质子交换膜燃料电池阴极催化剂层关键物系传递的多尺度模拟

The cathode catalyst layer in the polymer electrolyte membrane fuel cell (PEMFC) is the main limitation part for the energy conversion efficiency. The current research mainly focuses on the catalyst materials or the research of catalytic reaction mechanism inside the layer, the efficient reaction, diffusion and transfer of the key materials (proton, oxygen etc.) is important to optimize the multi-stage pore structure and improve the overall performance of the battery. In view of this situation and based on our research experience on multiscale simulation, this proposal aims to study the porous catalyst layer composed of perfluorosulfonic acid ionomer / Pt catalyst / carbon. The reaction and diffusion of key materials on active sites will be studied by ReaxFF (reactive force field) molecular dynamics at the microscale; and then, the diffusion and transfer in primary pores and meso-structure of aggregates will be explored by molecular dynamics with classic force field at the mesoscale; while the reconstruction of secondary pores structure and the following diffusion efficiency analysis will be included at the macroscale. Especially, the correlation and coupling between the simulation methods will be explored. Based on the rule of diffusion and transfer at difference scales, the simulation results should elucidate the relationship between transfer efficiency and multi - stage structure, which yield guidelines to the structural optimization and design of cathode catalyst layer.

阴极催化剂层是制约质子交换膜燃料电池整体能量转换效率的关键，目前针对该层的研究主要集中在催化剂材料及微观反应机理方面, 而关键物系（质子、氧分子等）反应、扩散传递规律的建立对优化设计该层多级孔道结构进而提升效能至关重要。针对这一现状并基于申请人多尺度模拟的研究基础，本项目拟以全氟磺酸离聚物/Pt催化剂/碳组成的阴极催化剂层为研究对象，在微尺度上采用反应力场分子动力学方法研究关键物系在活性位点上的反应扩散；在介尺度上采用经典力场分子动力学方法研究聚集体内初级孔道中的扩散传递和介观结构；在宏尺度上采用随机方法构建聚集体之间次级孔道结构并采用弹簧格子模型预测其扩散传递性能。尤其是探索各个尺度模拟方法间的关联与耦合，通过各尺度上的扩散传递规律来建立阴极催化剂层内部多级结构与关键物系传递性能之间的关系，从理论角度对阴极催化剂层的结构设计优化提供指导。

阴极催化剂层制约质子交换膜燃料电池的整体能量转换效率，而关键物系（反应物、产物等）反应、扩散传递规律的建立对优化设计该层多级孔道结构进而提升效能至关重要。本项目通过结合量化计算、分子动力学模拟、介观动力学及连续力学方法等多种不同尺度上的模拟方法，实现了阴极催化剂层内不同尺度结构上反应扩散传递行为的模拟。具体工作可分为以下三个部分，一、微尺度上活性位点的结构调控及关键物系的反应扩散；二、介尺度上初级孔道结构构建及关键物系的扩散传递；三、宏尺度的构效关系及多尺度模拟。通过完成上述研究内容，建立了关键物系、孔道结构、环境及扩散传递性能之间的构效关系，并针对活性位点上反应、扩散传递提供了微观机理解释，特别是在各尺度模拟方法的关联耦合及与实验关联方面，实现了分子间作用力与实验观测（接触角）之间的关联，提出了从组成到微观结构再到性能的连续多尺度模拟，建立了关键物系孔道内扩散调控的统一方程，上述工作可从理论角度对阴极催化剂层的结构设计优化提供指导。