Molecular Dynamics Analysis of Proton Diffusivity in Hydrated Nafion Membranes Contaminated with Ferrous Ions. Issue 1 (29th November 2019)

• Record Type: Journal Article
• Authors: Kawai, Kiyoto; Mabuchi, Takuya; Tokumasu, Takashi
• Is Part Of: Macromolecular theory and simulations. Volume 29:Issue 1(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-11-29
• Subjects: Gorotthuss mechanism -- Nafion membrane -- polymer morphology -- proton transport -- reactive molecular dynamics; Macromolecules -- Periodicals; Polymers -- Periodicals; Polymerization -- Periodicals; Macromolécules -- Périodiques; 547.705
• DOI: 10.1002/mats.201900047
• Languages: English
• ISSNs: 1022-1344

Abstract

Abstract: A molecular dynamics simulation is performed to understand the effects of ferrous ion contaminations on the proton transport property and nanostructures of solvent molecules in hydrated Nafion membranes while considering the Grotthuss mechanism. At low hydration conditions, the proton diffusivity has a local maximum at a certain concentration of ferrous ions. In the case of low ferrous ion concentration (≈25% of total cation charge), proton diffusivity is similar to that in the pure membrane. Also, in the case of middle ferrous ion concentration (50%), proton diffusivity is enhanced because the water clusters are more connected compared with those in the pure membrane. In the case of high ferrous ion concentration (larger than 70%), proton diffusivity is inhibited because the water clusters are disintegrated by the ferrous ions. Moreover, the correlation between proton diffusivity and nanostructure of the Nafion membrane is different among low, middle, and high water content. The results imply that the proton diffusivity is affected by ferrous ion contaminations by different mechanisms according to water content. Abstract : In Nafion membranes with low hydration conditions, at a ferrous ion concentration of 50%, the proton diffusivity is enhanced by the increase in the connectivity of water clusters because of the ferrous ions, whereas at a high concentration of ferrous ions, the proton diffusivity is inhibited by the strong electrostatic repulsion between ferrous ions.