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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
26 Jul 2013-Science
TL;DR: Further development of microporous crystalline materials as proton conductors may lead to better electrolyte membranes for fuel cells, which could unlock the cost efficiencies enabled by humidity-independent operation above 100°C.
Abstract: Proton-exchange membrane fuel cells (PEMFCs) generate electricity because the electrons generated by the reaction of hydrogen and oxygen must travel through an external circuit; the membrane electrolyte only transfers protons. The membrane materials of choice have been ionomeric polymers, such as sulfonated fluoropolymers (Nafion), that achieve proton conductivities of up to 1 S cm−1, but the requirement to keep these materials hydrated limits their operating temperature and efficiency. Metal-organic frameworks (MOFs), in which inorganic assemblies are joined by organic linkers, have inherent porosity that could be exploited for the development of proton-conducting membranes. Among recent studies of experimental proton-conducting MOFs [e.g., ( 1 )], two general targets for PEMFC operation have emerged: developing better materials for operations under humid conditions (below 100°C), and developing efficient anhydrous proton conductors that could unlock the cost efficiencies enabled by humidity-independent operation above 100°C.

319 citations

28 Sep 2007
TL;DR: An electrolysis-cell design for simultaneous electrochemical reduction of CO 2 and H 2 O to make syngas (CO + H 2 ) at room temperature (25°C) was developed, based on a technology very close to that of proton exchange-membrane fuel cells (PEMFC) as mentioned in this paper.
Abstract: An electrolysis-cell design for simultaneous electrochemical reduction of CO 2 and H 2 O to make syngas (CO + H 2 ) at room temperature (25°C) was developed, based on a technology very close to that of proton-exchange-membrane fuel cells (PEMFC), i.e., based on the use of gas-diffusion electrodes so as to achieve high current densities. While a configuration involving a proton-exchange membrane (Nafion) as electrolyte was shown to be unfavorable for CO 2 reduction, a modified configuration based on the insertion of a pH-buffer layer (aqueous KHCO 3 ) between the silver-based cathode catalyst layer and the Nafion membrane allows for a great enhancement of the cathode selectivity for CO 2 reduction to CO [ca. 30 mA/cm 2 at a potential of -1.7 to -1.75 V vs SCE (saturated-calomel reference electrode)]. A CO/H 2 ratio of 1/2, suitable for methanol synthesis, is obtained at a potential of ca. -2 V vs SCE and a total current density of ca. 80 mA/cm 2 . An issue that has been identified is the change in product selectivity upon long-term electrolysis. Results obtained with two other cell designs are also presented and compared.

317 citations

Journal ArticleDOI
TL;DR: In this paper, perfluorinated ionomer membranes such as the Nafion membrane can be swollen with ionic liquids giving composite free standing membranes with excellent stability and proton conductivity in this temperature range while retaining the low volatility of the ionic liquid.
Abstract: Composite membranes that exhibit fast proton transport at elevated temperatures are needed for proton‐exchange‐membrane fuel cells and other electrochemical devices operating in the 100 to 200°C range. Traditional water‐swollen proton conducting membranes such as the Nafion membrane suffer from the volatility of water in this temperature range leading to a subsequent drop in conductivity. Here we demonstrate that perfluorinated ionomer membranes such as the Nafion membrane can be swollen with ionic liquids giving composite free‐standing membranes with excellent stability and proton conductivity in this temperature range while retaining the low volatility of the ionic liquid. Ionic conductivities in excess of 0.1 S/cm at 180°C have been demonstrated using the ionic liquid 1-butyl, 3-methyl imidazolium trifluoromethane sulfonate. Comparisons between the ionic‐liquid‐swollen membrane and the neat liquid itself indicate substantial proton mobility in these composites. © 2000 The Electrochemical Society. All rights reserved.

316 citations

Journal ArticleDOI
01 Jan 2016-Small
TL;DR: This work provides the rational design strategy for multifunctional separators at cell scale to effective utilizing of active sulfur and retarding of polysulfides, which offers the possibility of high energy density Li-S cells with long cycling life.
Abstract: The reversible electrochemical transformation from lithium (Li) and sulfur (S) into Li2 S through multielectron reactions can be utilized in secondary Li-S batteries with very high energy density. However, both the low Coulombic efficiency and severe capacity degradation limits the full utilization of active sulfur, which hinders the practical applications of Li-S battery system. The present study reports a ternary-layered separator with a macroporous polypropylene (PP) matrix layer, graphene oxide (GO) barrier layer, and Nafion retarding layer as the separator for Li-S batteries with high Coulombic efficiency and superior cyclic stability. In the ternary-layered separator, ultrathin layer of GO (0.0032 mg cm(-2) , estimated to be around 40 layers) blocks the macropores of PP matrix, and a dense ion selective Nafion layer with a very low loading amount of 0.05 mg cm(-2) is attached as a retarding layer to suppress the crossover of sulfur-containing species. The ternary-layered separators are effective in improving the initial capacity and the Coulombic efficiency of Li-S cells from 969 to 1057 mAh g(-1) , and from 80% to over 95% with an LiNO3 -free electrolyte, respectively. The capacity degradation is reduced from 0.34% to 0.18% per cycle within 200 cycles when the PP separator is replaced by the ternary-layered separators. This work provides the rational design strategy for multifunctional separators at cell scale to effective utilizing of active sulfur and retarding of polysulfides, which offers the possibility of high energy density Li-S cells with long cycling life.

311 citations


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