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Title: Atomistic Simulations of Perfluoro Phosphonic and Phosphinic Acid Membranes and Comparisons to Nafion

Abstract

We used classical molecular dynamics (MD) simulations to investigate the nanoscale morphology and proton transport properties of perfluoro phosphonic (FPA) and phosphinic acid (FPA-I) membranes as they are being considered for use in low temperature fuel cells. We systematically investigated these properties as a function of the hydration level. The changes in nanostructure, in transport dynamics of water and hydronium ions, and in water network percolation were extracted from MD simulations and compared with Nafion. Phosphonic and phosphinic acid moieties in FPA and FPA-I, have lower acidity than sulfonic acid in Nafion, yet the diffusion of water was observed to be faster in FPA and FPA-I than in Nafion, particularly at low hydration levels. However this did not give rise to notable differences in hydronium ion diffusion and water network percolation for these membranes over Nafion. Similar observations were also reported by our group recently in a study of perfluoro-sulfonyl imide membranes carrying stronger super-acids than sulfonic acid of Nafion. These findings together suggest no strong apparent correlation between the acidity strength of the functional acid groups and the dynamics of water and hydronium ions in hydrated polymer electrolyte membranes (PEMs) with similar fluorocarbon backbones and acidic group-carrying side chains.more » This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.« less

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1012281
Report Number(s):
PNNL-SA-76901
Journal ID: ISSN 1520--6106; 40083; KC0302020; TRN: US201109%%761
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry B, 115(12):2959-2969
Additional Journal Information:
Journal Volume: 115; Journal Issue: 12; Journal ID: ISSN 1520--6106
Country of Publication:
United States
Language:
English
Subject:
30 DIRECT ENERGY CONVERSION; DIFFUSION; ELECTROLYTES; FUEL CELLS; FUNCTIONALS; HYDRATION; IMIDES; MEMBRANES; MORPHOLOGY; OXONIUM IONS; PH VALUE; PHOSPHINIC ACIDS; POLYMERS; PROTON TRANSPORT; SULFONIC ACIDS; TRANSPORT; WATER; Polymer electrolyte membranes; acidity; molecular dynamics; percolation; Environmental Molecular Sciences Laboratory

Citation Formats

Idupulapati, Nagesh B, Devanathan, Ramaswami, and Dupuis, Michel. Atomistic Simulations of Perfluoro Phosphonic and Phosphinic Acid Membranes and Comparisons to Nafion. United States: N. p., 2011. Web. doi:10.1021/jp111972h.
Idupulapati, Nagesh B, Devanathan, Ramaswami, & Dupuis, Michel. Atomistic Simulations of Perfluoro Phosphonic and Phosphinic Acid Membranes and Comparisons to Nafion. United States. doi:10.1021/jp111972h.
Idupulapati, Nagesh B, Devanathan, Ramaswami, and Dupuis, Michel. Thu . "Atomistic Simulations of Perfluoro Phosphonic and Phosphinic Acid Membranes and Comparisons to Nafion". United States. doi:10.1021/jp111972h.
@article{osti_1012281,
title = {Atomistic Simulations of Perfluoro Phosphonic and Phosphinic Acid Membranes and Comparisons to Nafion},
author = {Idupulapati, Nagesh B and Devanathan, Ramaswami and Dupuis, Michel},
abstractNote = {We used classical molecular dynamics (MD) simulations to investigate the nanoscale morphology and proton transport properties of perfluoro phosphonic (FPA) and phosphinic acid (FPA-I) membranes as they are being considered for use in low temperature fuel cells. We systematically investigated these properties as a function of the hydration level. The changes in nanostructure, in transport dynamics of water and hydronium ions, and in water network percolation were extracted from MD simulations and compared with Nafion. Phosphonic and phosphinic acid moieties in FPA and FPA-I, have lower acidity than sulfonic acid in Nafion, yet the diffusion of water was observed to be faster in FPA and FPA-I than in Nafion, particularly at low hydration levels. However this did not give rise to notable differences in hydronium ion diffusion and water network percolation for these membranes over Nafion. Similar observations were also reported by our group recently in a study of perfluoro-sulfonyl imide membranes carrying stronger super-acids than sulfonic acid of Nafion. These findings together suggest no strong apparent correlation between the acidity strength of the functional acid groups and the dynamics of water and hydronium ions in hydrated polymer electrolyte membranes (PEMs) with similar fluorocarbon backbones and acidic group-carrying side chains. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.},
doi = {10.1021/jp111972h},
journal = {Journal of Physical Chemistry B, 115(12):2959-2969},
issn = {1520--6106},
number = 12,
volume = 115,
place = {United States},
year = {2011},
month = {3}
}