Ab initio molecular dynamics simulation of proton hopping in a model polymer membrane
We report the results of ab initio molecular dynamics simulations of a model NafionTM polymer membrane initially equilibrated using classical molecular dynamics simulations. We studied three hydration levels (λ) of 3, 9, and 15 H2O/SO3- corresponding to dry, hydrated and saturated fuel cell membrane, respectively. The barrier for proton transfer from the SO3-–H3O+ contact ion pair to a solvent-separated ion pair decreased from 2.3 kcal/mol for λ = 3 to 0.8 kcal/mol for λ = 15. The barrier for proton transfer between two water molecules was in the range from 0.7 to 0.8 kcal/mol for the λ values studied. The number of proton shuttling events between a pair of water molecules is an order of magnitude more than the number of proton hops across three distinct water molecules. The proton diffusion coefficient at λ = 15 is about 0.9x10-5 cm2/s, which is in good agreement with experiment and our previous quantum hopping molecular dynamics simulations.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1118109
- Report Number(s):
- PNNL-SA-98829
- Journal Information:
- Journal of Physical Chemistry B, 117(51):16522-16529, Journal Name: Journal of Physical Chemistry B, 117(51):16522-16529
- Country of Publication:
- United States
- Language:
- English
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