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Title: Molecular Structure and Transport Dynamics in Perfluoro Sulfonyl Imide Membranes

We report a detailed and comprehensive analysis of the nanostructure, transport dynamics of water and hydronium and water percolation in hydrated perfluoro sulfonyl imides (PFSI), a polymer considered for proton transport in PEM fuel cells, using classical molecular dynamics simulations. The dynamical changes are related to the changes in the membrane nanostructure. Water network percolation threshold, the level at which a consistent spanning water network starts to develop in the membrane, lies between hydration level (λ) 6 and 7. The higher acidity of the sulfonyl imide acid group of PFSI compared to Nafion reported in our earlier ab initio study, translates into more free hydronium ions at low hydration levels. Nevertheless, the calculated diffusion coefficients of the H3O+ ions and H2O molecules as a function the hydration level were observed to be almost the same as that of Nafion, indicating similar conductivity and consistent with the experimental observations. This research was performed in part using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory, a U.S. Department of Energy (DOE) national scientific user facility located at the Pacific Northwest National Laboratory (PNNL). This work was supported by the US Department of Energy Basic Energy Sciences'more » Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.« less
Authors:
; ;
Publication Date:
OSTI Identifier:
1015894
Report Number(s):
PNNL-SA-73759
40083; KC0302020; TRN: US201112%%37
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physics. Condensed Matter, 23(23):Article No. 234106; Journal Volume: 23; Journal Issue: 23
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
30 DIRECT ENERGY CONVERSION; DIFFUSION; FUEL CELLS; HYDRATION; IMIDES; MEMBRANES; MOLECULAR STRUCTURE; OXONIUM IONS; PH VALUE; POLYMERS; PROTON TRANSPORT; TRANSPORT; WATER; proton transport; polymer electrolyte membranes; molecular dynamics; Environmental Molecular Sciences Laboratory