Chloride enhances fluoride mobility in anion exchange membrane/polycationic systems

Ying Lung Steve Tse, Himanshu N. Sarode, Gerrick E. Lindberg, Thomas A. Witten, Yuan Yang, Andrew M. Herring, Gregory A. Voth

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

We have studied anion exchange membrane/polycationic systems with different percentages of fluoride and chloride as counterions by molecular dynamics simulations. We also experimentally measured the self-diffusion constant of fluoride in a diblock copolymer that has the same hydrophilic block and found satisfactory agreement with simulations within a factor of 2. At 300 K, our simulations showed that the self-diffusion constant of fluoride increases by about 70% when fluoride content decreases from 100% to 40% (and 60% Cl), and it increases by about 140% when fluoride content decreases from 100% to 10%. Increasing % Cl also slightly decreases the attraction between fluoride and the cations. We hypothesize that the root cause of the enhancement in fluoride mobility is due to the larger size of the chloride ion, which more readily loses its water solvation shells because of a lower charge/radius squared (surface electric field). This in turn frees up more water for ion transport. We believe this effect is likely more general than just the fluoride/chloride case reported here.

Original languageEnglish (US)
Pages (from-to)845-853
Number of pages9
JournalJournal of Physical Chemistry C
Volume118
Issue number2
DOIs
StatePublished - Jan 16 2014
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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