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Title: Interplay between water uptake, ion interactions, and conductivity in an e-beam grafted poly(ethylene-co-tetrafluoroethylene) anion exchange membrane

We demonstrate that the true hydroxide conductivity in an e-beam grafted poly(ethylene-co-tetrafluoroethylene) [ETFE] anion exchange membrane (AEM) is as high as 132 mS cm-1 at 80 °C and 95% RH, comparable to a proton exchange membrane, but with very much less water present in the film. To understand this behaviour we studied ion transport of hydroxide, carbonate, bicarbonate and chloride, as well as water uptake and distribution. Water uptake of the AEM in water vapor is an order of magnitude lower than when submerged in liquid water. In addition 19F pulse field gradient spin echo NMR indicates that there is little tortuosity in the ionic pathways through the film. A complete analysis of the IR spectrum of the AEM and the analyses of water absorption using FT-IR led to conclusion that the fluorinated backbone chains do not interact with water and that two types of water domains exist within the membrane. The reduction in conductivity was measured during exposure of the OH- form of the AEM to air at 95% RH and was seen to be much slower than the reaction of CO2 with OH- as the amount of water in the film determines its ionic conductivity and at relativemore » wet RHs its re-organization is slow.« less
Authors:
 [1] ;  [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [1] ;  [4] ;  [4] ;  [5] ;  [1] ;  [2] ;  [1]
  1. Colorado School of Mines, Golden, CO (United States)
  2. Univ. of Padova (Italy)
  3. Univ. of Padova (Italy);Veneto Nanotech (Italy)
  4. Univ. of Surrey, Guildford (United Kingdom)
  5. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
OSTI Identifier:
1214333
Grant/Contract Number:
AC02-06CH11357; EP/I004882/1; W911NF-11-1-0462; CHE-0923537
Type:
Accepted Manuscript
Journal Name:
Physical Chemistry Chemical Physics. PCCP (Print)
Additional Journal Information:
Journal Name: Physical Chemistry Chemical Physics. PCCP (Print); Journal Volume: 17; Journal Issue: 6; Journal ID: ISSN 1463-9076
Publisher:
Royal Society of Chemistry
Research Org:
Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY