Atomistic simulation of water percolation and proton hopping in Nafion fuel cell membrane

Ram Devanathan, Arun Venkatnathan, Roger Rousseau, Michel Dupuis, Tomaso Frigato, Wei Gu, Volkhard Helms

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92 Citations (Scopus)

Abstract

We have performed a detailed analysis of water clustering and percolation in hydrated Nafion configurations generated by classical molecular dynamics simulations. Our results show that at low hydration levels H2O molecules are isolated and a continuous hydrogen-bonded network forms as the hydration level is increased. Our quantitative analysis has established a hydration level (λ) between 5 and 6 H2O/SO3 - as the percolation threshold of Nafion. We have also examined the effect of such a network on proton transport by studying the structural diffusion of protons using the quantum hopping molecular dynamics method. The mean residence time of the proton on a water molecule decreases by 2 orders of magnitude when the λ value is increased from 5 to 15. The proton diffusion coefficient in Nafion at a λ value of 15 is about 1.1 × 10-5 cm2/s in agreement with experiment. The results provide quantitative atomic-level evidence of water network percolation in Nafion and its effect on proton conductivity.

Original languageEnglish
Pages (from-to)13681-13690
Number of pages10
JournalJournal of Physical Chemistry B
Volume114
Issue number43
DOIs
Publication statusPublished - Nov 4 2010

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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