J056031 分子動力学法を用いた水和ナフィオン内の水・プロトン輸送特性の解析

Abstract

We have performed an atomistic analysis of the vehicular transport of hydronium ions and water molecules in the nanostructure of hydrated Nafion membrane by systematically changing the hydration level using classical molecular dynamics simulations. The models of Nafion membrane based on DREIDING force field with modification of torsion potential are proposed and validated by comparing the density, water diffusivity, and Nafion morphology with experimental data. The simulated final density agrees with experiment within 1.3 % for various water contents and the trends that density decreases with increasing hydration level are reproduced. In addition to determination of diffusion coefficients of liquid molecules as a function of hydration level for dynamical analysis, we have also implemented the cluster analysis of liquid molecules for structural insight. The cluster analysis provides insights into the network formation of water channel at water content I = 6. The diffusion coefficient of water molecules is found to be in good agreement with experimental data. The diffusion coefficient of hydronium ions has showed that general trends in the experimental data are reproduced although the classical models have the limitation of hydronium dynamics.