Showing papers on "Nafion published in 2018"
TL;DR: The authors report the green synthesis of a zirconium, amino acid-based MOF that displays high proton conductivity and excellent stability and is one of the most promising candidates to approach the commercial benchmark Nafion.
Abstract: Proton conductive materials are of significant importance and highly desired for clean energy-related applications. Discovery of practical metal-organic frameworks (MOFs) with high proton conduction remains a challenge due to the use of toxic chemicals, inconvenient ligand preparation and complication of production at scale for the state-of-the-art candidates. Herein, we report a zirconium-MOF, MIP-202(Zr), constructed from natural α-amino acid showing a high and steady proton conductivity of 0.011 S cm−1 at 363 K and under 95% relative humidity. This MOF features a cost-effective, green and scalable preparation with a very high space-time yield above 7000 kg m−3 day−1. It exhibits a good chemical stability under various conditions, including solutions of wide pH range and boiling water. Finally, a comprehensive molecular simulation was carried out to shed light on the proton conduction mechanism. All together these features make MIP-202(Zr) one of the most promising candidates to approach the commercial benchmark Nafion.
186 citations
TL;DR: Aryl ether-free poly(fluorene) ionomer was used in this article to minimize undesirable phenyl group interaction with hydrogen oxidation catalysts and achieved a peak power density of 146 W cm−2, approaching that of Nafion-based PEMFCs.
Abstract: Alkaline membrane fuel cells (AMFCs) show great potential as alternative energy conversion devices to acidic proton exchange membrane fuel cells (PEMFCs) Over the last decade, there has been significant progress in the development of alkaline-stable polyaromatic materials for membrane separators and ionomeric binders for AMFCs However, the AMFC performance using polyaromatic ionomers is generally poor, ca a peak power density of <400 mW cm−2 Here, we report a rational design for polyaromatic ionomers which can minimize undesirable phenyl group interaction with hydrogen oxidation catalysts The AMFC using a newly designed aryl ether-free poly(fluorene) ionomer exhibits a peak power density of 146 W cm−2, which is approaching that of Nafion-based PEMFCs This study further discusses the remaining challenges of high-performing AMFCs
176 citations
TL;DR: A cross-linked polyacrylonitrile (PAN)-based cation exchange membrane that is low cost and mechanically robust and enables exceptionally long cyclability of Zn/Zn symmetric cells with low polarization and effective dendrite suppression.
Abstract: Aqueous batteries with zinc metal anodes are promising alternatives to Li-ion batteries for grid storage because of their abundance and benefits in cost, safety, and nontoxicity. However, short cyclability due to zinc dendrite growth remains a major obstacle. Here, we report a cross-linked polyacrylonitrile (PAN)-based cation exchange membrane that is low cost and mechanically robust. Li2S3 reacts with PAN, simultaneously leading to cross-linking and formation of sulfur-containing functional groups. Hydrolysis of the membrane results in the formation of a membrane that achieves preferred cation transport and homogeneous ionic flux distribution. The separator is thin (30 μm-thick), almost 9 times stronger than hydrated Nafion, and made of low-cost materials. The membrane separator enables exceptionally long cyclability (>350 cycles) of Zn/Zn symmetric cells with low polarization and effective dendrite suppression. Our work demonstrates that the design of new separators is a fruitful pathway to enhancing th...
165 citations
TL;DR: In this article, Nafion/Fe3O4-SGO composite membranes were applied as potential proton exchange membranes in Proton Exchange Membrane Fuel Cell (PEMFC) operated at high temperature and low humidity.
Abstract: Iron oxide (Fe3O4) nanoparticles anchored over sulfonated graphene oxide (SGO) and Nafion/Fe3O4–SGO composites were fabricated and applied as potential proton exchange membranes in proton exchange membrane fuel cells (PEMFCs) operated at high temperature and low humidity. Fe3O4 nanoparticles bridge SGO and Nafion through electrostatic interaction/hydrogen bonding and increased the intrinsic thermal and mechanical stabilities of Nafion/Fe3O4–SGO composite membranes. Nafion/Fe3O4–SGO composite membranes increased the compactness of ionic domains and enhanced the water absorption and proton conductivity while restricting hydrogen permeability across the membranes. The proton conductivity of Nafion/Fe3O4–SGO (3 wt%) composite membrane at 120 °C under 20% relative humidity (RH) was 11.62 mS cm−1, which is 4.74 fold higher than that of a pristine recast Nafion membrane. PEMFC containing the Nafion/Fe3O4–SGO composite membrane delivered a peak power density of 258.82 mW cm−2 at a load current density of 640.73 mA cm−2 while operating at 120 °C under 25% RH and ambient pressure. In contrast, under identical operating conditions, a peak power density of only 144.89 mW cm−2 was achieved with the pristine recast Nafion membrane at a load current density of 431.36 mA cm−2. Thus, Nafion/Fe3O4–SGO composite membranes can be used to address various critical problems associated with commercial Nafion membranes in PEMFC applications.
165 citations
TL;DR: It is demonstrated that well-controlled hairpin chain folding can be utilized for proton conductivity within a crystalline polymer structure, and it is projected that this structure could be adapted for ion transport.
Abstract: Recent advances in polymer synthesis have allowed remarkable control over chain microstructure and conformation. Capitalizing on such developments, here we create well-controlled chain folding in sulfonated polyethylene, leading to highly uniform hydrated acid layers of subnanometre thickness with high proton conductivity. The linear polyethylene contains sulfonic acid groups pendant to precisely every twenty-first carbon atom that induce tight chain folds to form the hydrated layers, while the methylene segments crystallize. The proton conductivity is on par with Nafion 117, the benchmark for fuel cell membranes. We demonstrate that well-controlled hairpin chain folding can be utilized for proton conductivity within a crystalline polymer structure, and we project that this structure could be adapted for ion transport. This layered polyethylene-based structure is an innovative and versatile design paradigm for functional polymer membranes, opening doors to efficient and selective transport of other ions and small molecules on appropriate selection of functional groups.
161 citations
TL;DR: In this paper, a novel and sensitive non-enzymatic glucose sensor was developed based on the modification of Au@Cu2O nanocomposite on the surface of glassy carbon (Au@cu2O/Nafion/GC) electrode.
Abstract: A novel and sensitive non-enzymatic glucose sensor was developed based on the modification of Au@Cu2O nanocomposite on the surface of glassy carbon (Au@Cu2O/Nafion/GC) electrode. Au@Cu2O nanocomposites were prepared using a facile chemical reduction method and its core-shell structure was confirmed by transmission electron microscopy (TEM) and element analyses, in which the diameter of Au nanoparticle (NP) is about 14 nm and the thickness of shell is about 30–50 nm, being composed of Cu2O nanoparticles. Electrochemical properties of Au@Cu2O/Nafion/GC electrode were investigated by cyclic voltammetric techniques and electrochemical impedance spectroscopy (EIS). It was found that the Au@Cu2O/Nafion/GC electrode exhibited enhanced electrocatalytic activity towards glucose oxidation in alkaline medium (pH = 12.6), as compared to those of Cu2O/Nafion/GC and Au/Nafion/GC electrodes. Some influence parameters including pH value and Au@Cu2O content on electrocatalytic activity of the modified electrode have been investigated. Under the optimized conditions, the electrochemical sensor has a linear dependence over glucose concentrations from 0.05 to 2.0 mM with a sensitivity of 715 μA mM−1 Cm−2. Moreover, such a glucose sensor demonstrated good stability, reproducibility and selectivity. Our results suggest that Au@Cu2O core-shell structure could be a promising candidate for the construction of non-enzymatic sensor.
152 citations
TL;DR: A rotaxane based polymer entity assembled via host–guest interaction is reported and it is proved that by exploiting the thermally triggered translational motion of mechanically bonded rotAXane, exceptionally fast proton transfer can be fulfilled at an external thermal input.
Abstract: Synthetic polyelectrolytes, capable of fast transporting protons, represent a challenging target for membrane engineering in so many fields, for example, fuel cells, redox flow batteries, etc. Inspired by the fast advance in molecular machines, here we report a rotaxane based polymer entity assembled via host–guest interaction and prove that by exploiting the thermally triggered translational motion (although not in a controlled manner) of mechanically bonded rotaxane, exceptionally fast proton transfer can be fulfilled at an external thermal input. The relative motion of the sulfonated axle to the ring in rotaxane happens at ~60 °C in our cases and because of that a proton conductivity (indicating proton transfer rate) of 260.2 mS cm−1, which is much higher than that in the state-of-the-art Nafion, is obtained at a relatively low ion-exchange capacity (representing the amount of proton transfer groups) of 0.73 mmol g−1. Proton exchange is critical in many applications, such as in conductive proton exchange membranes, but achieving fast proton exchange still remains a challenge. Here the authors report fast proton exchange in a rotaxane based polymer by exploiting thermally triggered translational motion of the mechanically bonded rotaxane.
150 citations
TL;DR: A molecular-level hybridization for nanophase-separated Nafion using 2-5 nm quantum dots (QDs) as a new smart filler is demonstrated and a distinctive synthesis of subordinate-assembly, in which QDs are driven by the self-assembly of Nafions affinity chains, results in a precise distribution of QDs in the ionic, or backbone, nanophases of NAFion.
Abstract: Nanophase-separated membranes hold promise for fast molecule or ion transfer. However, development and practical application are significantly hindered by both the difficulty of chemical modification and nanophase instability. This can be addressed by organic-inorganic hybridization of functional fillers with a precise distribution in specific nanophase. Here, a molecular-level hybridization for nanophase-separated Nafion using 2-5 nm quantum dots (QDs) as a new smart filler is demonstrated. Two kinds of QDs are prepared and used: hydrophilic polymer-like QDs (PQDs) and hydrophobic graphene oxide QDs (GQDs). Because of selective interactions, QDs offer advantages of matched structural size and automatic recognition with the nanophase. A distinctive synthesis of subordinate-assembly, in which QDs are driven by the self-assembly of Nafion affinity chains, is reported. This results in a precise distribution of QDs in the ionic, or backbone, nanophases of Nafion. The resulting PQDs in the ionic nanophase significantly increase membrane proton conduction and device output-power without loss of mechanical stability. This is difficult to realize with conventional fillers. The GQDs in the backbone nanophase reduce the crystallinity and significantly augment membrane water uptake and swelling capacities.
114 citations
TL;DR: The fabrication of healable PEMs that exhibit satisfactory mechanical stability, enhanced proton conductivity, and suppressed methanol permeability via hydrogen-bonding complexation between Nafion and poly(vinyl alcohol) (PVA) followed by postmodification with 4-carboxybenzaldehyde (CBA) molecules is presented.
Abstract: Proton-exchange membranes (PEMs) that can heal mechanical damage to restore original functions are important for the fabrication of durable and reliable direct methanol fuel cells (DMFCs). The fabrication of healable PEMs that exhibit satisfactory mechanical stability, enhanced proton conductivity, and suppressed methanol permeability via hydrogen-bonding complexation between Nafion and poly(vinyl alcohol) (PVA) followed by postmodification with 4-carboxybenzaldehyde (CBA) molecules is presented. Compared with pure Nafion, the CBA/Nafion-PVA membranes exhibit enhanced mechanical properties with an ultimate tensile strength of ≈20.3 MPa and strain of ≈380%. The CBA/Nafion-PVA membrane shows a proton conductivity of 0.11 S cm-1 at 80 °C, which is 1.2-fold higher than that of a Nafion membrane. The incorporated PVA gives the CBA/Nafion-PVA membranes excellent proton conductivity and methanol resistance. The resulting CBA/Nafion-PVA membranes are capable of healing mechanical damage of several tens of micrometers in size and restoring their original proton conductivity and methanol resistance under the working conditions of DMFCs. The healing property originates from the reversibility of hydrogen-bonding interactions between Nafion and CBA-modified PVA and the high chain mobility of Nafion and CBA-modified PVA.
114 citations
TL;DR: Proton conductivities in Su-CNTs/Nafion composite membranes were remarkably enhanced due to the mass formation of proton-conducting pathways (water channels) along the Su- CNTs, which interconnected the isolated ionic-water clusters at low humidity and resulted in less tortuosity of the water channel network for proton transportation at high humidity.
Abstract: Proton exchange membrane fuel cell (PEMFC) is one of the most promising green power sources, in which perfluorinated sulfonic acid ionomer-based membranes (e.g., Nafion) are widely used. However, the widespread application of PEMFCs is greatly limited by the sharp degradation in electrochemical properties of the proton exchange membranes under high temperature and low humidity conditions. In this work, the high-performance sulfonated carbon nanotubes/Nafion composite membranes (Su-CNTs/Nafion) for the PEMFCs were prepared and the mechanism of the microstructures on the macroscopic properties of membranes was intensively studied. Microstructure evolution in Nafion membranes during water uptake was investigated by positron annihilation lifetime spectroscopy, and results strongly showed that the Su-CNTs or CNTs in Nafion composite membranes significantly reinforced Nafion matrices, which influenced the development of ionic-water clusters in them. Proton conductivities in Su-CNTs/Nafion composite membranes we...
109 citations
TL;DR: In this article, the state-of-the-art and progress on polymer electrolyte membranes engineered using graphene and graphene oxide, as well as their synthesis routes and the influence on the performance are discussed.
Abstract: The proton exchange membrane fuel cell (PEMFC) converts chemical energy into electrical energy via electrochemical reaction between hydrogen and oxygen, with heat and water as byproducts. When a PEMFC is engineered with polymer electrolyte membrane, e.g., Nafion and polybenzimidazole (PBI), it helps to enhance the performance of the fuel cell under monitored environmental conditions, i.e., high proton conductivity, improved electrode kinetics, and tailoring of properties, along with low tolerance for carbon monoxide. Recently discovered “graphene” has enticed the scientific community, because of its exceptional properties. As per the literature, PEMFCs engineered with graphene can yield high power density, along with 38% enhanced current density, and 257% improved ionic conductivity. In this context, the present review gives the state-of-the-art and progress on polymer electrolyte membranes engineered using graphene and graphene oxide, as well as their synthesis routes and the influence on the performance...
TL;DR: KAUST 7' exhibited a superprotonic conductivity as evidenced by the impedance spectroscopic measurement revealing an exceptional conductivity up to 2.0 × 10-2 S cm-1 at 363 K and under 95% RH, a performance maintained over 7 days.
Abstract: A hydrolytically stable metal–organic framework (MOF) material, named KAUST-7′, was derived from a structural phase change of KAUST-7 upon exposure to conditions akin to protonic conduction (363 K/95% relative humidity). KAUST 7′ exhibited a superprotonic conductivity as evidenced by the impedance spectroscopic measurement revealing an exceptional conductivity up to 2.0 × 10–2 S cm–1 at 363 K and under 95% RH, a performance maintained over 7 days. Ab initio molecular dynamics simulations suggested that the water-mediated proton transport mechanism is governed by water assisted reorganization of the H-bond network involving the fluorine moieties in KAUST-7′ and the guest water molecules. The notable level of performances combined with a very good hydrolytic stability positions KAUST-7′ as a prospective proton-exchange membrane alternative to the commercial benchmark Nafion. Furthermore, the remarkable RH sensitivity of KAUST-7′ conductivity, substantially higher than previously reported MOFs, offers great ...
TL;DR: In this paper, a functional separator is designed to improve the utilization of sulfur and to inhibit polysulfide shuttling for high performance lithium-sulfur (Li-S) batteries.
Abstract: A functional separator is designed to improve the utilization of sulfur and to inhibit polysulfide shuttling for high performance lithium–sulfur (Li–S) batteries. Here, we demonstrate a functional separator which is obtained by coating sulfonated UiO-66 metal–organic framework (MOF)/Nafion on a polyethylene separator. This modified separator suppresses the polysulfide diffusion due to a molecular sieving and electrostatic repulsion effect and facilitates the redox kinetics of sulfur conversion because of a fast charge transport by sulfonic groups tethered to the MOF and Nafion. Thus, the Li–S cells based on the MOF/Nafion hybrid-coated separator achieve a discharge capacity of 1127.4 mA h g−1 at 0.1C, a capacity retention of 66.8% at 3C relative to 0.1C, and a cycling stability of 75.5% over 200 charging/discharging cycles. These values are much greater than those of pristine and Nafion-coated separators, which confirms the superiority of MOF/Nafion hybrid coating layers for the design of functional separators.
TL;DR: In this paper, a proton-conducting sulfonated poly(ether sulfone)-metal-organic framework membrane with high proton conductivity at high temperature and anhydrous conditions was synthesized by anchoring the Cr-MIL-101-NH2 to the aromatic polymer backbone via a Hinsberg reaction.
TL;DR: The results show that the use of smaller copper nanoparticles leads to a higher ethylene production with a remarkable high FE, at the same time, diminishing the competitive hydrogen evolution reaction in terms of FE.
Abstract: Copper-based surfaces appear as the most active catalysts for CO2 electroreduction to hydrocarbons, even though formation rates and efficiencies still need to be improved. The aim of the present work is to evaluate the continuous gas-phase CO2 electroreduction to hydrocarbons (i.e. ethylene and methane) at copper nanoparticulated-based surfaces, paying attention to particle size influence (ranging from 25–80 nm) on reaction productivity, selectivity, and Faraday efficiency (FE) for CO2 conversion. The effect of the current density and the presence of a microporous layer within the working electrode are then evaluated. Copper-based gas diffusion electrodes are prepared by airbrushing the catalytic ink onto carbon supports, which are then coupled to a cation exchange membrane (Nafion) in a membrane electrode assembly. The results show that the use of smaller copper nanoparticles (25 nm) leads to a higher ethylene production (1148 μmol m−2 s−1) with a remarkable high FE (92.8%), at the same time, diminishing the competitive hydrogen evolution reaction in terms of FE. This work demonstrates the importance of nanoparticle size on reaction selectivity, which may be of help to design enhanced electrocatalytic materials for CO2 valorization to hydrocarbons.
TL;DR: The device stability is obviously enhanced because of the hydrophobicity and chemical and mechanical stability of the Nafion polymer that is enriched on the surface of the PEDOT:PSS film.
Abstract: In PIN-type perovskite solar cells (PSCs), the hydroscopicity and acidity of the poly(3,4-ethylenedioxythiophene)-poly(styrene-sulfonate) (PEDOT:PSS) hole transport layer (HTL) have critical influences on the device stability. To eliminate these problems, Nafion, the hydrophobic perfluorosulfonic copolymer, is incorporated into PEDOT:PSS by a simple spin-coating process. For the modified film, Nafion/PSSH (poly(styrene sulfonate) acid) acts as an electron-blocking layer on the surface and the PEDOT-rich domain tends to gather into larger particles with better interchain charge transfer inside the film. Consequently, the modified PEDOT:PSS HTL shows enhanced conductivity and light transmittance as well as more favorable work function, ending up with the increased short-circuit current density (Jsc) and open-circuit voltage (Voc) of the device. Finally, PSCs with Nafion-modified HTLs achieve the best power conversion efficiency of 16.72%, with 23.76% improvement compared with PEDOT:PSS-only devices (13.51%)...
TL;DR: In this article, the authors describe the fabrication of layered membranes, which consist of a 40µm thick porous Nafion layer and a 2−17‵m thin PBI blocking layer.
TL;DR: Observations of the effect of ionomer:carbon ratio and a comparison between carbons of different surface areas provided insights on the microstructure of the catalyst ink corresponding to the optimized I/ C ratio for fuel cell performance reported in the literature.
Abstract: We present a rheological investigation of fuel cell catalyst inks. The effects of ink parameters, which include carbon black-support structure, Pt presence on carbon support (Pt-carbon), and ionomer (Nafion) concentration, on the ink microstructure of catalyst inks were studied using rheometry in combination with ultrasmall-angle X-ray scattering (USAXS) and dynamic light scattering (DLS). Dispersions of a high-surface-area carbon (HSC), or Ketjen black type, demonstrated a higher viscosity than Vulcan XC-72 carbon due to both a higher internal porosity and a more agglomerated structure that increased the effective particle volume fraction of the inks. The presence of Pt catalyst on both the carbon supports reduced the viscosity through electrostatic stabilization. For carbon-only dispersions (without Pt), the addition of ionomer up to a critical concentration decreased the viscosity due to electrosteric stabilization of carbon agglomerates. However, with Pt-carbon dispersions, the addition of ionomer showed contrasting behavior between Vulcan and HSC supports. In the Pt-Vulcan dispersions, the effect of ionomer addition on the rheology was qualitatively similar to Vulcan dispersions without Pt. The Pt-HSC dispersions showed an increased viscosity with ionomer addition and a strong shear-thinning nature, indicating that Nafion likely flocculated the Pt-HSC aggregates. These results were verified using DLS and USAXS. Further, the observations of the effect of ionomer:carbon ratio and a comparison between carbons of different surface areas provided insights on the microstructure of the catalyst ink corresponding to the optimized I/ C ratio for fuel cell performance reported in the literature.
TL;DR: In this paper, a ternary composite membrane consisting of SPEEK/poly (vinyl alcohol) (PVA) and tetraethyl ortosilicate (TEOS) was prepared by blending and casting method.
TL;DR: It is demonstrated here that the combination of functional (ionomer coating on separator) and nonfunctional (extra cathode layer) physical barriers effectively suppresses the polysulfide crossover and improves the electrochemical performance of Li-S batteries.
Abstract: Minimizing the shuttle effect by constraining polysulfides to the cathode compartment and activating the passive layer between cathode and separator are highly important for improving the Li–S cell performance, Coulombic efficiency, and cycle life. Here, we report a submicron thin coating of permselective sulfonated poly(ether ether ketone) (SPEEK) composite layer on the separator that would reduce polysulfide crossover, imparting a significant improvement in cycle life. It is observed that SPEEK increases the stability, and adding Nafion improves the capacity value. Among different ratios of Nafion and SPEEK (25:75, 50:50, and 75:25), the composite with a SPEEK/Nafion ratio of 50:50 showed a controlled shuttle effect with a stable cell capacity of 600 mA h g–1 up to 300 cycles. This modified separator with permselective coatings not only reduces the polysulfide shuttle but also improves the wettability and interfacial contact, which results in an improvement in average cell potential and lithium diffusiv...
TL;DR: Sulfonated poly(ether ether-ketone) (SPEEK) hybrid membranes containing polydopamine-decorated multiwalled carbon nanotubes (MWCNTs@PDA) as the interfacial modifier have been fabricated in this article.
TL;DR: Results indicate that the approach proposed here is an ideal option to prepare amphiprotic membranes for VFBs with high efficiency and good durability and that the VFB single cell with this membrane achieves a high energy efficiency that is higher than those of Nafion 212 and other reported amphiprotsic membranes.
Abstract: A novel amphiprotic side-chain-functionalized membrane was for the first time designed for vanadium redox flow battery (VFB). Different from frequently used blending amphiprotic membranes, the one proposed here is allowed to possess high anion-exchange capacity (IECa) without sacrificing the cation-exchange capacity (IECc) because both IECa and IECc increased with the grafting degree of side chains. Having a high IECa, the membrane prepared here exhibits an ultralow vanadium permeability (<10–8 cm2 s–1), which leads to very high Coulombic efficiencies (97–98% at 40–200 mA cm–2) of VFB and good cell self-discharge durability. Moreover, the high IECc contributes to a decent ionic conductivity (area resistance: 0.5 Ω cm–2), which ensures a high-voltage efficiency of the cell. On the basis of these good properties, the VFB single cell with this membrane achieves a high energy efficiency (e.g., 77.4% at 200 mA cm–2) that is higher than those of Nafion 212 and other reported amphiprotic membranes. These results...
TL;DR: The fabricated MIP sensor was successfully applied in the determination of DA concentrations in injection and human serum samples with satisfactory recoveries and good reproducibility, long-term stability and favorable selectivity were obtained in the experiment.
TL;DR: In this paper, the interaction between silica and different types of polymer matrices in fuel cells and how they boost fuel cell performance is discussed and the current challenges of silica-related membrane-based fuel cells are discussed.
TL;DR: In this article, a non-destructive swelling-filling (SF) strategy is applied for inorganic modification on Nafion by using functionalized silica (F-silica) nanoparticles as fillers.
TL;DR: In this paper, a new porous graphene (PGR) based nanocomposite was synthesized by a chemical and thermal reduction of graphite oxide in the assistance of calcium lignosulfonate (CLS), and characterized by scanning electron microscopy SEM, TEM, XPS, Zeta potential analysis, FTIR and EIS.
Abstract: Here, a new porous graphene (PGR) based nanocomposite was synthesized by a chemical and thermal reduction of graphite oxide in the assistance of calcium lignosulfonate (CLS), and characterized by scanning electron microscopy SEM, TEM, XPS, Zeta potential analysis, FTIR and EIS. Then the as-prepared CLS/PGR was used along with Nafion to modify a glassy carbon electrode (GCE) for constructing electrochemical sensor to detect Pb2+ and Cd2+ simultaneously. Compared with the bare GCE, the reduced graphene oxide/GCE, and the CLS/PGR/GCE, the Nafion/CLS/PGR/GCE exhibited improved electrochemical performance in detecting the two ions. It could be ascribed to the synergistic contribution from PGR, CLS and Nafion, which integrated the advantageous features of high active surface area, good cation exchange ability and strong adsorption capacity. Under optimum conditions, this novel sensor showed a wide detection range for Pb2+ and Cd2+ (0.05–5.0 μM) with the limit of detection and limit of quantification for Pb2+ 0.01 and 0.03 μM, for Cd2+ 0.003 and 0.01 μM, respectively. It was successfully applied for the simultaneous determination of Pb2+ and Cd2+ in real water samples with satisfying recoveries of 93.6–105.3% for Pb2+ and 93.5–102.5% for Cd2+, demonstrating its feasibility for the determination of environmental metallic pollutants.
TL;DR: In this article, Nafion-tungsten oxide hybrid membranes, [Nafion/(WO3)x], with varying loading levels of WO3 nanofiller (x = 0, 0.024, and 0.329) are prepared and investigated as candidates for application as solid electrolytes in vanadium redox flow batteries (VRFBs).
TL;DR: In this article, diamine modified Graphene oxide (MGO) has been synthesized and mixed with Nafion polymer to form a hybrid film, and applied to the humidity sensors.
Abstract: Graphene oxide (GO) and its derivatives have been applied to the humidity sensing area in recent years due to its abundant hydrophilic functional groups, and proved to be ultrasensitive to the humidity changing. But the stability of the sensors is always an obstacle to their application. Besides, the long-term linearity is seldom studied. In this work, diamine modified GO (MGO) has been synthesized and mixed with Nafion polymer to form a hybrid film, and applied to the humidity sensors. We have applied two measurement methods by either fitting of the impedance spectra to extract charge transfer resistance (Rct) or measurement of the impedance under a certain frequency, to evaluate the response to the relative humidity (RH). Both MGO and its composite show good sensitivity to the RH under the two testing methods The Rct shows good linearity at the full testing RH range even after two months, while the impedance under a certain frequency can’t keep the linear response to the RH after certain period of time. The addition of Nafion decreases the Rct and increases the sensitivity of MGO based sensor. Linearity of the sensor is improved by the combination of MGO and Nafion. Long-term testing results show the linearity of the composite sensors changes over time but always keeps a better linearity than the pure MGO sensor.
TL;DR: In this paper, the authors examine water permeability through an emerging class of anion exchange membranes, hexamethyl-p-terphenyl poly (dimethylbenzimidazolium) (HMT-PMBI), and compare it against series of membrane thickness for a commercial anion-exchange membrane (AEM), Fumapem® FAA-3, and a series of proton exchange membrane, Nafion®.
TL;DR: A microneedle-based amperometric nonenzymatic glucose sensor for painless and continuous monitoring of glucose that is selective for glucose even in the presence of 10-fold higher concentrations of ascorbic acid, lactic acid, dopamine, uric Acid, and acetaminophen is reported.
Abstract: The authors report on a microneedle-based amperometric nonenzymatic glucose sensor for painless and continuous monitoring of glucose. It consists of 3 × 5 sharp stainless steel microneedles micromachined from a stainless steel substrate. The microneedles are 600 and 100 μm in height and width, respectively. Nafion and platinum black were sequentially coated onto the tip of gold-coated microneedles and used for nonenzymatic (direct) sensing of glucose. Attractive features of the modified microneedle electrode include (a) a low working potential (+0.12 V vs. Ag/AgCl), (b) a linear response in the physiologically relevant range (1–40 mM), (c) a sensitivity as high as 175 μA mM−1 cm−2, (d) a 23 μM detection limit, and (e) a response time of 2 s. The sensor also exhibits good reproducibility and stability. The sensor is selective for glucose even in the presence of 10-fold higher concentrations of ascorbic acid, lactic acid, dopamine, uric acid, and acetaminophen.