Transport phenomena in fuel cells

聚合物电解质膜燃料电池(PEMFC)是一种可为道路车辆、家庭和便携式电子设备提供清洁能源的电化学能量转换装置。燃料电池的运行和耐久性取决于几个传输过程的调节：反应物气体、产物水、热、电子和质子的流动以及反应动力学。这些过程发生在各种材料和部件中，这些材料和部件具有从纳米到厘米的特征。这项相对年轻和不断发展的技术的进一步进展受到现有知识边界上的运输现象问题的限制。关于多孔电极层的形态结构和传输参数的信息很少。液态水通常存在于质子交换膜燃料电池中，虽然这有助于保持聚合物膜的水合作用，但也会导致驱替；液态水的形成和传输机制尚不清楚。由于燃料电池的多层结构，可能会在界面处发生重大损失；界面现象需要表征和量化。质子交换膜燃料电池的现场环境使实验观测极具挑战性。我们提出了新的实验和计算方法来解决复合催化剂层中的纳米结构和传输现象，通过结合先进的显微技术、重建技术和孔尺度模拟来解决；b)测量和预测多孔电极的有效电导率；c)通过可视化和动态模拟提高对水传输这一具有挑战性的问题的理解；d)在多尺度计算框架中集成最先进的组件模型；以及e)验证和应用该模型以探索新的概念和策略来改善传输过程。

Polymer Electrolyte Membrane Fuel Cells (PEMFCs) are electrochemical energy conversion devices that can provide clean power to road vehicles, homes and portable electronics. The operation and durability of a fuel cell depend on the regulation of several transport processes: the flow of reactant gases, product water, heat, electrons and protons in conjunction with reaction kinetics. These processes take place in a variety of materials and components having characteristic features ranging from nanometers to centimeters. Further progress in this relatively young and evolving technology is limited by transport phenomena issues at the boundaries of current knowledge. Information on the morphological structure and transport parameters of the porous electrode layers is scarce. Liquid water is often present in PEMFCs, and while this helps maintain hydration of the polymer membrane, it also leads to flooding; the mechanisms of liquid water formation and transport are not well understood. Due to the multi-layered architecture of fuel cells, significant losses can occur at interfaces; the interfacial phenomena need to be characterized and quantified. The in-situ environment in a PEMFC makes experimental observations extremely challenging. We proposes new experimental and computational methods to: a) resolve the nano-structure and transport phenomena in composite catalyst layers by using a combination of advanced microscopy, reconstruction techniques and pore scale modelling; b) measure and predict the effective conductivities of porous electrodes; c) improve understanding of the challenging issue of water transport through visualization and dynamic simulations; d) integrate state-of-the art component models in a multi-scale computational framework; and e) validate and apply the model to explore novel concepts and strategies to improve transport processes.