Thermal properties and conductivity of nafionzirconia composite membrane 671 however, the membrane tends to shrink at low humidity and swells under excess water conditions due to its molecular structure. Therefore, the ionic liquidswollen transducers exhibit enhanced stability in their performance when operated for long periods of time in air. Abstract the ionic conductivity of nafion 1100 extruded membranes re. It is the first of a class of synthetic polymers with ionic properties that are called ionomers. Ionic conductivity of pemfc electrodes request pdf. Inplane ionic conductivity as a function of temperature at 90% rh for ndmpoh, ndabcooh, nmpyoh, ntmaoh and ntmp. Ionic conductivity and methanol permeability of modified nafion membranes hiroki kabumoto, h. Herein, we report the swelling behavior, ionic conductivity, and species crossover of lithiated nafion 117 membranes immersed in three nonaqueous electrolytes pc, pc. Measurements were made in 1 m h2so4 at 298 k using a fourelectrode, dc technique. Methods for swelling nafion membranes with ionic liquids are presented. Nafion s unique ionic properties are a result of incorporating perfluorovinyl ether groups terminated with sulfonate groups onto a tetrafluoroethylene backbone. One significant advantage to using ils as the proton transporting medium in the membrane is that ionic conductivity at elevated temperatures is less humiditydependent 8. Due to flexible property and light weight, the lithiated nafion membrane swollen with pc pclinafion has been employed as both solidstate electrolyte and separator to fabricate solidstate lis cells.
A textbook example of a fast ion conductor is silver iodide agi. Walsh c,z aapplied electrochemistry group, school of pharmacy and biomedical sciences, university of portsmouth, portsmouth po1 2dt, united kingdom bjohnson matthey technology center, reading rg4 9nh, united kingdom. The ionic groups form clusters of 2 4 nm in diameter, which are connected by narrow. Influence of acid pretreatment on ionic conductivity of. Microstructure evolution in nafion membranes during water uptake was investigated by positron annihilation lifetime spectroscopy, and results strongly showed that the sucnts or cnts in nafion composite membranes significantly reinforced nafion matrices, which influenced the development of ionicwater clusters in them. Due to its high ionic conductivity and chemical, mechanical, and thermal stability. The nanostructures of nafion membranes prepared by solutions casting with applying an electric field were investigated using.
Study of electrical resistance on the surface of nafion 115. Nafion is a wellknown polymeric material widely used in commercial applications, being the most common material for polymer exchange membranes pems, which can be used in both protonexchange fuel cells pemfcs and direct methanol fuel cells dmfcs due to its high ionic conductivity as well as its good mechanical, chemical and thermal. Cation exchange membrane cem anion exchange membrane aem bipolar membrane whats is the difference between cation and anion exchange membranes. But geometrical restrictions of diffusion lead to a decreasing preexponential factor, i. Enhancement in proton conductivity and thermal stability in. Fenton university of connecticut, chemical engineering, storrs, ct 06269 usa visiting engineer from sanyo electric co.
Parekha,b,1,2 adepartment of molecular spectroscopy, max planck institute for polymer research, d55128 mainz, germany. A method for improving ionic conductivity of nafion membranes. Effects of curing condition of solution cast nafion. Determination of pore size distribution of nafionsulfated. In order to reduce the methanol permeability of the nafion membranes while minimizing the loss of proton conductivity, we add sulfated. Also, techniques for plating the ionic liquidswollen. Lithiated nafion as polymer electrolyte for solidstate. Anion exchange membranes derived from nafion precursor for the alkaline fuel cell a thesis. Nafion has been reported to be based mainly on two cases. For more than 50 years, nafion membranes and dispersions have provided critical applications with unparalleled performance and durability. A method for improving ionic conductivity of nafion membranes and. The proton conductivity of a series of extruded nafion membranes of equivalent weight ew of 1100 and nominal dry thickness of 51, 89, 127, and 178. The article presents an overview on nafion membranes highlighting their merits and.
Effort have been made to make membrane other than nafion. Nafion is a polymer with ionic conductivity, and it is used in multigas analyzers in anesthesia, where the special high permeability to water is useful. The ionic conductivity of a nafion 1100 series of protonexchange membranes recast from butan1ol and propan2ol. The glass transition temperature of nafion limits the upper temperature ranges to about 100c. Highly sulfonated diamine synthesized polyimides and protic. Upon this treatment, the ionic liquids cations partially replace the protons of the sulfonic acid groups in. The measurement of ionic conductivity is crucially important in order to evaluate the. The ionic conductivity of the most frequently used nafion membrane,, is determined by temperature and water content, i. In this paper, we show that proton conductivity and pemfc performance of nafion membranes prepared by solutions casting can be improved by aligning the side cahin ionic aggregations along the membrane thickness direction using an electric field.
Ionic conductivity of the cast membranes was higher than that of commercial nafion 112 membrane since welldefined % water uptake w w1. Microstructure evolution in nafion membranes during water uptake was investigated by positron annihilation lifetime spectroscopy, and results strongly showed that the sucnts or cnts in nafion composite membranes significantly reinforced nafion matrices, which influenced the development of ionic water clusters in them. Structural morphology and electronic conductivity of. The lithium polymer electrolyte after gelling with a plasticizer shows a high ionic conductivity of 3. Pdf the effect of membrane thickness on the conductivity of. A the open diode, where cations access the microhole via nafion with a resulting high conductivity and some accumulation of salt in the adjacent solution phase. Ionic conductivity of an extruded nafion 1100 ew series of membranes. The nafion117 membranes gave conductivity at 30 c and 60 c of 0.
Connecticut ave, southern pines, north carolina, usa 28387 ionic transport resistance is a key performance property of polymer electrolyte membranes pems and can be determined for transport. In this study, our goal was to extend the particle size study of nafion nanocomposites with surface sulfonated. Ionic conduction ionic conduction is caused by the movement of some negatively or positively charged ions which hop from lattice site to lattice site under the influence of an electric field. Finite thickness effects on nafion water uptake and ionic. Differences in water sorption and proton conductivity between nafion and speek xuemei wu,1 xiaowen wang,2 gaohong he,1 jay benziger3 1state key laboratory of fine chemicals and development center of membrane science and technology. Enhanced proton conductivity of nafion hybrid membrane under. The ionic conductivity of a nafion 1100 series of proton.
Ionic conductivity of an extruded nafion 1100 ew series of. View enhanced pdf access article on wiley online library html view. Improving the conductivity of sulfonated polyimides as. Irreversibility of proton conductivity of nafion and nafiontitania composites at high relative humidity, materials for renewable and sustainable energy, 2015, pp. Structureproperty relationships at nafion thinfilm. The proton conductivity of a series of extruded na. The water uptake in the lamellae and the bulklike layer varies nonmonotonically, decreasing as the equivalent nafion thickness increases from 7 nm to 12 nm, increasing with increasing film thickness for equivalent nafion thicknesses ranging from 12 nm60 nm, and then constant for films with equivalent thickness. Upon this treatment, the ionic liquids cations partially replace the protons of the sulfonic acid groups in nafion. Irreversibility of proton conductivity of nafion and. Correlated interfacial water transport and proton conductivity in perfluorosulfonic acid membranes xiao linga, mischa bonna, katrin f. In this paper, we show that proton conductivity and pemfc performance of nafion membranes prepared by solutions casting can be improved by aligning the side.
Enhancement in proton conductivity and thermal stability. Cation exchange membranes cem are usually comprised of a fluorinated polymer with sulfonic acid sites and have excellent ionic conductivity and thermalchemical durability. Highly sulfonated diamine synthesized polyimides and. A study of the effect of heattreatment on the morphology. Proton conductivity of nafionexsitu sulfonic acidmodified. Thermal properties and conductivity of nafion zirconia composite membrane 671 however, the membrane tends to shrink at low humidity and swells under excess water conditions due to its molecular structure. The nanostructures of nafion membranes prepared by solutions casting with applying an electric field were investigated using transmission electron. Properties of the nafion membrane impregnated with. B the closed diode where cations access the microhole from the opposite solution phase, where lower.
Ionic conductivity values were also determined for the membranes and are given in table 2. Dec 28, 2007 the modified membranes were characterized in terms of uptake behavior, washing out of the ionic liquids by water, swelling in humidified environment, thermal stability, mechanical properties, ion exchange capacity and ion conductivity. Modeling of ion conductivity in nafion membranes springerlink. An investigation of the ionic conductivity and species. Conductive behavior in relation to domain morphology and phase. In charge of major work iowa state university ames, iowa 1973. Improving the conductivity of sulfonated polyimides as proton.
Figure 3 proton conductivity of the membranes measured by two electrode method proton conductivity of nafion membrane in actual direct methanol. In this study, we report the ionic cluster size distribution of nafionbased membranes, which are determined using nmr cryoporometry. During pretreatment, the type of protondonating acid, the acid concentration as well as the applied temperature governs the ionic conductivity. Anion exchange membranes derived from nafion precursor for the alkaline fuel cell a thesis submitted to the faculty of drexel university by holly lynn schaeffer salerno. Obviously, the ionic conductivity strongly depends on the amount of protonated sulfonic groups in nafion. The electrochemical measurements of pclinafion membrane show that its liion transference number is 0. Pdf ionic conductivity of an extruded nafion 1100 ew series of. Ionic conductivity and methanol permeability of modified.
Differences in water sorption and proton conductivity between. Jiangyu li and siavouche nematnasser micromechanical analysis of ionic clustering in nafion. Modification of nafion membranes by impregnation with ionic. Hpfgnmr diffusion and proton conductivity data for nafion 117 is presented as a function of temperature and water content. Nafion1 is the stateoftheart polymer electrolyte material for a range of. Measurements were made in 1 m h 2 so 4 at 298 k using a fourelectrode, dc. Ionic diode characteristics at a polymer of intrinsic. In 1973, liang10 reported enhancement of ionic conductivity by several orders of. Electronion and proton conductivities of the 6040 nafionpvdftrfe blend were discussed in relation to the. Furthermore, the applied pretreatment procedure strongly influences the water content and hence the resulting ionic conductivity of the membrane.
By virtue of its outstanding proton conductivity 1,2, nafion is currently regarded as the benchmarked polymer electrolyte membrane pem. Direct laser writing of microsupercapacitors on hydrated. While the ionic liquids act as potent plasticizers in the polymer matrix, thermal stability of these systems. Enhanced proton conductivity of nafion hybrid membrane. The electrical conductivity of the solid increases by 4000x. An expression was derived for ionic conductivity incorporating the influence of surface resistance. Nafion, developed by dupont, is the most frequently used pem in fuel cell applications 39.
Anion exchange membranes derived from nafion precursor for the alkaline. Previous studies of nafion composites with silica particles without surface modification did show that composites with smaller silica particles exhibited superior ionic conductivity and water retention at higher temperatures 4,5,21. From this, h 2 o diffusion on a molecular scale is concluded to be similar to the one in bulk water. We report here the thickness dependence of water uptake, interfacial ionic domain structure, and anisotropic ionic conductivity in ultrathin nafion films 5153 nm on sio 2. Properties of the nafion membrane impregnated with hydroxyl. Pdf the effect of membrane thickness on the conductivity. Modification of nafion membranes by impregnation with.
The effect of nafion loading in the cathode catalyst layer of proton exchange membrane fuel cell pemfc electrodes was studied by impedance spectroscopy, cyclic voltammetry, and polarization experiments. Nafion and modifiednafion membranes for polymer electrolyte fuel. Our results show that solvent volume fraction within the membrane has the greatest effect on both conductivity and crossover. All three heattreated membranes had slightly higher. A facecentered cubic fcc lattice model for a spatial cluster distribution was used to modify the effect of water content on ionic conductivity in the polymeric matrix, i. Characterizing throughplane and inplane ionic conductivity. Pdf the ionic conductivity of a nafion 1100 series of. Characterizing throughplane and inplane ionic conductivity of polymer electrolyte membranes kevin r. A single ionic conductor based on nafion and its electrochemical properties used as lithium polymer electrolyte the journal of physical chemistry b acs publications. The useful operating temperature is closer to 80c because the membrane loses water and thus ionic conductivity at high temperature. The combination of high values for temperature, relative humidity and contact pressure leads to enhanced ionic conductivity of nafion membranes with a maximum value of 85. Anion exchange membranes derived from nafion precursor for. Therefore, the pk a value of the applied acid during pretreatment is a key parameter for a high ionic conductivity in the resulting pretreated membrane. Micromechanical analysis of ionic clustering in nafion.
Nafions unique ionic properties are a result of incorporating perfluorovinyl ether groups terminated with sulfonate groups onto a tetrafluoroethylene backbone. Electromechanical transduction in ionic liquidswollen. The chemical structure of nafion is illustrated in fig. Nafion 112 and nr212 nonsupported pem goreselect supported pem throughplane membrane test system. A theoretical investigation was conducted to describe the ion transport behavior in a nafion membrane of proton exchange membrane fuel cells pemfc. The new mentioned membrane is prepared by constructing supramolecular structure arise from. Role of thickness and density on the ionic conductivity of fuel cell. Pils have even higher ionic conductivity than common ils which are usually aprotic, and most importantly, pils are desired due to their intrinsic proton conductivity. In the present contribution we investigated the influence of the acid pretreatment procedure of nafion 117 membranes on the resulting ionic conductivity by using electrochemical impedance.
Proton conductivity of nafion membrane in actual direct. Upon heating the solid to 146 c, this material adopts the alphapolymorph. Effects of curing temperature on ionic conductivity and water uptake of the cast membranes membrane curing temperature oc ionic conductivity scm water uptake %. The composite membrane of nafion with ionic liquids has potential to be used in ionic devices at increased temperatures, especially acetates. A method for improving ionic conductivity of nafion. All ionic liquids increased the thermal stability of nafion membrane approximately by 50. Incorporation of hyperbranched supramolecules into nafion ionic. The membrane area resistance increases with thickness, as expected, from 0. The ionexchange capacity iec, which expresses the amount of exchangeable protons, was. May 31, 2006 in this paper, we show that proton conductivity and pemfc performance of nafion membranes prepared by solutions casting can be improved by aligning the side cahin ionic aggregations along the membrane thickness direction using an electric field. Today, the nafion portfolio provides leadingedge solutions that create production and process improvements, ensure superior performance standards, and allow manufacturers to pursue new markets. The effect of cluster morphology on the effective electroelastic moduli and the effective ionic conductivity is then studied by a micromechanical multiinclusion model.
1230 1378 1387 1115 1205 736 709 309 182 1376 523 1404 1043 1179 458 629 129 1406 1110 1255 840 681 1316 364 47 898 645 1011 895 1491 1400 529 56 1246 494 568 674 262 213 462 822 1428 257 1026 190 362 255 415 1452 1352 1441