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Nafion Membranes (nafion + membrane)
Selected AbstractsInfluence of Aprotic Solvent on Selectivity of an Amperometric Sensor with Nafion MembraneELECTROANALYSIS, Issue 5 2006B. Chachulski Abstract This paper presents the results of investigation on selectivity of the sulfur dioxide amperometric sensor with Nafion membrane in the presence of carbon monoxide and nitrogen dioxide as the interferents. There have been compared selectivity coefficients, for the sensors containing the following internal electrolytes: solution of sulfuric acid (concentration 5,mol dm,3) in pure water (A) and solution of sulfuric acid (concentration 5,mol dm,3) in mixed solvent dimethylsulfoxide-water with an DMSO: H2O mole ratio of 1,:,2 (B). Values of the selectivity coefficients have been calculated based on the calibration curves. Analysis of both calibration curves and selectivity coefficients plays a significant role in optimization of a working point of a particular sensor. The investigated sensor operates in a three-electrode system, where the working and counter electrodes are vacuum sublimation deposited on the membrane surface. [source] Comparison of Electrochemical Synthesis of Ammonia by Using Sulfonated Polysulfone and Nafion Membrane with Sm1.5Sr0.5NiO4CHINESE JOURNAL OF CHEMISTRY, Issue 2 2010Ruiquan Liu Abstract Polysulfone (PSF) and sulfonated polysulfone (SPSF) were synthesized and characterized by IR spectrum. Sm1.5Sr0.5NiO4 (SSN) and Ni-Ce0.8Sm0.2O2,, (Ni-SDC, Ni-samarium doped ceria) were prepared and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Ammonia was synthesized from wet hydrogen and dry nitrogen with applied voltage, using SSN as cathode, Ni-SDC as anode, Nafion and SPSF as proton membrane respectively. The performances of Nafion and SPSF membranes in ammonia synthesis were investigated and compared at atmospheric pressure and low temperature (25,100°C). The results demonstrated that the proton conducting performances of Nafion and SPSF membranes were similar and the highest rates of evolution of ammonia were up to 1.05×10,8 and 1.03×10,8 mol·cm,2·s,1 respectively at 80°C and 2.5 V. [source] Effect of Enzyme and Cofactor Immobilization on the Response of Ethanol Oxidation in Zirconium Phosphate Modified BiosensorsELECTROANALYSIS, Issue 10 2010Mitk'El Abstract Two different self-contained ethanol amperometric biosensors incorporating layered [Ru(phend)2bpy]2+ -intercalated zirconium phosphate (ZrP) as the mediator as well as yeast -alcohol dehydrogenase (y- ADH) and its cofactor nicotinamide adenine dinucleotide (NAD+) were constructed to improve upon a design previously reported where only this mediator was immobilized in the surface of a modified electrode. In the first biosensor, a [Ru(phend)2bpy]2+ -intercalated ZrP modified carbon paste electrode (CPE) was improved by immobilizing in its surface both y- ADH and NAD+ using quaternized Nafion membrane. In the second biosensor, a glassy carbon electrode was modified with [Ru(phend)2bpy]2+ -intercalated ZrP, y- ADH, and NAD+ using Nafion as the holding matrix. Calibration plots for ethanol sensing were constructed in the presence and absence of ZrP. In the absence of ZrP in the surface of the modified glassy carbon electrode, leaching of ADH was observed as detected by UV-vis spectrophotometry. Ethanol sensing was also tested in the presence and absence of ascorbate to measure the selectivity of the sensor for ethanol. These two ethanol biosensors were compared to a previously reported one where the y -ADH and the NAD+ were in solution, not immobilized. [source] Influence of Aprotic Solvent on Selectivity of an Amperometric Sensor with Nafion MembraneELECTROANALYSIS, Issue 5 2006B. Chachulski Abstract This paper presents the results of investigation on selectivity of the sulfur dioxide amperometric sensor with Nafion membrane in the presence of carbon monoxide and nitrogen dioxide as the interferents. There have been compared selectivity coefficients, for the sensors containing the following internal electrolytes: solution of sulfuric acid (concentration 5,mol dm,3) in pure water (A) and solution of sulfuric acid (concentration 5,mol dm,3) in mixed solvent dimethylsulfoxide-water with an DMSO: H2O mole ratio of 1,:,2 (B). Values of the selectivity coefficients have been calculated based on the calibration curves. Analysis of both calibration curves and selectivity coefficients plays a significant role in optimization of a working point of a particular sensor. The investigated sensor operates in a three-electrode system, where the working and counter electrodes are vacuum sublimation deposited on the membrane surface. [source] Novel UV-induced photografting process for preparing poly(tetrafluoroethylene)-based proton-conducting membranesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2007Masaharu Asano Abstract A novel process comprising the UV-induced photografting of styrene into poly(tetrafluoroethylene) (PTFE) films and subsequent sulfonation has been developed for preparing proton-conducting membranes. Although under UV irradiation the initial radicals were mainly generated on the surface of the PTFE films by the action of photosensitizers such as xanthone and benzoyl peroxide, the graft chains were readily propagated into the PTFE films. The sulfonation of the grafted films was performed in a chlorosulfonic acid solution. Fourier transform infrared and scanning electron microscopy were used to characterize the grafted and sulfonated membranes. With a view to use in fuel cells, the proton conductivity, water uptake, and mechanical properties of the prepared membranes were measured. Even through the degree of grafting was lower than 10%, the proton conductivity in the thickness direction of the newly prepared membranes could reach a value similar to that of a Nafion membrane. In comparison with ,-ray radiation grafting, UV-induced photografting is very simple and safe and is less damaging to the membranes because significant degradation of the PTFE main chains can be avoided. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2624,2637, 2007 [source] Modification of Nafion membrane using poly(4-vinyl pyridine) for direct methanol fuel cellPOLYMER INTERNATIONAL, Issue 5 2006Jeon Chan Woong Abstract Perfluorinated membrane such as Nafion (from Du-Pont) has been used as a polymer electrolyte membrane. Nafion 117 membrane, which was usually used as the electrolyte membrane for the polymer electrolyte membrane fuel cell (PEMFC), was modified by using poly(4-vinyl pyridine) (P4VP) to reduce the methanol crossover, which cause fuel losses and lower power efficiency, by the formation of an ionic crosslink structure (sulfonic acid-pyridine complex) on the Nafion 117 surface. Nafion film was immersed in P4VP/N -methyl pyrrolidone (NMP) solution. P4VP weight percent of modified membrane was controlled by changing the concentration of P4VP/NMP solution and the dipping time. P4VP weight percent increased with increasing concentration of dipping solution and dipping time. The thickness of the P4VP layer increased with increasing concentration of dipping solution and dipping time when the concentration of the dipping solution was low. At high P4VP concentration, the thickness of the P4VP layer was almost constant owing to the formation of acid,base complex which interrupted the penetration of P4VP. FTIR results showed that P4VP could penetrate up to 30 µm of Nafion 117 membrane. Proton conductivity and methanol permeability of modified membrane were lower than those of Nafion 117. Both decreased with increasing concentration of dipping solution and dipping time. Methanol permeability was observed to be more dependent on the penetration depth of P4VP. Water uptake of the modified membrane, the important factor in a fuel cell, was lower than that of Nafion 117. Water uptake also decreased with increasing of P4VP weight. On the basis of this study, the thinner the P4VP layer on the Nafion 117 membrane, the higher was the proton conductivity. Methanol permeability decreased exponentially as a function of P4VP weight percent. Copyright © 2006 Society of Chemical Industry [source] Evaluating Enzyme Cascades for Methanol/Air Biofuel Cells Based on NAD+ -Dependent EnzymesELECTROANALYSIS, Issue 7-8 2010Abstract Previous work by the group has entailed encapsulating enzymes in polymeric micelles at bioelectrode surfaces by utilizing hydrophobically modified Nafion membranes, which are modified in order to eliminate the harsh acidity of Nafion while tailoring the size of the polymer micelles to optimize for the encapsulation of an individual enzyme. This polymer encapsulation has been shown to provide high catalytic activity and enzyme stability. In this study, we employed this encapsulation technique in developing a methanol/air biofuel cell through the combined immobilization of NAD+ -dependent alcohol dehydrogenase (ADH), aldehyde dehydrogenase (AldDH) and formate dehydrogenase (FDH) within a tetrabutylammonium bromide (TBAB) modified Nafion to oxidize methanol to carbon dioxide with poly(methylene green) acting as the NADH electrocatalyst electropolymerized on the surface of the electrode. The methanol biofuel/air cell resulted in a maximum power density of 261±7.6,,W/cm2 and current density of 845±35.5,,A/cm2. This system was characterized for the effects of degree of oxidation, temperature, pH, and concentration of fuel and NAD. [source] Investigation of the Effect of Different Glassy Carbon Materials on the Performance of Prussian Blue Based Sensors for Hydrogen PeroxideELECTROANALYSIS, Issue 3 2003Francesco Ricci Abstract Three different kinds of glassy carbon (GC-R, GC-K, GC-G) were equally pretreated, further modified with electrochemically deposited Prussian Blue and used as sensors for hydrogen peroxide at an applied potential of ,50,mV (vs. Ag|AgCl). Their performance was evaluated with respect to the following parameters: the coverage and electrochemistry of the electrodeposited Prussian Blue, the sensitivity and the lower limit of detection for hydrogen peroxide, and the operational stability of the sensors. GC-R showed the best behavior concerning the surface coverage and the operational stability of the electrodeposited Prussian Blue. For this electrode the sensitivity for hydrogen peroxide (10,,M) was 0.25,A/M cm2 and the detection limit was 0.1,,M. Scanning electron microscopy was used to study the surfaces of the three electrodes before and after the electrodeposition of Prussian Blue and to search for the reason for the three different behaviors between the different glassy carbon materials. The Prussian Blue modified GC-R was also used for the construction of a glucose biosensor based on immobilizing glucose oxidase in Nafion membranes on top of electrodeposited Prussian Blue layer. The operational stability of the glucose biosensors was studied in the flow injection mode at an applied potential of ,50,mV (vs. Ag|AgCl) and alternatively injecting standard solutions of hydrogen peroxide (10,,M) and glucose (1,mM) for 3,h. For the GC-R based biosensor a 2.8% decrease of the initial glucose response was observed. [source] Conductivity and Methanol Permeability of Nafion,Zirconium Phosphate Composite Membranes Containing High Aspect Ratio Filler Particles,FUEL CELLS, Issue 4 2009M. Casciola Abstract Gels of exfoliated ,-zirconium phosphate (ZrPexf) in dimethylformamide (DMF) were used to prepare Nafion/ZrPexf composite membranes with filler loadings up to 7,wt.-% by casting mixtures of Nafion 1100 solutions in DMF and suitable amounts of 2,wt.-% ZrP gels in DMF. TEM pictures showed that the ZrPexf particles had aspect ratio of at least 20. All samples were characterised by methanol permeability (P) and through-plane (,thp) and in-plane (,inp) conductivity measurements at 40,°C and 100% RH. The methanol permeability of Nafion membranes containing in situ grown ZrP particles with low aspect ratio (Nafion/ZrPisg) was also determined. The methanol permeability and the swelling behaviour of the composite membranes turned out to be strongly dependent on the filler morphology. As a general trend, both permeability and swelling decreased according to the sequence: Nafion/ZrPisg > Nafion > Nafion/ZrPexf. The maximum selectivity (,thp/P,=,1.4,×,105,S,cm,3,s) was found for the membrane filled with 1,wt.-% ZrPexf: this value is seven times higher than that of Nafion. For the Nafion/ZrPexf membranes, the ratio ,inp/,thp increases with the filler loading, thus indicating that the preferred orientation of the ZrP sheets is parallel to the membrane surface. [source] Synthesis of proton-conducting membranes by the utilization of preirradiation grafting and atom transfer radical polymerization techniquesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2002Svante Holmberg Abstract The atom transfer radical polymerization (ATRP) of styrene onto poly(vinylidene fluoride)- graft -poly(vinylbenzyl chloride) (PVDF- g -PVBC) membranes was investigated. Novel membranes were designed for fuel-cell applications. The benzyl chloride groups in the PVDF- g -PVBC membranes functioned as initiators, and a Cu-based catalytic system with the general formula Cu(n)Xn/ligand [where X is Cl or Br and the ligand is 2,2,-bipyridyl (bpy)] was employed for the ATRP. In addition, 10 vol % dimethylformamide was added for increased solubility of the catalyst complex in styrene. The system was homogeneous, except for the membrane, when the initiator/copper halide/ligand/monomer molar ratio was 1/1/3/500. As anticipated, the fastest polymerization rate of styrene was observed with the copper bromide/bpy-based catalyst system. The reaction rate was strongly temperature-dependent within the studied temperature interval of 100,130 °C. The degree of grafting increased linearly with time, thereby indicating first-order kinetics, regardless of the polymerization temperature. Furthermore, 120 °C was the maximum polymerization temperature that could be used in practice because the membrane structure was destroyed at higher temperatures. The degree of styrene grafting reached 400% after 3 h at 120 °C. Such a high degree of grafting could not be reached with conventional uncontrolled radiation-induced grafting methods because of termination reactions. On the basis of an Arrhenius plot, the activation energy for the homogeneous ATRP of styrene was 217 kJ/mol. The prepared membranes became proton-conducting after sulfonation of the polystyrene grafts. The highest conductivity measured for the prepared membranes was 70 mS/cm, which is comparable to the values normally measured for commercial Nafion membranes. The scanning electron microscopy/energy-dispersive X-ray results showed that the membranes had to be grafted through the matrix with both PVBC and polystyrene to become proton-conducting after sulfonation. In addition, PVDF- g -[PVBC- g -(styrene- block - tert -butyl acrylate)] membranes were also synthesized by ATRP. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 591,600, 2002; DOI 10.1002/pola.10146 [source] Pt/SiO2 as addition to multilayer SPSU/PTFE composite membrane for fuel cellsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 12 2008L. Wang Abstract A multilayer composite membrane was prepared by reinforcing sulfonated polysulfone (SPSU) with porous polytetrafluoroethylene (PTFE), and adding Pt/SiO2,Nafion® membranes on both sides of the SPSU/PTFE membrane to self-humidify and protect the inside membrane. The ex situ Fenton test and open circuit voltage (OCV) accelerated test show that the composite membrane has better stability than the initial membrane because of the protection of the outside Pt/SiO2,Nafion layers. The composite membrane has similar performance to that of NRE-212 under the fully humidified condition and better performance than NRE-212 without humidifying. The self-humidifying membrane shows great potential for use in low humidifying conditions. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||