SCNTs-SUCNTs) hybrid. The unzipping enlarged the surface area of CNTs-UCNTs hybrid and facilitated the accommodation of a large density of sulfonic acid (-SO 3 H) groups during sulfonation. Thus, SCNTs-SUCNTs hybrid incorporation with the host Nafion matrix results a uniform composite membrane with high density of –SO 3 H groups per unit volume. It positively impacts thermal, mechanical and oxidative stabilities, and physicochemical performances of composite membrane. Besides, Nafion/SCNTs-SUCNTs composite membrane afforded credible proton conductivity, current output, power output, and durability, which are 0.015 S cm −1 , 1.000 A cm −2 , 0.343 W cm −2 , and 0.15 mV h −1 , respectively when operating the HAFC at 60 °C under 20% RH. In contrast, bare Nafion, Nafion/CNTs, and Nafion-212 membranes exhibited inferior proton conductivity, current output, power output, and durability under identical HAFC operating conditions. Efficient proton transport ability of Nafion composite membrane given by SCNTs-SUCNTs hybrid is beneficial for HAFC operation under low relative humidity. • Sulfonation of UCNTs beneficial to Nafion composite membrane to improve physiochemical and thermomechanical properties. • Nafion/SCNTs-SUCNTs showed enhanced proton conductivity compared to pristine Nafion and Nafion-212 membranes under low RH. • The power density and durability of Nafion/SCNTs-SUCNTs membrane are few folds better than pristine Nafion.

Nafion Composite Membranes Impregnated with Polydopamine and Poly(Sulfonated Dopamine) for High-Performance Proton Exchange Membranes.

We prepared Nafion composite membranes by impregnating Nafion-212 with polydopamine, poly(sulfonated dopamine), and poly(dopamine-co-sulfonated dopamine) using the swelling–filling method to generate nanopores in the Nafion framework that were filled with these polymers. Compared to the pristine Nafion-212 membrane, these composite membranes showed improved thermal and mechanical stabilities due to the strong interactions between the catecholamine of the polydopamine derivatives and the Nafion matrix. For the composite membrane filled with poly(sulfonated dopamine) (N-PSDA), further interactions were induced between the Nafion and the sulfonic acid side chain, resulting in enhanced water uptake and ion conductivity. In addition, filling the nanopores in the Nafion matrix with polymer fillers containing aromatic hydrocarbon-based dopamine units led to an increase in the degree of crystallinity and resulted in a significant decrease in the hydrogen permeability of the composite membranes compared to Nafion-212. Hydrogen crossovers 26.8% lower than Nafion-212 at 95% relative humidity (RH) (fuel cell operating conditions) and 27.3% lower at 100% RH (water electrolysis operating conditions) were obtained. When applied to proton exchange membrane-based fuel cells, N-PSDA exhibited a peak power density of 966 mW cm–2, whereas N-PSDA showed a current density of 4785 mA cm–2, which is 12.4% higher than Nafion-212 at 2.0 V and 80 °C.

High-performance fuel cells using Nafion composite membranes with alignment of sulfonated graphene oxides induced by a strong magnetic field

Proton exchange membrane (PEM) is a key component of proton exchange membrane fuel cells (PEMFCs) and provides proton conduction between fuel and oxidant, and it is vitally important and practical to develop PEMs with high proton conductivity through membranes. However, it is still a major challenge to develop such membranes with high through-plane proton conductivity. In this study, Nafion composite membranes with sulfonated graphene oxides (SGOs) were prepared from self-assembly sol-gel either in or not in a strong magnetic field. Microstructures, water uptake, and proton conductivity of the SGO/Nafion composite membranes have been investigated extensively. For the SGO/Nafion composite membranes recast without a magnetic field, it is found that the water uptake and in-plane proton conductivity are greatly increased with the increasing SGO content. Interestingly, SGO/Nafion composite membranes with a low SGO content of ∼ 0.5 wt% exhibit lower crystallinity and higher in-plane proton conductivity. For the SGO/Nafion composite membranes recast in a strong through-plane magnetic field, it is very appealing to find their through-plane proton conductivity is significantly higher than that of the composite membranes recast without a magnetic field. This is attributed to that the protons transport in the membranes preferentially along the water channels primarily interconnected by the aligned SGOs through-plane induced by the strong magnetic field, as confirmed by SEM. Applied in a single PEMFC, the resultant SGO/Nafion composite membrane with 1 wt% SGOs, recast in a strong magnetic field of 1.5 T, demonstrates a high power-density of 1.056 W cm-2, which is far superior to those of pristine Nafion and SGO/Nafion composite membranes recast without a magnetic field. The study provides a novel strategy for preparing proton exchanging membranes with high performances for new-generation fuel cells.

Highly Durable Membrane Electrode Assembly with Multiwalled Carbon Nanotubes/CeO2‐Reinforced Nafion Composite Membrane by Spraying Method for Fuel Cell Applications

AbstractFor achieving economically viable polymer electrolyte membrane fuel cells (PEMFCs) in the commercial market, simplifying the fabrication process and manufacturing of robust membrane electrode assembly (MEA) are important. Herein, a single spray‐coating method for developing a robust and free‐standing reinforced Nafion composite membrane and electrodes is reported. By comparing the fabricated membrane's morphology under diverse process conditions including the nozzle‐to‐substrate distance and solution‐loading rates, the optimized spray‐coating for uniformly deposited spray‐based membrane without any defects has been determined. To explain this optimized condition, a simple theoretical model based on the concept of the surface coverage of sprayed droplets is proposed. The fabricated multiwalled carbon nanotubes/CeO2‐reinforced Nafion composite membrane shows excellent mechanical properties with minimal proton‐conducting loss despite using additional fillers of total 4 wt% in the Nafion matrix. By successively depositing the catalyst layer on that membrane using the same spray‐coating device, an MEA with the reinforced spray‐based membrane has been successfully fabricated; moreover, diverse electrochemical measurements and durability tests have been conducted. The MEA with the reinforced membrane shows comparable initial performance and considerably higher performance after the durability test compared to the MEA with commercial Nafion membrane.

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.

Sandwich‐like Nafion composite membrane with ultrathin ceria barriers for durable fuel cells

Improving the durability of the membrane electrode assembly (MEA) while obtaining high performance is required to further commercialize polymer electrolyte membrane fuel cells (PEMFCs). The durability of PEMFCs is improved by incorporating radical scavengers, such as CeO2 (ceria), into the MEA, especially the membrane. However, nanosized ceria particles are generally mixed with ionomers and are cast on substrates to fabricate composite membranes. In such a case, controlling their morphology and avoiding particle agglomeration is difficult. Herein, we report a novel method for constructing a robust membrane by incorporating ultrathin ceria barriers into the outermost sides of a commercial Nafion membrane to effectively alleviate radical attacks while ensuring the high uniformity and controllability of ceria layers. The improved durability of the composite membrane is confirmed via ex situ Fenton's test and in situ operation of a fuel cell. Moreover, we observe that the amount of fluoride ion emission and the loss of proton conductivity of the membranes decrease as the CeO2 density increases. The MEA comprises a modified membrane with CeO2 barriers that show proper areal density. It demonstrates excellent durability under accelerated environmental conditions (open circuit voltage test) and acceptable initial performance with an insignificant decrease in proton conductivity.

Polyamide-coated Nafion composite membranes with reduced hydrogen crossover produced via interfacial polymerization

Nafion, a perfluoro-sulfonic acid (PFSA)-based polymer, is a promising material that will help realize the commercialization of proton exchange membrane-based fuel cells (PEMFCs) and proton exchange membrane water electrolyzers (PEMWEs). However, Nafion also exhibits reduced mechanical and dimensional stability and increased hydrogen crossover under cell operating conditions in real operational settings, that is, in a hydrated state or in water at 60–80 °C. These factors may negatively affect cell efficiency and durability and thus must be addressed. To overcome these limitations, polyamide-coated Nafion composite membranes were developed for the first time via interfacial polymerization. 3,5-Diaminobenzoic acid (DABA), which contains carboxyl functional groups, was used as a monomer to add hydrophilicity to the membrane, and the coating layer thickness was controlled by adjusting the DABA content. A nanoscale polyamide (PA) layer was coated on the surface of Nafion-212 to fabricate a membrane, PA-c3-Nafion. PA-c3-Nafion was found to show ion conductivity 13.6% higher than that of a pristine Nafion-212 membrane at 80 °C, while providing improved mechanical performance and dimensional stability. In particular, at 95% RH, the hydrogen permeability of PA-c3-Nafion was 16.4% lower than that of Nafion-212 while, in a fully hydrated state, the hydrogen permeability of PA-c3-Nafion was 21.2% lower than that of Nafion-212. The LSV test results also showed that the degree of hydrogen crossover was significantly lower in PA-c3-Nafion than in Nafion-212.

High‐temperature operation of PEMFC using pore‐filling PTFE /Nafion composite membrane treated with electric field

A pore-filling polytetrafluoroethylene (PTFE)/Nafion composite membrane was developed for the high-temperature operation of proton-exchange membrane fuel cell (PEMFC). Porous PTFE substrate was filled with Nafion solution and cast under an electric field to align ion channel in the through-plane direction, in which thermal stability and proton conductivity were improved simultaneously. The membranes keep their ion-exchange ability at high temperatures above 110°C, whereas the casting membranes do not. Enhanced proton conductivity of 158 mS cm−2 at 80°C was observed in the developed membrane; the conductivity is maintained up to 130°C. The operation of PEMFC with the electrically treated membrane at 120°C showed a performance improvement of 40% compare to the non-treated pore-filling membrane as indicated by enhanced proton conductivity. In this study, we demonstrate that the electrical alignment of the ion channel in the through-plane direction improves the proton conductivity and fuel cell performance at a high temperature for a pore-filling composite membrane.

Electrospun multi-scale nanofiber network: hierarchical proton-conducting channels in Nafion composite proton exchange membranes

Electrospun multi-scale nanofiber network: hierarchical proton-conducting channels in Nafion composite proton exchange membranes

Magnetic aligned sulfonated carbon nanotube/Nafion composite membranes with anisotropic mechanical and proton conductive properties

Nafion composite membranes with various amounts of sulfonated multi-walled carbon nanotubes (Su-CNTs) were prepared either in or without a strong magnetic field. Interestingly, it is found that being recast in a strong magnetic field, the tensile strength at break and proton conductivity of Su-CNTs/Nafion composite membranes parallel to the magnetic field direction were higher than those perpendicular to magnetic field. Remarkably, such anisotropic mechanical property and proton conductivity of Su-CNTs/Nafion composite membranes strongly depend on water uptake and temperature, in particular the content of Su-CNTs. Quite a different dependence of the proton conductivity of the composite membranes on Su-CNT content, relative humidities and temperatures is well explained for the anisotropic proton conductivity of the Su-CNTs/Nafion membrane recast in a strong magnetic field, which is attributed to the preferential proton transporting along ionic water channels mainly coalesced by the orientated Su-CNTs at a specific water uptake. For Nafion composite membranes with 5 wt.% Su-CNTs, the proton conductivity along the direction of treating magnetic field approaches to 0.216 S/cm, which is $$\sim$$ 46% higher than that perpendicular to the magnetic field at 95 $$^{\circ }$$ C. The present work provides a deep insight of the humidity and temperature dependence of proton conductivity of Su-CNTs/Nafion composite membranes and a new strategy for fabrication proton exchange membranes with high proton conductivity as well as good mechanical property.

Single-crystal-to-single-crystal transformations among three Mn-MOFs containing different water molecules induced by reaction time: crystal structures and proton conductivities.

Three Mn-MOFs {[Mn3(μ4-L)2(H2O)7]·4H2O}n (1), {[Mn3(μ5-L)2(H2O)6]·4H2O}n (2) and {[Mn3(μ7-L)2(H2O)2]}n (3) (H3L = 5-(6-carboxypyridin-3-yl)isophthalic acid) were obtained under different reaction times and temperatures. Interestingly, induced by reaction time, compound 1 can lose one water molecule and SC-SC transform into compound 2. Similarly, compound 2 can also SC-SC transform into 3. Studies on two SC-SC transformation processes were carried out and the transformation mechanisms were deduced, which were verified by TG analyses. Different numbers of water molecules in the three compounds resulted in different coordination environments of the metal cation, coordination modes of the L3- ligand, continuities of hydrogen bonds, dimensions of framework and porosities. The AC impendence spectra studies revealed that compounds 1-3 can enhance the proton conductivities of the Nafion composite membrane to about 47.77%, 36.88% and 21.28%, respectively. It is speculated that the highest proton conductivity of compound 1 may be due to its continuous hydrogen bond chain and highest water uptake, which were mainly decided by the number of water molecules.

Two acidic coordination polymers containing uncoordinated carboxyl groups: Syntheses, crystal structures and proton conductivities in Nafion composite membranes

Two coordination polymers [Cu(H2L)(bpyBr)]n (1) and [Ni(H2L)(bpy)(H2O)2]n (2) (H4L ​= ​5,5’-(butane-1,4-diylbis (oxy)) diisophthalic acid, bpyBr ​= ​4,4′-dibromo −2, 2′-bipyridyl, bpy ​= ​4, 4′-bipyridyl) were synthesized at lower temperature and weaker acidity condition. Crystal structure studies revealed that both compounds exhibited 2-D coordination layer with uncoordinated protonated –COOH groups, which can promote the acidity of compounds, form hydrogen bonds and benefit to proton conducting behavior. So, their proton conductivities have been evaluated through incorporating with Nafion to form composite membrane. AC impedance spectra studies suggested that compounds 1–2 can promote the proton conductivity of the composite membrane about 15.97% and 24.61% higher than that of pure Nafion membrane, respectively. The higher proton conductivity of 2/Nafion should be attributed to the continuous hydrogen bonding chains in the crystal structure.

Fabrication and characterization of a novel Nafion‐PTFE composite hollow fiber membrane

AbstractNafion has been widely used in electrochemistry, but there are only a few reports on its application in other fields, such as, gas separation, even though it exhibits good performance. The primary reason for that is the high cost of Nafion and making a composite membrane with a thin Nafion layer is a potential solution to solve this problem. In this study, a novel Nafion‐PTFE composite hollow fiber membrane, which had a thin (~5 μm) and detect‐free Nafion layer on PTFE surface, without Nafion filling substrate pores was developed, differing from the reported ones in which Nafion resin was required to impregnate into porous PTFE membrane as thorough as possible to ensure the ion conductivity and operation stability. The surface morphology, crystallite, solubility in ethanol/water mixture, and water uptake of membranes were systemically investigated. The gas permeance tests were also conducted. The permeances of different gasses of prepared composite membranes were significantly enhanced compared with the commercial membranes due to the decrease of Nafion thicknesses, while the selectivity remained the same, verifying the detect‐free structure of Nafion layer on PTFE substrate. This study provided a good reference for the preparation and application of low‐cost Nafion composite membranes.

Electromechanical properties of Nafion/carbon nanotube composites enhanced by black phosphorus

ABSTRACT Ionic polymer-Carbon nanotube composite (IPCC) actuators based on black phosphorus (BP)-Nafion composite membranes were fabricated. BP-Nafion composite was used as the ionic matrix with functional carbon nanotube as electrodes. BP presents as a promising material owing to its high charge mobility using in energy storage materials. It was used in Nafion composite improving the electromechanical properties of BP-Nafion composite. Significantly the interaction between BP and lithium ion was strong which restricted the back diffusion of cation during action and thus enhanced the deformation of actuator without back-relaxation. In addition, layer crystal structure of BP protected the inter-lamellar liquid from evaporation thus ensured the durability. The result IPCC actuator exhibited improvement actuation with blocking force of 2 wt.% BP-Nafion composite of 33.6 gf g−1 for 30s under an electrical field of 2 V, 2.7 times that of neat Nafion. Actuation behavior under AC field could be repeatedly played hundreds of cycles without obvious decrease of blocking force for BP-Nafion composite-based IPCC.