Molecular Dynamics Modeling of Proton Transport in Nation and Hylton Nanostructures
2010 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, no 18, 6056-6064 p.Article in journal (Refereed) Published
Classical molecular dynamics modeling studies at 363 K are reported of the local atomic-level and macroscopic nanostructures of two well-known perfluorosulfonic acid proton exchange polymer membrane materials: Nation and Hyflon. The influence of the different side-chain lengths in the two polymers on local structure is relatively small: Hyflon exhibits slightly greater sulfonate-group clustering, while Nation has more isolated side chains with a higher degree of hydration around the SO3- side-chain ends. This results in shorter mean residence times for water molecules around the end groups in Nation. Hyflon also displays a lower degree of phase separation than Nafion. The velocities of the water molecules and hydronium ions are seen to increase steadily from the polymer backbone/water interface toward the center of the water channels. Because of its shorter side chains, the number of hydronium ions is similar to 50% higher at the center of the water channels in Hyflon, and their velocities are similar to 10% higher. The water and H3O+ diffusion coefficients are therefore higher in the shorter side-chain Hyflon system: 6.5 x 10(-6) cm(2)/s and 25.2 x 10(-6) cm(2)/s, respectively; the corresponding values for Nation are 6.1 x 10(-6) cm(2)/s and 21.3 x 10(-6) cm(2)/s, respectively. These calculated values compare well with experiment: 4 x 10(-6) cm(2)/s for vehicular H3O+ diffusion.
Place, publisher, year, edition, pages
2010. Vol. 114, no 18, 6056-6064 p.
Research subject Chemistry with specialization in Inorganic Chemistry
IdentifiersURN: urn:nbn:se:uu:diva-137203DOI: 10.1021/jp903288yISI: 000277280500011OAI: oai:DiVA.org:uu-137203DiVA: diva2:377887