The effects of the hydrophobic environment on proton mobility in perfluorosulfonic acid systems

An ab initio molecular dynamics study

Bradley F. Habenicht, Stephen J. Paddison, Mark Tuckerman

Research output: Contribution to journalArticle

Abstract

Model systems of perfluorosulfonic acid (PFSA) polymers exhibiting regular shaped and idealized channel morphologies were constructed by functionalizing single walled carbon nanotubes (CNTs) with -CF2SO3H groups and adding from 1 to 3H2O/SO3H to investigate structural and chemical factors affecting proton dissociation and transport. No a priori assumptions about either the dissociation or hydration of the protons were assumed and extensive ab initio molecular dynamics (AIMD) simulations were performed and subject to analysis. The importance of the hydrophobic environment was assessed by comparing the hydration of the protons both with and without fluorine atoms attached to the CNT walls. The AIMD trajectories showed that dissociation of the acidic proton increased with increasing density of sulfonic acid groups; however, greater densities also brought about trapping of the dissociated proton. The fluorine atoms accepted hydrogen bonds from the water molecules, stabilized hydrogen bonding, and enhanced proton dissociation. The CNT systems without fluorination of the walls exhibited a propensity for the formation of Zundel cations (H5O2+), while the fluorinated systems favoured hydrated structures involving hydronium ions or hydrated H3O+ species depending on the amount of water in the system.

Original languageEnglish (US)
Pages (from-to)6342-6351
Number of pages10
JournalJournal of Materials Chemistry
Volume20
Issue number30
DOIs
StatePublished - Aug 14 2010

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Molecular dynamics
Protons
Acids
Carbon Nanotubes
Fluorine
Hydration
Carbon nanotubes
Hydrogen bonds
Atoms
Fluorination
Sulfonic Acids
Water
Single-walled carbon nanotubes (SWCN)
perfluorosulfonic acid
Cations
Polymers
Positive ions
Trajectories
Molecules
Computer simulation

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Chemistry

Cite this

The effects of the hydrophobic environment on proton mobility in perfluorosulfonic acid systems : An ab initio molecular dynamics study. / Habenicht, Bradley F.; Paddison, Stephen J.; Tuckerman, Mark.

In: Journal of Materials Chemistry, Vol. 20, No. 30, 14.08.2010, p. 6342-6351.

Research output: Contribution to journalArticle

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