温度对质子交换膜扩散性能影响的分子动力学模拟

Molecular Dynamics Simulation of Temperture Effect on Diffusion Process of Water and Proton in Proton Exchange Membrane

为了研究Nafion膜的微细观结构及其输运特性,针对目前广为采用的Nafion 117膜并基于Materials Studio软件平台构建了一种分子动力学计算模型,在温度分别为300、353 K时,对其实施了计算,得到了不同水含量下Nafion 117膜的元胞结构,并依据该模型计算了水分子和水合氢离子的扩散系数.模拟结果表明:质子交换膜元胞的密度随水含量的增加而下降,和实验值基本一致,最大偏差在8%以内(300 K);当温度升高时,膜元胞密度降低,这与温度升高、膜体积膨胀导致密度降低的宏观分析完全一致.同时,研究了膜水含量、温度对水分子和水合氢离子在膜内的扩散系数的影响,增加水含量可以提高膜的质子传导率,同一温度下水含量越大,水分子和水合氢离子的扩散系数越大,且同一水含量下温度越高,水分子和水合氢离子的扩散系数越大.

A molecular dynamics calculation model for the Nafion 117 membrane was constructed with the Materials Studio（MS） software platform to study its micro-structure and transport properties.From the calculation model,cell structure of the Nafion 117 membrane with different water content at 300 K and 353 K was obtained,respectively,and the predicted density values of simulated cell are in good agreement with the experimental data.Moreover,temperature has a significant effect on the diffusion coefficients of both water molecules and hydrogen ions.At the same temperature,the predicted diffusion coefficients of both water molecules and hydrogen ions increase with the water content,and at the same water content,the predicted diffusion coefficients of both water molecules and hydrogen ions increase with the temperature.