水分子在质子交换膜中的电渗迁移的分子动力学模拟研究

项目名称： 水分子在质子交换膜中的电渗迁移的分子动力学模拟研究

项目编号： No.20873081

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 金属学与金属工艺

项目作者： 严六明

作者单位： 上海大学

项目金额： 22万元

中文摘要： 质子电导、水的电渗迁移、甲醇的穿透，是质子交换膜燃料电池的重要物理化学过程，是电池综合性能的决定因素。设计和制备质子交换膜的首要目标是提高质子电导率，降低水和甲醇的迁移率。在水的液态温区工作的燃料电池中，水的电渗迁移是设计水管理系统时需要考虑的主要因素，也是影响电池连续长时间工作关键。在直接甲醇燃料电池中，甲醇的穿透既降低了甲醇的使用效率，也影响了电池的综合性能。 利用分子模拟方法研究了质子电导、水的电渗、甲醇穿透，发展了计算带电离子和中性分子在电场作用下迁移速度的新方法。具体包括：建立离子和分子的速度分布函数，计算它们在电场中的迁移速度，以及水的电渗系数或甲醇穿透系数。在此基础上，建立了水和甲醇迁移的分子模型，探讨了膜的结构与水和甲醇迁移的关系。 利用量子化学方法研究酸-碱复合体系中的质子迁移，建立了膜的设计准则。建立、并用1H NMR验证了质子迁移与酸-碱平衡的关系，确立了质子迁移的协同效应。研究了膦酸-有机碱复合体系的结构及其氢键网络，氢键网络的重排及重排势垒。 设计并制备了掺杂磷酸的BPO4-ABPBI纳米复合膜、聚环己烯膦酸-PI复合膜，具良好综合性能。

中文关键词： 燃料电池；质子交换膜；电渗；分子动力学模拟；水管理

英文摘要： The protons transport and electroosmosis of neutral molecules (water and methanol molecules) under an electric field are fundamental physico-chemical processes for the proton exchange membrane fuel cells (PEMFCs) determining their comprehensive performances. The top target in the design and preparation of proton exchange membranes (PEMs) is to improve their proton conductivity. In PEMFCs operated under temperature range of liquid water, the electroosmosis of water is one of the essential factors in the design of the water management system, and is an urgent technical obstacle for the long time continuous operation of PEMFCs. In direct methanol fuel cells, methanol crossover not only limits the overall efficiency of methanol usage but also degrades the comprehensive performances of the fuel cells. In this project, the molecular dynamics simulations are applied to the study of proton transport, electroosmosis of water, and methanol crossover in the PEMs by developing a method to evaluate the migration velocity of various ions and neutral molecules under an electric field. We firstly built the velocity distribution functions of the ions and neutral molecules, then evaluated their migration velocities under an electric field, and finally calculated the electroosmosis coefficients of water or/and methanol. Based on these studies, water and methanol transport model was developed, the relationship between molecular structure of membrane and water and methanol transport under electric field was established. The quantum chemistry calculations were applied to the study of the proton transport in acid-base complexes, and the design criteria of PEMs for PEMFCs operated at high-temperature well above the boiling point of water were established. We established a relationship between proton transport and the acid-base equilibrium by quantum chemistry calculations, verified the relationship by 1H NMR spectra, and recognized the synergetic effect of proton transport in acid-base complexes. We also studied the microstructure of hydrogen-bond network, as well as the reorganization of hydrogen-bond network and the corresponding reorganization barrier in acid-base complexes consisting of various phosphonic acid and heterocyclic bases. Furthermore, we also designed and developed two types of high-temperature PEMs: phosphoric acid doped BPO3-ABPBI nanocomposite, and poly(1-cyclohexenyl phosphonic acid)-PI complex. These two types of high-temperature PEMs show promising comprehensive characteristics at temperatures as high as 180oC.

英文关键词： Fuel cell; proton exchange membrane; electroosmosis; molecular dynamics simulation; water management