Showing papers on "Nafion published in 1995"
TL;DR: In this paper, the conductance of Nafion membranes was investigated by means of impedance spectroscopy as a function of temperature and sample treatment, and an Arrhenius-type analysis showed two regimes, with a change in activation energy observed at transition temperatures between 225 and 260 K which depends on the water content.
277 citations
238 citations
TL;DR: In this paper, an analysis is made of the performances of PEMFCs with Dupont's Nafion, Dow's experimental, and Asahi Chemical's Aciplex-S® membranes.
168 citations
TL;DR: In this paper, it was found that glucose oxidase or D-amino oxidase can be incorporated into a Prussian blue film during its electrochemical growth process, and two amperometric biosensors were fabricated by electrochemical codeposition, and the resulting sensors were protected by a thin film of Nafion.
166 citations
152 citations
TL;DR: In this article, the water transport behavior in Nafion 117 cation exchange membrane was studied using the streaming potential method, and the water transference coefficient of the membranes in the H{sup +} form was found to be 2.6.
Abstract: The water transport behavior in Nafion 117 cation exchange membrane was studied using the streaming potential method. The water transference coefficient of the membranes in the H{sup +} form was found to be 2.6. The results also show that Nafion 117 membranes have a good cation selectivity performance in HCl solutions within a concentration range between 0.003 and 1N. The water transference coefficients of the membranes equilibrated with alkali metal chlorides and alkaline earth metal chlorides solutions were investigated as well. It was found that the water transport behavior is related to the surface-charge density, hydration enthalpy of the cations exchanged in the membranes, and water content of the membrane. The effect diameter of the micropore in Nafion 117 was estimated as 0.8 to 1.3 nm.
143 citations
TL;DR: In this paper, the influence of Nafion thickness on electrocatalytic properties for H2 oxidation and O2 reduction was investigated to predict an ideal structure of catalyst layer for PEFCs.
129 citations
97 citations
TL;DR: In this article, the electrochemical behavior of glucose at Pt electrodes was investigated in alkaline solutions using cyclic voltammetry and the modulated potential-time waveform (MPTW) technique.
88 citations
TL;DR: In this paper, a series of differently cross-linked FEP-g-polystyrene proton exchange membranes has been synthesized by the pre-radiation grafting method [FEP: poly(tetrafluoroethylene-co-hexafluoropropylene)].
Abstract: A series of differently cross-linked FEP-g-polystyrene proton exchange membranes has been synthesized by the preirradiation grafting method [FEP: poly(tetrafluoroethylene-co-hexafluoropropylene)]. Divinylbenzene (DVB) and/or triallyl cyanurate (TAC) were used as cross-linkers in the membranes. It was found that the physical properties of the membranes, such as water-uptake and specific resistance, are strongly influenced by the nature of the cross-linker. Generally it can be stated that DVB decreases water-uptake and increases specific resistance; on the other hand TAC increases swelling and decreases specific resistance to values as low as 5.0 {Omega} cm at 60 C. The membranes were tested in H{sub 2}/O{sub 2} fuel cells for stability and performance. It was found that thick (170 {micro}m) DVB cross-linked membranes showed stable operation for 1,400 h at temperatures up to 80 C. The highest power density in the fuel cell was found for the DVB and TAC double-cross-linked membrane; it exceeded the value of a cell with a Nafion{reg_sign} 117 membrane by more than 60%.
88 citations
TL;DR: In this article, transmission electron microscopy (TEM) and transmission electron diffraction were used to study the microstructure of recast Nafion films, and the results showed a nonrandom distribution of the -SOsgroups in the polymer film, primarily as -5 nm clusters.
Abstract: Transmission electron microscopy (TEM) and transmission electron diffraction were used to study the microstructure of recast Nafion films. Zero-loss bright-field (BF) images were obtained, as well as Dage SIT low-light images (minimum specimen damage) and specific sulfur imaging. The results show a nonrandom distribution of the -SOsgroups in the polymer film, primarily as -5 nm clusters. Electron diffraction of deposited Nafion films shows the existence of single crystals, randomly distributed in the film, with an average distance of several microns. The diffraction pattern indicates an orthorhombic crystal structure which is similar to that of polyethylene (PE). The calculated d-spacings of the corresponding lattice planes for the two polymers are also quite close, suggesting similarity in their crystal structures. This result indicates that the fluorocarbon backbone of Nafion is in the form of a linear zigzag chain as in PE and not a twisted chain as in polytetrafluoroethylene (PTFE), despite the
TL;DR: In this article, the facilitation effect of CO sub 2 facilitated transport was studied using a membrane with amine sites covalently bound to the polymer backbone and ion exchange membranes which have amine complexing agents (carrier) as counterions.
Abstract: CO{sub 2} facilitated transport was studied using a membrane with amine sites covalently bound to the polymer backbone and ion exchange membranes which have amine complexing agents (carrier) as counterions. The two types of membranes were compared, and several amine functionalities for the ion-exchange membrane were studied. Although the covalently bonded membranes had a larger absorption capacity than amine functionalized Nafion ion-exchange membranes, the facilitation effect of CO{sub 2} through the covalently bonded membrane was very small (less than 1.5 at 10 kPa CO{sub 2} partial pressure) compared with the ion-exchange membrane (8.0 at 11 kPa CO{sub 2} pressure with mono protonated ethylenediamine carrier form in Nafion 117). A simulation model for the covalently bound membranes was developed to understand the results. The facilitation effect depends largely on carrier diffusivity, and reactive diffusion through the covalently bonded membrane is much slower than counterion diffusivity through the ion-exchange membrane. The ethylenediamine carrier exhibited a large facilitation effect in a Nafion 117 membrane. Other secondary or hindered diamines exhibited a small facilitation effect. For a swollen Nafion membrane, both ethylenediamine and ethylenediamine derivatives showed a high facilitation effect, and a secondary diamine produced a facilitation factor of 4.09 and a CO{sub 2}more » flux of 1.02 {times} 10{sup {minus}8} mol/cm{sup 2} at 22.5 kPa CO{sub 2} pressure in the feed.« less
TL;DR: In this paper, the preparation of Cu-solid polymer electrolyte ( spe ) composite electrodes for gas-phase electrochemical reduction of CO 2 was studied by electroless plating methods.
TL;DR: In this paper, the PPy/Nafion electrode was investigated in a polyethylene oxide (PEO)-LiClO{sub 4} electrolyte and the results of the impedance spectroscopy and potential-step chronoamperometry confirmed that the improvement in the redox reaction of the polypyrrole (PPy/nafion) film was due to the enhancement of the ion diffusion rate in the film.
Abstract: Nafion{reg_sign} was introduced into a polypyrrole (PPy) matrix, and the redox performance of the PPy/Nafion electrode was investigated in a polyethylene oxide (PEO)-LiClO{sub 4} electrolyte. A rougher interface between polymer cathode and polymer electrolyte is usually needed for an all-solid battery, however, the PPy/Nafion cathode works well regardless of the flat surface of the PPy/Nafion film. When compared to a PPy film doped with ClO{sub 4}{sup {minus}} anions with a similar morphology, the PPy/Nafion film showed better redox performance. The results of the impedance spectroscopy and potential-step chronoamperometry confirmed that the improvement in the redox reaction of the PPy/Nafion film was due to the enhancement of the ion diffusion rate in the film. Thus, the PPy/Nafion film showed good charging-discharging properties in a rechargeable Li/PEO-LiClO{sub 4}/(PPy/Nafion) battery.
TL;DR: It was confirmed that the Nafion coating prevents interference by anionic substances such as ascorbic acid and uric acid, and decreases acetaminophen interference.
TL;DR: In this paper, a new fabrication method for a Nafion joint for capillary eletrophoresis with on-column eletrochemical detection (CEEC) is described.
Abstract: A new fabrication method for a Nafion joint for capillary eletrophoresis with on-column eletrochemical detection (CEEC) is described. The Nafion joint was cast directly on the capillary column. A tungsten wire was used to define the flow channel during fabrication and removed for operation. This method allowed the construcction ofNafion joints over 1 mm in length, which did not significantly contribute to band broadening. The increased length of these joints resulted in a significant decrease in the noise at the electrochemical detector. The relation-ship between the noise, the magnitude of the electrophoresis current, and the length of the Nafion joint was investigated. The separation efficiency of a CEEC system equipped with this type of Nafion joint was investigated using hydroquinone, phenolic acids, and catecholamines. Using 10 mM phosphate buffer at pH 6.1 for the run buffer, the Nafion joint did not have a significant effect on the separation efficiency of neutral or acidic compounds; however, the cationic compounds exhibited significant band broadening. The interaction of cations with the Nafion was minimized by use of a 100 mM EPPS zwitterion, pH 6.0, running buffer. A detection limit of 5×10 -10 M was achieved for hydroquinone and 2×10 -9 M for the phenolic acids using the phosphate running buffer. A slightly higher detection limit of 5×10 -9 M was achieved for the catecholamines using the EPPS running buffer
TL;DR: In this paper, a new arrangement of a polymer electrolyte membrane fuel cell (PEMFC) support is proposed, which allows the operation of a 100 cm2 surface area fuel cell with cold and unhumidified gases.
TL;DR: In this article, a Nafion/ruthenium oxide pyrochlore (Pb 2 Ru 2-x Pb x O 7-y )-modified glassy carbon electrode exhibits excellent electrocatalytic activity in the oxidation of hydrazine in neutral media.
Abstract: A Nafion/ruthenium oxide pyrochlore (Pb 2 Ru 2-x Pb x O 7-y )-modified glassy carbon electrode exhibits excellent electrocatalytic activity in the oxidation of hydrazine in neutral media. The catalyst is synthesized directly inside the Nafion thin film matrix, which is spin coated onto a glassy carbon electrode. Hydrazine is detected by flow injection analysis at the modified electrode with excellent sensitivity. Linear calibration curves are obtained over the 5×10 -5 -6×10 -7 M range with pH 8.0 ammonia-ammonium chloride buffer solution as the carrier. The detection limit is 0.048 ng. The practical analytical utility is illustrated by selective flow injection measurements of hydrazine in the presence of oxalic acid and surface-active materials
TL;DR: Porous Nafion-PTFE-bonded gas-diffusion electrodes (GDEs) for use in (PEFC) were prepared by a cold rolling process as discussed by the authors.
TL;DR: In this paper, glucose oxidase was immobilized onto electrodes by co-deposition from an aqueous solution containing the diluted ion-exchange polymer Nafion, which was used to provide high local concentrations of l,1'-dimethylferricinium (DMFc+) mediator in the film by exchange from solution.
TL;DR: In this paper, Nafion® 117-doped polyaniline films were prepared by two chemical methods, and the preparation procedures were very similar, differing only in the timing of the doping step, i.e. before or after film preparation.
TL;DR: In this paper, an amperometric sensor utilizing tetrathiafulvalene (TTF) as an electron shuttle between immobilized lactate oxidase and a glassy carbon electrode is described.
TL;DR: In this paper, the charge transfer between Ru(bpy) 2+3 (where bpy is 2,2′-bipyridine) complexes incorporated into a Nafion® membrane has been investigated using in situ spectrocyclic voltammetry and statistical calculation of the intermolecular distance between the complexes.
TL;DR: In this paper, the changes in the resistance of a Nation ® membrane during the process in which one equilibrium water content changes into another owing to exchange of water between Nafion ® and ambient air of a certain relative humidity (RH).
TL;DR: Results showed that clenbuterol undergoes an ECE process, and this compound is irreversibly oxidised at high potentials, resulting in the formation of a product which demonstrates quasi-reversible electrochemical behaviour at less positive potentials.
TL;DR: In this paper, a theoretical model is developed to describe the impedance of two electrolyte solutions separated by a fixed-site ion exchange membrane, which is the sum of the solution and membrane impedances, each of which splits into a resistance and a Warburg impedance owing to the diffusion ion transport in the solution.
TL;DR: In this article, 1H and 31P NMR spectroscopic measurements were used to examine the behavior of H3PO4 sorbed in Nafion® 117 membranes.
TL;DR: In this article, four polymer-modified mercury film electrodes (MFEs) on a glassy carbon substrate were tested for their ability to determine lead and cadmium in the presence of surfactants.
Abstract: Four different polymer-modified mercury film electrodes (MFEs) on a glassy carbon substrate were tested for their ability to determine lead and cadmium in the presence of surfactants. The polymers used for electrode modification were: Nafion, polyaniline, base-hydrolyzed cellulose acetate, and base-hydrolyzed poly(ethyl 3-thiophene acetate). Triton X-100, sodium dodecyl sulfate, dodecyl pyridinium chloride, and bovine serum albumin were chosen as representatives of surface active compounds. It is shown that polymer-covered electrodes are useful in surfactant-containing media in some instances, but none of them remained unaffected by any of the four surfactants. The cellulose acetate electrodes seem to be less affected by proteins than the bare MFE and other modified electrodes. The Nafion and cellulose acetate-coated electrodes were used for the determination of lead in filtered and acidified, but otherwise untreated, water samples from a sewage treatment plant. The results obtained with the cellulose acetate-coated electrode were in good agreement with those from atomic absorption spectroscopy.
TL;DR: Overlaying the sensors with a Nafion coating considerably improved the sensor selectivity for dopamine by effectively precluding neutral and anionic solutes from entering the biofilm thus removing the interference of most of the 23 solutes examined in this study.