Nafion Membrane Research Articles

A Membrane-Electrolyte System Approach to Understanding Ionic Conductivity and Crossover in Aqueous Organic and Metalorganic Flow Batteries

The ion exchange membrane is a critical component of most aqueous flow batteries, where it provides a transport medium for charge carrying ions while suppressing undesired crossover of redox active species. The all-vanadium redox flow battery (VRFB), the most developed flow battery chemistry to date, is also the system for which most studies of flow battery membranes have been done. These studies have shown that the concentration and composition of the acidic vanadium electrolytes influence water content in the membrane phase, and therefore influence the transport phenomena through the membrane pores. In the present work, we build on this understanding by evaluating the effects of iron(II/III) hexacyanide electrolyte concentration, pH, and cations on cation exchange membrane performance, to inform design of aqueous organic and metalorganic flow batteries (AORFBs).The size and charge numbers of established redox active materials for AORFBs afford them lower crossover than metal ions like vanadyl or iron. However, many emerging AORFB chemistries with extreme stability use neutral or alkaline electrolytes where sodium or potassium, not protons, must carry ionic current through the membrane. In these flow batteries, the membrane resistance regularly contributes the most to polarization losses. The widely-used cation exchange membrane Nafion has a factor-of-ten reduction of conductivity in potassium form compared to when it is protonated in acidic environments. Ohmic resistance of the membrane is therefore a substantial limiting factor on practical current densities and power densities for battery operation.In order to investigate the membrane-electrolyte system, we first describe simple methods for conductivity and electrolyte uptake measurements that can be used to screen a variety of membrane materials and electrolytes. We show the influence of pre-treatment, cation (sodium or potassium), supporting electrolyte, and iron hexacyanide concentration on Nafion conductivity and electrolyte uptake, and compare these results with a non-fluorinated Fumatech membrane (E-620). We also assess pre-treatment, concentration, and cation effects on ferricyanide permeability. Considering the membrane and contacting flow battery electrolyte as one system, our results emphasize that the total ion concentration of the electrolyte affects membrane water content, and there are conditions where additional supporting electrolyte can have a harmful effect on membrane conductivity. We also show that maximizing the concentration of iron hexacyanide by using mixed cation electrolytes results in increased membrane resistance, signifying that conductivity and volumetric capacity become a tradeoff.

Bioelectricity Generation Using a Crosslinked Poly(vinyl alcohol) (PVA) and Chitosan (CS) Ion Exchange Membrane in Microbial Fuel Cell

<p>Microbial fuel cells (MFCs) are a bioelectrochemical system where electrochemically active bacteria convert organic waste into electricity. Poly(vinyl alcohol) (PVA) and chitosan (CS) are polymers that have been studied as potential alternative ion exchange membranes to Nafion for many electrochemical systems. This study examined the optimal mixing ratio of PVA and chitosan CS in a PVA:CS composite membrane for MFC applications. PVA:CS composite membranes with 1:1, 2:1, and 3:1 ratios were synthesized and tested. The water uptake and ion exchange capacity, Fourier transform infrared spectra, and scanning electron microscopy images were analyzed to determine the physicochemical properties of PVA:CS membranes. The prepared membranes were applied to the ion exchange membrane of the MFC system, and their effects on the electrochemical performance were evaluated. These results showed that the composite membrane with a 3:1 (PVA:CS) ratio showed comparable performance to the commercialized Nafion membrane and produced more electricity than the other synthesized membranes. The PVA:CS membrane implemented MFCs produced a maximum power density of 0.026 mW cm<sup>−2</sup> from organic waste with stable performance. Therefore, it can be applied to a cost-effective MFC system.</p>

Evaluation of Pt particles redeposition effect on gas transport in Nafion membrane

During the operation of proton exchange membrane fuel cell, Pt particles in the catalytic layer inevitably dissolve into the membrane, which affects the performance of fuel cell. In this work, molecular dynamics is employed to investigate the effect of the redeposition of Pt particles on gas diffusion and solvation characteristics in the hydration membrane. Gas diffusion, hydrophilic cluster and its connectivity are analyzed. The interaction between Pt particles, Nafion membrane and water molecules is discussed. The influence of Pt particles on the thermal conduction of membrane is also evaluated. The results demonstrate that the presence of Pt particles affects the solvation effect of membrane, leading to a weak water cluster connectivity of membrane, which in turn leads to a poor gas diffusion performance. In addition, the thermal conductivity gradually deteriorates during the redeposition of Pt particles.

Proton transport through interfaces in nanophase-separation of hydrated aquivion membrane: Molecular dynamics simulation approach

We investigate the effect of temperature and hydration on the nanophase-separated structure and proton conductivity in Aquivion and Nafion membranes using molecular dynamics simulation method. By considering two different temperatures (298 and 353 K) and water contents (10 and 20 wt%), our study reveals that Nafion exhibits better nanophase separation and a more mature internal structure of the water phase compared to Aquivion, leading to facilitated proton dissociation and improved proton conduction through vehicular and hopping mechanisms. This study also identifies the formation of a hydronium-mediated bridge configuration that restricts vehicular mobility at low hydration, resulting in a decrease of the vehicular contribution to proton conduction. From quantitative evaluation of the extent of nanophase-separation using structure factor analysis, we find that Nafion has a shorter correlation length with greater concentration contrast in comparison to Aquivion. At high hydration conditions, the hopping mechanism dominates at low temperature while the vehicular mechanism is dominant at high temperature. At low hydration, the vehicular mechanism is significantly decreased due to hydronium-mediated bridge configurations. It is interesting to note that the proton conductivity in the Aquivion membrane is higher despite the Nafion membrane having a higher proton diffusion. We discover that the greater proton conductivity of Aquivion membrane is caused by its higher proton concentration. In general, our findings offer a fundamental knowledge of the connection between nanophase-separated structure and proton transport characteristics in Nafion and Aquivion systems under a range of temperature and hydration circumstances.

Low loading inkjet printed bifunctional electrodes for proton exchange membrane unitized regenerative fuel cells

Inkjet printing is evaluated as a feasible technique for unitized regenerative fuel cells (URFCs) electrode fabrication and to study the optimal ionomer and catalyst loading. A physical mixture of Pt, IrOx, and Nafion ionomer was inkjet printed directly on a Nafion membrane to fabricate varying loading bifunctional oxygen electrodes for a URFC and characterized via scanning electrode microscopy and cyclic voltammetry. The results show that the two catalyst do not interfere with one another and that an optimal electrode requires low ionomer loading, i.e., 10 wt%, and significantly lower amount of the IrOx catalyst compared to platinum, i.e., 3:1 Pt-IrOx ratio. A catalyst loading study shows that the highest round-trip efficiency is obtained at around 0.67 mgPt+IrOx/cm2 and further increasing the amount of catalyst does not result in a significant cell performance improvement either in water electrolysis or fuel cell mode. Overall, inkjet printing technique was used to fabricate thin bifunctional electrodes reaching round-trip efficiencies of up to 50% at 500 mA/cm2 using a bifunctional oxygen electrode with only 0.67 mgPt+IrOx/cm2 PGM catalyst loading, resulting in the highest efficiency by amount of catalyst reported to date.

Lithium-Conducting Nafion Membrane Plasticized with a DMSO–Sulfolane Mixture

Lithium-Conducting Nafion Membrane Plasticized with a DMSO–Sulfolane Mixture

Nafion-Assisted Electrochemical Detection of Copper(I) Oxide Nanoparticles Under Neutral Conditions

Herein, a rapid and straightforward electrochemical sensor was developed for the detection of Cu2O nanoparticles under neutral conditions via the use of a semipermeable Nafion membrane. This work successfully addresses the challenges associated with quantitative and onsite analysis of Cu2O nanoparticles at ultra-low concentrations. The electroreduction of Cu2O nanoparticles was significantly enhanced by improving the neutralization of the generated OH‒ ions through proton transfer facilitated by Nafion. The sensor exhibited linear detection ranges of 0.00–0.20 μg and 0.20–2.0 μg of Cu2O, with sensitivities of 107 ± 3 μA μg‒1 and 23 ± 3 μA μg‒1, respectively. The limit of detection (3SB/m) was determined to be 0.23 ng. The sensor demonstrated good reproducibility with a relative standard deviation below 5% and proved to be effective in detecting Cu2O nanoparticles in various water samples.

Self‐Diffusion of a Chemical Warfare Agent Simulant and Water in Nafion by Pulsed Field Gradient NMR

AbstractPulsed field gradient (PFG) NMR at high magnetic field was used to study microscopic diffusion of dimethyl methyl phosphonate (DMMP), a common chemical warfare agent (CWA) simulant, and water in Nafion membranes. PFG NMR measurements were performed for a broad range of molecular displacements. The self‐diffusivities were measured as a function of the DMMP concentration for several fixed water concentrations. The measured data suggest that DMMP and water diffuse in different regions of Nafion. While water mostly diffuses in hydrophilic regions of the membrane, viz. water channels, DMMP diffusion is mostly limited to interfacial perfluoroether regions between these water channels and the semi‐crystalline matrix.

Highly permselective polyvinylidene fluoride-based cation-exchange membranes containing phosphorated graphene oxide for electrodialysis

Phosphorated graphene oxide (PGO) was used to prepare polyvinylidene fluoride (PVDF)-based cation-exchange membrane for the electrodialysis (ED) process. The influences of PGO wt% on the physicochemical and electrochemical characteristics of the PVDF/PGO membranes were studied using different characterization methods. The morphology, oxidative stability, permselectivity, ion transport number, and electrochemical properties of the best PVDF/PGO membrane were compared with those of the bare Nafion-117 membrane and PVDF/GO membrane containing the same wt% of GO. The membrane containing 60 wt% PGO (PVDF/PGO60) exhibited a high water uptake of 44.69%, which was about 2.5 and 2 times higher than that achieved from PVDF/GO60 and Nafion, respectively. PVDF/PGO60 provided a considerably higher (∼10 times) ion exchange capacity (IEC) than Nafion. Electrochemical analysis revealed that Na+ ions enjoyed a high diffusion coefficient within PVDF/PGO60, which was comparable to Nafion-117. This resulted in a low area resistance of 2.4 ± 0.3 Ω cm2, high permselectivity of 96.4%, and transport number of 97.8%. Moreover, PVDF/PGO60 exhibited a low weight loss of 1.90%, and a moderate resistance change of 19.79% after being immersed in the Fenton reagent for 9 h. The desirable electrochemical properties, and oxidative and mechanical stability of PVDF/PGO60 suggest that the PGO-containing PVDF-based membranes can be considered promising CEMs for application in the electromembrane desalination processes.

Selective transport of trivalent lanthanide in electrodialysis: Limitations due to concentration polarization

Extraction of rare-earth ions from mixtures with other cations is an important part of recovering rare-earth ions from recycling or other streams. This study examines whether highly selective Donnan partitioning into a cation-exchange membrane can lead to effective electrodialysis (ED) extraction of La3+ from solutions containing monovalent or divalent ions. In Nafion membranes, trivalent La3+ sorbs selectively over Na+ and Mg2+, and the La3+/Na+ partitioning selectivity increases to values > 100 with decreasing ionic strength and/or higher ratios of Na+ to La3+ in solution. However, the experimental La3+/Na+ and La3+/Mg2+ ED selectivities are <10. The low La3+ mobility in the membrane accounts for some of the difference between partitioning and transport selectivities. Equally important, concentration polarization due to different ion transport numbers in the solution and the membrane likely leads to significant diffusion of monovalent ions through the membrane. For example, although simulated La3+/Na+ electromigration selectivities reach 35 in dilute solutions, diffusion of Na+ across the membrane reduces the overall ED transport selectivity to <10. This work shows the importance of accounting for concentration polarization when considering applications of ED for ion separations.

Efficient catalyst layer with ultra-low Pt loading for proton exchange membrane fuel cell

Developing rational structure of catalyst layer with high stability and efficient mass transport to maximize the utilization of Pt is critical to fabricate proton exchange membrane fuel cells (PEMFCs) with ultra-low Pt loading down to <100 µg cm−2. Herein, a newly designed catalyst layer with ultra-low Pt loading for PEMFC was developed using a three-dimensional graphene network (3D-GN). In the process, 3D-GN was directly grown onto an Al foil by arc discharge method, and then Pt nanoparticles were deposited by via electron beam evaporation, after the impregnation of Nafion solution and non-destructive transfer onto Nafion membrane, the electrode with Pt/3D-GN was finally fabricated. The 3D-GN possesses unique characteristics of self-supporting structure of graphene nanosheets with 3–7 layers of graphitic lattices, a high macro-porous pore volume of 19.93 mL g−1 and graphitic degree up to 74.9 %, which can provide a stable framework to support Pt nanoparticles and efficient mass transport pathways. The Pt/3D-GN as the cathode can achieve a high cell performance at ultra-low Pt loading, compared to the conventional carbon nanosphere-based electrode (CN). The maximum power density of Pt/3D-GN with 50.8 μgPt cm−2 is 1.31 W cm−2 (H2/O2, 150 kPa) and 0.64 W cm−2 (H2/Air, 150 kPa), higher than that of commercial Pt/C electrode with 100 µgPt cm−2 1.25 W cm−2 and 0.55 W cm−2 respectively. Meanwhile, the Pt/3D-GN also demonstrates excellent stability with 32 % lose after 30 k cycles (0.6 V and 0.95 V) and only 8 % decay after 5 k cycles (1.0 V–1.5 V vs RHE). The outstanding properties of 3D GN-based electrode with high activity and stability provides a new flexible platform for developing high-performance ultra-low Pt loading PEMFCs.

Porous lanthanum titanium oxide nanostructure composite membrane to enhance the power output and chemical durability of low-humidifying polymer electrolyte fuel cells: impact of additive morphology

Tuning the morphologies for improving the properties of the additive materials receives immense attention during the fabrication of proton-exchange membranes for fuel cells. This study reports the synthesis of lanthanum titanium oxide (LTO) nanostructures with different morphologies (cube, spherical, and tubular) via the pyrolysis of nanofibers containing metal precursors. A mixed matrix membrane is fabricated by incorporating LTO cubes (LTO-C), LTO spheres (LTO-S), or LTO tubes (LTO-T) into a Nafion matrix, with improved physicochemical, thermomechanical, and electrochemical properties compared to those of the unmodified Nafion and Nafion-212 membranes. We investigate the effect of LTO morphology on the performance of the Nafion membranes in low-humidity polymer electrolyte fuel cells (LH-PEFCs). The water retention and diffusion behavior of LTO-T nanostructures improve the proton conductivity and LH-PEFC performance of the Nafion composite membranes. The coexistence of La3+ and Ti4+ affords efficient radical scavenging during long-term LH-PEFC operation, which realizes higher durability for the composite membranes compared to Nafion. Accordingly, this study proposes a novel strategy to resolve the major challenges associated with the operation of LH-PEFCs with Nafion membranes: dehumidification and oxidative degradation.

Novel Proton Exchange Membranes Based on Sulfonated Poly(acrylonitrile-co-glycidyl methacrylate)/Poly(vinyl chloride) Composite

In this study, novel proton exchange membranes (PEMs) based on a composite of sulfonated polyacrylonitrile (SPAN), sulfonated polyglycidyl methacrylate (SPGMA), or sulfonated poly(acrylonitrile-co-glycidyl methacrylate) (SP(AN-co-GMA))/polyvinyl chloride (PVC) were developed to be used for direct methanol fuel cells (DMFCs). After polymerization and sulfonation of the prepared polymers, the polyelectrolyte membranes were prepared by the casting and solvent evaporation technique for sulfonated homo- or co-polymers with polyvinyl chloride (PVC) composites. The resulting membranes were characterized by Fourier infrared and Raman spectral analyses, X-ray diffractometry, and scanning electron microscopy. The findings of this study reveal that both the thermal stability and ion exchange capacity of the composite membranes based on sulfonated copolymers were higher than that of their corresponding composites based on sulfonated homopolymers. In this context, the weight loss percentage of the prepared composite polyelectrolyte membranes did not exceed 12% of their initial weights. The IEC of all the composite membranes ranged from 0.18 to 0.48 meq/g. Thus, the IEC value increased with the increasing proportion of the glycidyl methacrylate comonomer. Moreover, the prepared PEMs based on SP(AN-co-GMA)/PVC composites showed lower methanol permeability (8.7 × 10−7 cm2/s) than that of the Nafion membranes (3.39 × 10−6 cm2/s). Therefore, these prepared PEMs are a good candidate for DMFCs applications.

Robust Proton Conduction against Mechanical Stress in Flexible Free‐Standing Membrane Composed of Two‐Dimensional Coordination Polymer

AbstractIntroduction of mechanical flexibility into proton‐conducting coordination polymers (CPs) is in high demand for future protonic applications such as fuel cells and hydrogen sensors. Although such mechanical properties have been primarily investigated in one‐dimensional (1D) CPs, in this study, we successfully fabricated highly flexible free‐standing CP membranes with a high surface‐to‐volume ratio, which is beneficial for enhanced performance in the aforementioned applications. We fabricated a layered CP, Cu2(NiTCPP) (H4(H2TCPP); 5,10,15,20‐tetrakis(4‐carboxyphenyl) porphyrin), in which a two‐dimensional (2D) square grid sheet composed of tetradentate nickel porphyrins and paddlewheel‐type copper dimers was connected to each other by weak van der Waals forces. The mechanical flexibility was evaluated by bending and tensile tests. The flexural and Young's moduli of the membrane were significantly higher than those of conventional Nafion membranes. Electrochemical impedance spectroscopy analysis revealed that the in‐plane proton conductivity of the membrane was maintained even under applied bending stress. Because the X‐ray diffraction analysis indicates that the proton‐conducting pathway through the hydrogen bonding network remains intact during the bending operation, our present study provides a promising strategy for the fabrication of new and advanced 2D CPs without using substrates or additional polymers for protonic devices.

Silane cross-linked network and concentrated flexible sulfoalkyl groups for forming a novel C-SPAEK membrane with enhanced methanol resistance and proton conductivity for DMFC applications

In the present work, a novel poly(arylene ether ketone) with a unique molecular design that included concentrated flexible sulfoalkyl groups and a silane cross-linked network (C-SPAEK) was prepared and used as a PEM for DMFCs. The chemical structures, sulfonation degree and phase-separated morphology were characterized and identified by 1H NMR, FT-IR and SAXS. The resulting copolymers exhibited excellent thermal stability (T5%>263.8 °C) and mechanical properties (tensile strength>52.88 MPa). Additionally, the high IEC values and obvious hydrophilic/hydrophobic phase-separated structure (d > 2.71 nm) ensured that the C-SPAEK membranes possessed high proton conductivities. The C-SPAEK PEMs also displayed enhanced methanol resistance and dimensional stability, which were much better than those of a recast Nafion membrane under the same conditions. The C-SPAEK-0.4 membrane maintained a low methanol absorption of less than 48.7%, even in 4 M methanol solution. In particular, the C-SPAEK-0.6 membrane exhibited the best comprehensive performance, with a high proton conductivity (0.164 S cm−1), low methanol uptake (52.1%) and permeability (3.63 × 10−7 cm2 s−1), and maximum power density (83.2 mW cm−2), when immersed in 2 M methanol at 80 °C in a DMFC single-cell. These results suggested that the C-SPAEK membranes were sufficiently tough and had the potential to overcome the problems caused by the high methanol permeability of PEMs. The unique molecular design of C-SPAEK guaranteed a rare combination of high proton conductivity and enhanced methanol resistance, which are the key determining factors for DMFC applications.

Robust Proton Conduction against Mechanical Stress in Flexible Free-Standing Membrane Composed of Two-Dimensional Coordination Polymer.

Introduction of mechanical flexibility into proton-conducting coordination polymers (CPs) is in high demand for future protonic applications such as fuel cells and hydrogen sensors. Although such mechanical properties have been primarily investigated in one-dimensional (1D) CPs, in this study, we successfully fabricated highly flexible free-standing CP membranes with a high surface-to-volume ratio, which is beneficial for enhanced performance in the aforementioned applications. We fabricated a layered CP, Cu2 (NiTCPP) (H4 (H2 TCPP); 5,10,15,20-tetrakis(4-carboxyphenyl) porphyrin), in which a two-dimensional (2D) square grid sheet composed of tetradentate nickel porphyrins and paddlewheel-type copper dimers was connected to each other by weak van der Waals forces. The mechanical flexibility was evaluated by bending and tensile tests. The flexural and Young's moduli of the membrane were significantly higher than those of conventional Nafion membranes. Electrochemical impedance spectroscopy analysis revealed that the in-plane proton conductivity of the membrane was maintained even under applied bending stress. Because the X-ray diffraction analysis indicates that the proton-conducting pathway through the hydrogen bonding network remains intact during the bending operation, our present study provides a promising strategy for the fabrication of new and advanced 2D CPs without using substrates or additional polymers for protonic devices.

Acquiring reliable hydrogen crossover data of hydrated ion exchange membranes to elucidate the ion conducting channel morphology

The morphology of ion channels within ion exchange membranes (IEM) has long been disputed by researchers. Several accepted models include the Gierke’s discrete spherical cluster model, continuous parallel cylinder model, and flat-layered model. The primary experimental data to support each model were mostly small-angle X-ray spectroscopy (SAXS). In this work, we propose that hydrogen permeability (i.e. crossover) data of hydrated IEMs could provide valuable insights into understanding the ion channel connectivity and continuity within the membrane. We re-derived the two-phase Maxwell-Eucken transport models to predict the hydrogen crossover of hydrated IEMs. The model accurately predicted the hydrogen crossover of Nafion and in-house BPSH membrane series within 10% error range. The predicted results were experimentally validated using the pressure decay method (PDM) developed in our group specifically for this purpose. By comparing the degree of change in hydrogen crossover between the dry and hydrated membranes, it was possible to extract semi-qualitative information about the membrane’s controversial ion-conducting channel morphology. Interestingly, our experimental data and model prediction corroborates with the Gierke’s conjecture that the water phase within the ion channel exists as discrete spherical clusters, not as the continuous percolated phase (the parallel cylinder model). Although there is yet no consensus on the internal morphology of ion channels, our work suggests that hydrogen crossover data can be useful in elucidating the ion channel morphology.

Electrospun phosphonated poly(pentafluorostyrene) nanofibers as a reinforcement of Nafion membranes for fuel cell application

Nafion is a well-known perfluorosulfonic acid membrane widely used in fuel cells. However, despite its excellent properties, Nafion has limitations, including high hydrogen crossover. Reducing the hydrogen crossover is crucial since the H2 permeating through the membrane can directly react with O2 and produce radicals that can degrade Nafion. The hydrogen crossover can be minimized by increasing membrane thickness or by embedding nanostructures into Nafion. In this work, we report Nafion membranes reinforced by electrospun fibers made from phosphonated polypentafluorostyrene (PWN70) and, for comparison, unmodified polypentafluorostyrene (PPFSt). Composite membranes were obtained by spray-coating of Nafion onto the nanofiber meshes to fill the voids. From tensile tests, we found that PWN70/Nafion and PPFSt/Nafion composite membranes show higher Young's modulus and higher yield stress than pure Nafion. Fuel cell tests showed that PPFSt/Nafion composite membranes suffer from performance losses with increasing fiber loading, whereas PWN70/Nafion composite membranes perform similarly with non-reinforced Nafion. Furthermore, the use of PWN70/Nafion resulted in an H2 crossover reduction by 37–40% for atmospheric pressure, while it was not improved when using PPFSt/Nafion composite membranes. These results show the advantages of PWN70 nanofibers as a reinforcement for Nafion, which reduce the hydrogen crossover without sacrificing proton conductivity.

An Amperometric Biosensor Based on a Bilayer of Electrodeposited Graphene Oxide and Co-Crosslinked Tyrosinase for L-Dopa Detection in Untreated Human Plasma.

L-Dopa, a bioactive compound naturally occurring in some Leguminosae plants, is the most effective symptomatic drug treatment for Parkinson's disease. During disease progression, fluctuations in L-DOPA plasma levels occur, causing motor complications. Sensing devices capable of rapidly monitoring drug levels would allow adjusting L-Dopa dosing, improving therapeutic outcomes. A novel amperometric biosensor for L-Dopa detection is described, based on tyrosinase co-crosslinked onto a graphene oxide layer produced through electrodeposition. Careful optimization of the enzyme immobilization procedure permitted to improve the long-term stability while substantially shortening and simplifying the biosensor fabrication. The effectiveness of the immobilization protocol combined with the enhanced performances of electrodeposited graphene oxide allowed to achieve high sensitivity, wide linear range, and a detection limit of 0.84 μM, suitable for L-Dopa detection within its therapeutic window. Interference from endogenous compounds, tested at concentrations levels typically found in drug-treated patients, was not significant. Ascorbic acid exhibited a tyrosinase inhibitory behavior and was therefore rejected from the enzymatic layer by casting an outer Nafion membrane. The proposed device was applied for L-Dopa detection in human plasma, showing good recoveries.

Fabrication and Performance Evaluation of a Cation Exchange Membrane Using Graphene Oxide/Polyethersulfone Composite Nanofibers.

Ion exchange membranes, especially cation exchange membranes (CEMs), are an important component in membrane-based energy generation and storage because of their ability to transport cations via the electrochemical potential gradient while preventing electron transport. However, developing a CEM with low areal resistance, high permselectivity, and stability remains difficult. In this study, electrospun graphene oxide/polyethersulfone (GO/PES) composite nanofibers were prepared with varying concentrations of GO. To fabricate a CEM, the pores of the electrospun GO/PES nanofiber substrates were filled with a Nafion ionomer. The pore-filled PES nanofiber loaded with 1% GO revealed a noticeable improvement in hydrophilicity, structural morphology, and mechanical properties. The 1% GO/PES pore-filled CEM was compared to a Nafion membrane of a varying thickness and without a nanofiber substrate. The CEM with a nanofiber substrate showed permselectivity of 85.75%, toughness of 111 J/m3, and areal resistance of 3.7 Ω cm2, which were 12.8%, 4.3 times, and 4.0 times better, respectively, than those of the Nafion membrane at the same thickness. The development of a reinforced concrete-like GO/PES nanofiber structure containing stretchable ionomer-enhanced membrane surfaces exhibited suitable areal resistance and reduced the thickness of the composite membrane without compromising the mechanical strength, suggesting its potential application as a cation exchange membrane in electrochemical membrane-based systems.