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Ionic Liquid Confined in Nafion: Toward Molecular-Level Understanding

Authors

  • Delin Sun,

    1. School of Chemistry and Chemical Engineering, Guangdong Provincial Key Laboratory for Green Chemical Product Technology, South China University of Technology, Guangzhou, P.R. China
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  • Jian Zhou

    Corresponding author
    • School of Chemistry and Chemical Engineering, Guangdong Provincial Key Laboratory for Green Chemical Product Technology, South China University of Technology, Guangzhou, P.R. China
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Correspondence concerning this article should be addressed to J. Zhou at jianzhou@scut.edu.cn.

Abstract

In this article, multiscale simulation methods were used to study structural and transport properties of Nafion–ionic liquid composite membranes that are novel proton conducting materials for fuel cells. Coarse-grained model for 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) ionic liquid was first developed in the framework of BMW-MARTINI force field. Coarse-grained simulation results of bulk [bmim][BF4] ionic liquid show good agreement with all-atom simulation results and experimental data. Nafion–[bmim][BF4] composite membranes were then simulated using all-atom and coarse-grained models. Ionic liquid cluster formation inside Nafion was revealed by coarse-grained simulations. Diffusion coefficients of both [bmim]+ cations and math formula anions are reduced by one to two orders of magnitude depending on their concentrations in Nafion membrane. [Bmim]+ cations have faster self-diffusion coefficient than math formula anions, while this phenomenon is more pronounced when ionic liquids are confined in Nafion. This work provides molecular basis for understanding Nafion–ionic liquid composite membranes. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2630–2639, 2013

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