质子交换膜燃料电池催化层微观结构重构与腐蚀过程机理研究

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）耐久性是其实现商业化亟待解决的重要问题之一，而电池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和寿命预测，可节省大量的人力物力资源。.本项目先对燃料电池催化层微观结构的形成过程进行模拟，即：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。在此基础上，将CG-MD微观模型应用于催化层腐蚀过程机理研究。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。本项目成功实施为建立和完善催化层微观过程研究奠定基础，对设计稳定、性能优异的催化层结构具有重要意义。

燃料电池催化层内部各组分和诸多物理化学过程之间的协同作用是系统产生新结构的直接根源，本项目以PEMFC催化层微观结构演化为对象，建立基于分子动力学粗粒化处理方法（CG-MD）的微观模型，通过分子动力学方法模拟各组分间协同作用，实现动力学推演，最终得到稳定的纳微米特征结构体。.项目中，数值模拟和实验室实验先后进行；先通过开发的微观结构分析方法，获得易于实验比对的参数，如Pt粒径分布、孔径分布、活性比表面积等，通过改变溶剂极性、组分配比等条件，实现平衡态微观结构比较，对制备工艺、组分含量参数进行优化；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，进一步得到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。