Showing papers on "Nafion published in 2012"
TL;DR: This study demonstrated that inexpensive, highly reproducible, high performance and scalable air-cathode can be produced by rolling method without using noble metal and expensive binder.
394 citations
TL;DR: Recent progress is reported in the development of advanced APEs, which are highly resistant to swelling and show conductivities comparable with Nafion at typical temperatures for fuel-cell operation.
Abstract: Although the polymer electrolyte fuel cell (PEFC) is a superior power source for electric vehicles, the high cost of this technology has served as the primary barrier to the large-scale commercialization. Over the last decade, researchers have pursued lower-cost next-generation materials for fuel cells, and alkaline polymer electrolytes (APEs) have emerged as an enabling material for platinum-free fuel cells.To fulfill the requirements of fuel cell applications, the APE must be as conductive and stable as its acidic counterpart, such as Nafion. This benchmark has proved challenging for APEs because the conductivity of OH– is intrinsically lower than that of H+, and the stability of the cationic functional group in APEs, typically quaternary ammonia (−NR3+), is usually lower than that of the sulfonic functional group (−SO3–) in acidic polymer electrolytes.To improve the ionic conductivity, APEs are often designed to be of high ion-exchange capacity (IEC). This modification has caused unfavorable changes in...
345 citations
TL;DR: Of great interest is the fact that the compound exhibits high proton conductivity with a low activation energy that is comparable to those of Nafion presently used in fuel cells.
Abstract: A novel metal–organic framework, [{(Zn0.25)8(O)}Zn6(L)12(H2O)29(DMF)69(NO3)2]n (1) {H2L = 1,3-bis(4-carboxyphenyl)imidazolium}, has been synthesized under solvothermal conditions in good yield. It shows a Zn8O cluster that is coordinated to six ligands and forms an overall three-dimensional structure with channels along the crystallographic a and b axes. The imidazolium groups of the ligand moiety are aligned in the channels. The channels are not empty but are occupied by a large number of DMF and water molecules. Upon heating, these solvent molecules can be removed without breakdown of the overall structure of the framework as shown by variable-temperature powder X-ray diffraction patterns. Of great interest is the fact that the compound exhibits high proton conductivity with a low activation energy that is comparable to those of Nafion presently used in fuel cells.
246 citations
TL;DR: In this article, the Li-ion transference number and the elemental sulfur permeability of the ionomer electrolyte showed the polysulfide anions can transport through the Nafion ionomer film hardly.
239 citations
TL;DR: An implantable fuel cell that generates power through glucose oxidation, producing steady-state power and up to peak power is developed, demonstrating computationally that the natural recirculation of cerebrospinal fluid around the human brain theoretically permits glucose energy harvesting at a rate on the order of at least 1 mW with no adverse physiologic effects.
Abstract: We have developed an implantable fuel cell that generates power through glucose oxidation, producing steady-state power and up to peak power. The fuel cell is manufactured using a novel approach, employing semiconductor fabrication techniques, and is therefore well suited for manufacture together with integrated circuits on a single silicon wafer. Thus, it can help enable implantable microelectronic systems with long-lifetime power sources that harvest energy from their surrounds. The fuel reactions are mediated by robust, solid state catalysts. Glucose is oxidized at the nanostructured surface of an activated platinum anode. Oxygen is reduced to water at the surface of a self-assembled network of single-walled carbon nanotubes, embedded in a Nafion film that forms the cathode and is exposed to the biological environment. The catalytic electrodes are separated by a Nafion membrane. The availability of fuel cell reactants, oxygen and glucose, only as a mixture in the physiologic environment, has traditionally posed a design challenge: Net current production requires oxidation and reduction to occur separately and selectively at the anode and cathode, respectively, to prevent electrochemical short circuits. Our fuel cell is configured in a half-open geometry that shields the anode while exposing the cathode, resulting in an oxygen gradient that strongly favors oxygen reduction at the cathode. Glucose reaches the shielded anode by diffusing through the nanotube mesh, which does not catalyze glucose oxidation, and the Nafion layers, which are permeable to small neutral and cationic species. We demonstrate computationally that the natural recirculation of cerebrospinal fluid around the human brain theoretically permits glucose energy harvesting at a rate on the order of at least 1 mW with no adverse physiologic effects. Low-power brain–machine interfaces can thus potentially benefit from having their implanted units powered or recharged by glucose fuel cells.
225 citations
TL;DR: In this article, the potentialities of PEEK-based polymers are discussed, pointing out the main benefits and drawbacks of these proton exchange membranes for fuel cell applications, and the use of sulfonated PEEK with cardo-group (PEEK-WC) is particularly stressed.
212 citations
TL;DR: In this article, the authors focus mainly on the techniques of silicate-based nanocomposite fabrication and the resulting impact on the membrane properties, including the degree of dispersion and interaction between the organic polymer and inorganic silicates.
183 citations
TL;DR: In this article, the authors studied the structure, swelling, water solubility, and water transport kinetics as a function of relative humidity for confined polyelectrolyte films thinner than 222 nm.
Abstract: Fuel cells based on polymer electrolyte membranes (PEM) show promise as a means of energy conversion for a wide range of applications both in the transportation sector and for stationary power production due to their high charge density and low operating temperatures. While the structure and transport of bulk PEMs for fuel cell applications have been studied extensively, much less is known about these materials at interfaces and under confinement, conditions that are highly relevant in the membrane electrode assembly of a working PEM fuel cell. Using X-ray reflectivity, neutron reflectivity, grazing-incidence small-angle X-ray scattering, quartz crystal microbalance, and polarization-modulation infrared reflection–absorption spectroscopy, we have studied the structure, swelling, water solubility, and water transport kinetics as a function of relative humidity for confined polyelectrolyte films thinner than 222 nm. While the humidity-dependent equilibrium swelling ratio, volumetric water fraction, and effe...
165 citations
TL;DR: In this paper, an ionic conductive Nafion/graphene oxide (GO) composite membrane for application in direct methanol fuel cells is presented. But, the authors do not consider the use of GO nanofillers.
151 citations
TL;DR: In this paper, a new generation of nanocomposite membrane and its efficiencies were compared with Nafion 117 in a dual-chamber microbial fuel cell (MFC).
142 citations
TL;DR: In this paper, the flux of liquid water through Nafion membranes of different thickness and equivalent weight was measured as a function of hydrostatic pressure and temperature, and the pore network structure from water sorption and hydraulic permeability were consistent with the spacing between hydrophilic domains observed with small angle X-ray scattering experiments.
TL;DR: In this article, a thin Nafion layer on Pd-deposited TiO2 nanoparticles was introduced to enhance the photosynthetic conversion of CO2 to hydrocarbons in an aqueous suspension (without any sacrificial electron donor) under UV and solar irradiation conditions.
Abstract: Introducing a thin Nafion layer on Pd-deposited TiO2 nanoparticles markedly enhances the photosynthetic conversion of CO2 to hydrocarbons (mainly methane and ethane) in an aqueous suspension (without any sacrificial electron donor) under UV and solar irradiation conditions.
TL;DR: The morphology of Nafion (EW = 1000, Na+ form) in dilute solvents was investigated using small angle neutron scattering (SANS) and 19F NMR as mentioned in this paper.
Abstract: The morphology of Nafion (EW = 1000, Na+ form) in dilute solvents is investigated using small angle neutron scattering (SANS) and 19F NMR. SANS modeling indicates three types of particle morphology: (i) a well-defined cylindrical dispersion in glycerol and in ethylene glycol with different degrees of solvent penetration; (ii) a less-defined, highly solvated large particle (>200 nm) in water/isopropanol mixtures; and (iii) a random-coil conformation (true solution behavior) in N-methylpyrrolidone. These distinct morphological characteristics of Nafion are consistent with the main and side chain mobilities measured by 19F NMR.
TL;DR: In this article, self-made carbon nanofiber (CNF)/Nafion and activated carbon-nanofiber-naphion nanocomposite membranes are fabricated and tested in a microbial fuel cell.
TL;DR: The hybrid membranes are characterized by a combination of analytical techniques, which show that highly homogeneous exfoliated nanocomposites are created and can withstand higher temperatures than pure Nafion.
Abstract: Novel nanostructured organo-modified layered materials based on graphene oxide carrying various hydrophilic functional groups (-NH(2), -OH, -SO(3)H) are prepared and tested as nanofillers for the creation of innovative graphene-based Nafion nanocomposites. The hybrid membranes are characterized by a combination of analytical techniques, which show that highly homogeneous exfoliated nanocomposites are created. The pulsed field gradient NMR technique is used to measure the water self-diffusion coefficients. Remarkable behavior at temperatures up to 140 °C is observed for some composite membranes, thereby verifying the exceptional water retention property of these materials. Dynamic mechanical analysis shows that hybrid membranes are much stiffer and can withstand higher temperatures than pure Nafion.
TL;DR: In this paper, graphite oxide (GO)/Nafion composite membranes were prepared and used for polymer electrolyte membrane fuel cells (PEMFCs), which were characterized by transmission electron microscopy.
Abstract: Graphite oxide (GO)/Nafion composite membranes were prepared and used for polymer electrolyte membrane fuel cells (PEMFCs). Membranes were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) which showed the distribution of graphite oxide sheets in a Nafion polymer matrix. Fourier transform infrared spectroscopy data (FTIR) for Nafion and GO showed vibrations at 3440 cm−1 which was attributed to intermolecular hydrogen bonding and at 1724 cm−1 ascribed to the CO stretching frequency. The proton conductivities of GO (4 wt%)/Nafion composite, Nafion 212 and Nafion recast membranes at 30 °C and 100% humidity were 0.078, 0.068 and 0.043 S cm−1 respectively. The fuel cell performance of the GO (4 wt%)/Nafion composite membrane gave a maximum power density of 415 mW cm−2 at 0.390 V at 60 °C. At 100 °C a GO (4 wt%)/Nafion membrane fuel cell performance of 212 mW cm−2 was obtained which was much better than those of Nafion recast and Nafion 212 under 25% relative humidity.
TL;DR: In this paper, a polyvinyl alcohol/chitosan, PCS, blended membrane is prepared by direct blend process and solution casting method, in order to reduce the swelling ratio and enhance the chemical and thermal stabilities of the PCS.
TL;DR: In this article, the glass transition temperature (Tg) of the Nafion 117 membrane was traced by DSC step by step during the preparation of the membrane electrode assembly (MEA).
TL;DR: Using in situ grazing-incidence small-angle X-ray scattering (GISAXS) techniques, the authors demonstrates that the wetting interaction in thin-film interfaces can drastically affect the internal morphology of ionomers and in turn modify its transport properties.
Abstract: Proton conducting ionomers are widely used for electrochemical applications including fuel-cell devices, flow batteries, and solar-fuels generators. For most applications the presence of interfacial interactions can affect the structure and properties of ionomers. Nafion is the most widely used ionomer for electrochemical applications due to their remarkable proton conductivity and stability. While Nafion membranes have been widely studied, the behavior and morphology of this ionomer under operating conditions when confined to a thin-film morphology are still not well understood. Using in situ grazing-incidence small-angle X-ray scattering (GISAXS) techniques, this work demonstrates that the wetting interaction in thin-film interfaces can drastically affect the internal morphology of ionomers and in turn modify its transport properties. Thin films cast on hydrophobic substrates result in parallel orientation of ionomer channels that retard the absorption of water from humidified environments; while films ...
TL;DR: In this article, custom-made proton exchange membranes (PEM) are synthesized by incorporating sulfonated poly(ether ether ketone) (SPEEK) in poly (ether sulfone), for electricity generation in microbial fuel cells (MFCs).
TL;DR: In this paper, small-angle X-ray scattering (SAXS) experiments captured the rapid swelling of the Nafion membrane in liquid water with a nanostructure rearrangement on the order of seconds.
Abstract: The ability of the Nafion membrane to absorb water rapidly and create a network of hydrated interconnected water domains provides this material with an unmatched ability to conduct ions through a chemically and mechanically robust membrane. The morphology and composition of these hydrated membranes significantly affects their transport properties and performance. This work demonstrates that differences in interfacial interactions between the membranes exposed to vapor or liquid water can cause significant changes in kinetics of water uptake. In situ small-angle X-ray scattering (SAXS) experiments captured the rapid swelling of the membrane in liquid water with a nanostructure rearrangement on the order of seconds. For membranes in contact with water vapor, morphological changes are four orders-of-magnitude slower than in liquid water, suggesting that interfacial resistance limits the penetration of water into the membrane. Also, upon water absorption from liquid water, a structural rearrangement from a di...
TL;DR: In this paper, the specific capacity and cycling stability of lithium sulfur batteries have been investigated with respect to the chemical composition and fabrication process of the sulfur electrode, and three different kinds of electrode compositions (containing Nafion, polyacrylonitrile/carboxymethylcellulose, and Teflon, respectively, as binder materials) have been tested.
TL;DR: In this article, the authors carried out systematic measurements of water uptake, proton conductivity and water self-diffusion coefficient in commercial Nafion N115 and NRE212 membranes.
TL;DR: In this article, two or four pendent methoxyphenyl groups were synthesized by bromination of bis(4-fluorophenyl)sulfone, followed by Suzuki coupling with 4-methoxybenzeneboronic acid.
TL;DR: A study of radiation grafted polymers on the conductivity and performance of alkaline anion exchange membrane fuel cells (AAEMFCs) is reported in this paper, where the authors used the radiation grafting technique to extract polymers from aminated poly(LDPE-g-VBC), poly(HDPEg-g -VBC) and poly(ETFE- g-VBP) membranes.
TL;DR: In this article, the performance of two-chambered microbial fuel cells (MFCs) using anion exchange membrane (AEM) was evaluated under batch mode with Shewanella putrefaciens in Luria broth.
TL;DR: In this article, a Nafion/TiO2 hybrid membrane was fabricated by a hydrothermal method to improve the performance of a vanadium redox battery (VRB) separator.
Abstract: To improve the performance of Nafion membrane as a separator in vanadium redox battery (VRB) system, a Nafion/TiO2 hybrid membrane was fabricated by a hydrothermal method. The primary properties of this hybrid membrane were measured and compared with the Nafion membrane. The Nafion/TiO2 hybrid membrane has a dramatic reduction in crossover of vanadium ions compared with the Nafion membrane. The results of scanning electron microscope, energy dispersive X-ray spectroscopy, and X-ray diffraction of the hybrid membrane revealed that the TiO2 phase was formed in the bulk of the prepared membrane. Cell tests identified that the VRB with the Nafion/TiO2 hybrid membrane presented a higher coulombic efficiency (CE) and energy efficiency (EE), and a lower self-discharge rate compared with that of the Nafion system. The CE and EE of the VRB with the hybrid membrane were 88.8% and 71.5% at 60 mA cm−2, respectively, while those of the VRB with Nafion membrane were 86.3% and 69.7% at the same current density. Furthermore, cycling tests indicated that the Nafion/TiO2 hybrid membrane can be applied in VRB system.
TL;DR: The novel amperometric biosensor fabricated through the layer-by-layer self-assembling of amine-terminated ionic liquid, and sulfonic acid, and graphene by covalent bonding was proved to be sensitive and reproducible, which enabled its promising application in physiology and pathology.
TL;DR: In this paper, a blend membrane consisting of sulfonated poly(ether sulfone) (SPES) and sulfonate poly (ether ether ketone), called SPES/SPEEK, for vanadium redox flow battery (VRB) was fabricated and characterized.
TL;DR: In this article, contact angle, voltammetry and mass transfer rate measurements were performed on eight cation exchange membranes with different surface morphology and the degree of hydrophobicity.