质子交换膜燃料电池催化层介尺度结构演化模拟及验证

The durability of proton exchange membrane fuel cell (PEMFC) is one of the important problems to be solved urgently for the commercialization, and the cell performance is closely related to the microstructure of the catalytic layers (CLs). Thus the corresponding micro-scale models of CLs are needed and applied to optimize the fabrication process and predict the durability life. At present, the related research has just been started in both domestic and aboard, and is considered as one of the R&D hotspots and trends of PEMFC...In this project, the coarse grained-molecular dynamics method (CG - MD) is adopted as a systematic method to study the evolution of the CL microstructure in the preparation steps and the corrosion process. First of all, depending on the microscale model, the fabrication process and conditions are investigated to understand the relations between microstructure and preparing conditions of CLs; and then, combined with the micro-structure analysis methods (“rolling probe method” and etc. ) and related experiment technologies, the characteristic parameters can be analyzed and validated. By using of this method, the characteristic parameters of CLs, such as porosity and specific surface area, are further compared to reveal the change rule in different stages of the corrosion process. Thus, the durability of the electrode can be predicted from the microscale “point”, laying the foundation for a more stable and excellent CL design.

质子交换膜燃料电池（PEMFC）性能衰减与催化层微观结构状态密切相关，如能开发相应的纳微米尺度模型，并应用于催化层制备工艺优化，可节省大量的人力物力资源。.本项目将催化层特征结构定义为系统(大尺度)；将构成的Pt、C原子簇及Nafiion分子链等单元体定义为单元(小尺度)。首先采用粗粒化处理的分子动力学方法（CG-MD）模拟催化层内多组分之间的协同机制，获得催化层制备过程各主要步骤中微观结构的自组织发展情况，探索催化层微观结构形成和演化的基本规律。针对重构的微观结构，将采用“滚动探头”等方法分析微观结构参数并结合实验进行验证。从微观结构角度揭示孔隙率、活性比表面积等特征参数的变化规律，阐明Pt纳米颗粒的生长机理，解决电极寿命预测问题。本项目的成功实施将为建立和完善催化层微观过程研究奠定基础，对设计稳定的、性能优异的催化层结构具有重要的理论意义和工程应用价值。

质子交换膜燃料电池（PEMFC）催化层内部含有复杂的纳微米尺度的孔结构，对电化学反应的发生及传质传热过程有着重要影响，是当前研究的重点和难点。.本项目针对质子交换膜燃料电池中，介于催化层内部分子/原子和宏观催化层之间的物相结构进行研究，提出了一种催化层微观模型的介尺度建模方法，用于明确催化层制备过程中控制机制及其相互关系。该方法采用的分子动力学（CD-MD）模型能够综合考虑催化层制备过程中操作步骤及环境因素(如溶剂极性)造成的影响，可反映催化层内部的初级孔、二级孔及各组分颗粒结构，获得包括固相和孔隙空间的三维表面信息，并讨论、优化催化层内部的机理问题，如铂单载量、碳腐蚀机理、孔隙率等；从而阐释催化层微观结构的形成机理及其对传递过程（电池整体性能）的影响。.另外，本项目集催化层微观结构研究、方法验证及模型应用于一体，从原子尺度结构计算跨越到几十个纳米尺度的分子动力学模拟，具有一定的集成特色。其中根据孔径分布测量实验和 “滚动探头”技术的原理相似性，研究溶剂极性对微观结构的变化，得到活性比面积、孔隙率等微观参数的发展规律，探索了一条从微观结构解决宏观问题的新途径。同时，为燃料电池跨尺度，多物理场耦合过程的模型建立打下良好的基础。