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Nafion

About: Nafion is a research topic. Over the lifetime, 9110 publications have been published within this topic receiving 320865 citations.


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Journal ArticleDOI
TL;DR: In this article, the Nafion membrane is modified by sputtering a thin layer of Pt/Pd-Ag/Pt on its surface in order to reduce methanol crossover.

123 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated the room-temperature proton conductivity, coordination geometry, and pore-diameter distribution of the title Cu(II) coordination polymer and revealed that the present Cu coordination polymer was revealed to possess porous space of about 6 A, which includes much water molecules more than 10H2O per unit cell.

122 citations

Journal ArticleDOI
TL;DR: Curing at 120 degrees C can be used to improve the in vivo durability of a miniaturized glucose sensor with an outer coating of the Dupont perfluorinated ionomer, Nafion, and several of the fully assembled, heat-cured, needle-type glucose sensors remained functional for at least 10 days after subcutaneous implantation in dogs.
Abstract: In this paper we report that curing at 120 degrees C can be used to improve the in vivo durability of a miniaturized glucose sensor with an outer coating of the Dupont perfluorinated ionomer, Nafion. Sensors based on glucose oxidase trapped in an albumin/glutaraldehyde matrix were able to withstand curing at 120 degrees C without noticeable change in electrode sensitivity (+/- 22% SD). Curing above 120 degrees C caused a gradual decline in sensitivity, with no sensitivity seen at 170 degrees C. Curing Nafion at 120 degrees C eliminated ascorbic acid and urea interferences and improved selectivity for glucose against uric acid and acetaminophen, compared to room temperature-cured Nafion coatings. The Nafion film reduced O2 demand by the sensor, so the signal was O2 independent across a partial pressure range of 8-140 mmHg. Several of the fully assembled, heat-cured, needle-type glucose sensors remained functional for at least 10 days after subcutaneous implantation in dogs, without degradation of their sensitivity (average 3 nA/mM in vivo at 37 degrees C and 6 nA/mM in vitro at 37 degrees C).

122 citations

Journal ArticleDOI
TL;DR: The results demonstrate that it is generally impossible to describe the low pH conditions in the hydrophilic domains of Nafion without the explicit treatment of Grotthuss delocalization in the underlying molecular dynamics model for the excess protons.
Abstract: Solvation properties of the hydrated excess proton are studied in a hydrophilic pocket of Nafion 117 through a series of molecular dynamics simulations. The multistate empirical valence bond (MS-EVB) methodology, which enables the delocalization of the excess proton through the Grotthuss hopping mechanism, was employed for one of the excess protons in the simulation cell. Simulations were performed such that "classical" nondissociable hydronium cations and a single excess proton treated with the MS-EVB methodology were at a concentration ratio of 39:1. Two degrees of hydration of the Nafion polymer electrolyte membrane were simulated, each displaying the same marked difference between the solvation structures of the classical versus MS-EVB treated (Grotthuss shuttling) excess proton species. These differences are attributed to the solvent dynamics needed to transfer the cation between the solvent separated and contact pair positions about the sulfonic acid counterion. The results demonstrate that it is generally impossible to describe the low pH conditions in the hydrophilic domains of Nafion without the explicit treatment of Grotthuss delocalization in the underlying molecular dynamics model for the excess protons.

122 citations

Journal ArticleDOI
TL;DR: Evidence of physical changes of aged Nafion films was obtained, and the results showed a permanent increase in the thickness of the Nafions film and a decrease in the scattering length density (SLD), which are attributed to irreversible swelling of theNafion film.
Abstract: Neutron reflectometry was used to examine the interactions of polymer electrolyte fuel cell (PEFC) materials that comprise the triple-phase interface. Smooth, idealized layers of Nafion on glassy carbon (GC) and Pt surfaces were used to experimentally model the PEFC electrode interfaces. Different multilayer structures of Nafion were found in contact with the Pt or GC surfaces. These structures showed separate hydrophobic and hydrophilic domains formed within the Nafion layer when equilibrated with saturated D(2)O vapor. A hydrophobic Nafion region was formed adjacent to a Pt film. However, when Nafion was in contact with a PtO surface, the Nafion at the Pt interface became hydrophilic. The adsorbed oxide layer caused a long-range restructuring of the perfluorosulfonic acid polymer chains that comprise Nafion. The thicknesses of the hydrophobic and hydrophilic domains changed to the same magnitude when the oxide layer was present compared to a thin hydrophobic domain in contact with Pt. A three-layer Nafion structure was formed when Nafion was in direct contact with GC. The findings in this research are direct experimental evidence that both the interfacial and long-range structural properties of Nafion are affected by the material with which it is in contact. Evidence of physical changes of aged Nafion films was obtained, and the results showed a permanent increase in the thickness of the Nafion film and a decrease in the scattering length density (SLD), which are attributed to irreversible swelling of the Nafion film. The aging also resulted in a decrease in the SLD of the GC substrate, which is likely due to either an increase in surface oxidation of the carbon or loss of carbon mass at the GC surface.

122 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023253
2022503
2021338
2020367
2019386
2018393