Ab initio study of hydration and proton dissociation in ionomer membranes

Nagesh Idupulapati, Ram Devanathan, Michel Dupuis

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

We present a comparative study of proton dissociation in various functional acidic units that are promising candidates as building blocks for polymeric electrolyte membranes. Minimum energy structures for four acidic moieties with clusters of 1-6 water molecules were determined using density functional theory at the B3LYP/6-311G* level starting from chemically rational initial configurations. The perfluoro sulfonyl imide acid group (CF3CF 2SO2NHSO2CF3) was observed to be the strongest acid, due to the substantial electron withdrawing effect of both fluorocarbon groups. The hydrophilic functional group (CH3OC 6H3OCH3C6H4SO 3H) of sulfonated polyetherether ketone (SPEEK) membrane was found to be the strongest base, with the acidic proton dissociation requiring the addition of six water molecules and the hydrated proton being more tightly bound to the conjugate base. Even though both perfluoro sulfonyl imides and sulfonic acids (hydrophilic functional groups for sulfonyl imide and Nafion ionomers, respectively) required only three water molecules to exhibit spontaneous proton dissociation, the largest possible solvent-separated hydronium ion was attained only for the sulfonyl imide moiety. These results provide a rationale for the enhanced conductivity of perfluorinated sulfonyl imide-based membranes relative to that of the widely used Nafion membrane.

Original languageEnglish
Pages (from-to)6904-6912
Number of pages9
JournalJournal of Physical Chemistry A
Volume114
Issue number25
DOIs
Publication statusPublished - Jul 1 2010

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Imides
Ionomers
imides
Hydration
hydration
Protons
dissociation
membranes
Membranes
protons
Functional groups
Molecules
Water
water
hydronium ions
Fluorocarbons
molecules
acids
Acids
Sulfonic Acids

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Ab initio study of hydration and proton dissociation in ionomer membranes. / Idupulapati, Nagesh; Devanathan, Ram; Dupuis, Michel.

In: Journal of Physical Chemistry A, Vol. 114, No. 25, 01.07.2010, p. 6904-6912.

Research output: Contribution to journalArticle

Idupulapati, Nagesh ; Devanathan, Ram ; Dupuis, Michel. / Ab initio study of hydration and proton dissociation in ionomer membranes. In: Journal of Physical Chemistry A. 2010 ; Vol. 114, No. 25. pp. 6904-6912.
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