Water Management in PEM Fuel Cells by Material Engineering

摘要：Trung V. Nguyen机构：堪萨斯大学提案编号：0651758标题：通过材料制造实现PEM燃料电池中的水管理质子交换膜（PEM）燃料电池依赖于适当的水管理来获得高功率密度和能源效率。 在操作期间，水通过电渗从阳极被拖到阴极，导致在阳极处脱水。同时，除了通过电渗从阳极输送水之外，还通过氧还原反应在阴极处产生水。 当通过这些过程在阴极中产生的水没有被适当地去除时，其积聚导致差的燃料电池性能，因为其阻塞用于氧输送的气孔并在反应区域上形成额外的输送屏障。 传统上，水管理是通过系统工程来解决的，即，通过向基本燃料电池系统添加辅助系统以向阳极提供加湿并从阴极除去水。 这种方法大大增加了系统的复杂性（例如可靠性和耐用性）和成本。 此外，这些辅助系统降低了燃料电池系统的净功率输出，导致转换效率降低。 最近的发展和对PEM燃料电池中使用的一些组件的功能的理解已经导致了关于如何在PEM燃料电池中实施水管理的范式转变。 据信，如果使用具有正确性质和正确电极配置的材料，则通过电渗透输送到阴极的水可以被迫通过膜返回到阳极，以在PEM燃料电池中实现零净水输送穿过膜的条件。 这种方法消除了对阳极气体加湿的需要，并使阴极处的水去除要求最小化，从而允许PEM燃料电池系统大大简化。 为了更有效地实现上述目标，计划采用理论（建模）和实验工作相结合的方法。 实验将进行测量的膜和电极组件（MEA）的质子交换膜燃料电池中使用的关键组件的两相传输特性。 结果将被用来开发这些组件的形态和润湿性能和两相传输性能之间的关系的相关性。 还将进行实验以开发用于PEM燃料电池中的催化剂层的四相（电子-离子-气体-液体）微结构，其对于两相（液体和气体）传输是最佳的。 同时，一个完整的MEA的PEM燃料电池，结合从上述实验中获得的两相传输特性的数学模型将被开发。 一旦模型的预测通过实验验证，该模型将用于优化研究，以确定在PEM燃料电池中实现零净水传输跨膜条件所需的电极配置和组件的形态和表面特性。 基于优化结果，将开发新的组件并在PEM燃料电池中进行测试，以验证实现了零净水传输的条件。更广泛的影响：首先，这种利用材料工程实现最佳水管理的方法将显著降低PEM燃料电池系统的复杂性和成本，并有助于加速该技术的商业化。 第二，这项工作的成果预计将在基础科学和应用科学层面的其他领域产生影响。对多孔介质中多相输运的理解适用于地质、核工程和石油工程等领域。 PI还计划继续招募不同背景，性别和种族的本科生和研究生加入他的研究团队。 他将燃料电池技术引入本科教育的努力得到了他创立的公司创建的教育工具（实验和文献）的认可。

ABSTRACTPI: Trung V. Nguyen Institution: University of KansasProposal Number: 0651758Title: WATER MANAGEMENT IN PEM FUEL CELLS BY MATERIAL ENGINEERINGProton Exchange Membrane (PEM) fuel cells depend on proper water management to obtain high power density and energy efficiency. During operation water is dragged from the anode to the cathode by electro-osmosis leading to dehydration at the anode. Concurrently, in addition to water being transported from the anode by electro-osmosis, water is also generated at the cathode by the oxygen reduction reaction. When the water created in the cathode by these processes is not properly removed, its accumulation leads to poor fuel cell performance because it blocks the gas pores used for oxygen transport and forms an additional transport barrier over the reactive area. Traditionally, water management has been addressed by system engineering, i.e., by adding auxiliary systems to the basic fuel cell system to provide humidification to the anode and removal of water from the cathode. This approach has added significant complexities (e.g. reliability and durability) and costs to the system. Furthermore, these auxiliary systems reduce the net power output of the fuel cell system leading to lower conversion efficiency.Intellectual Merit: Recent development and understanding of the functions of some of the components used in a PEM fuel cell have led to a paradigm shift as to how water management can be implemented in a PEM fuel cell. It is believed that if materials with the right properties and the correct electrode configuration are used, the water transported to the cathode by electro-osmosis can be forced back through the membrane to the anode to achieve the condition of zero-net-water-transport-across-the membrane in a PEM fuel cell. This approach eliminates the need for anode gas humidification and minimizes the water removal requirement at the cathode, allowing the PEM fuel cell system to be greatly simplified. These are the intellectual merits of this work.To achieve the objective stated above in a more efficient manner, a combined approach of theoretical (modeling) and experimental work is planned. Experiments will be conducted to measure the two-phase transport properties of the key components used in the membrane-and-electrode assembly (MEA) of a PEM fuel cell. The results will be used to develop correlations of the relationship between the morphological and wetting properties and the two-phase transport properties of these components. Experiments will also be conducted to develop a four-phase (electronic-ionic-gas-liquid) micro-structure for the catalyst layer used in PEM fuel cell that is optimal for two-phase (liquid and gas) transport. Concurrently, a mathematical model of a complete MEA of a PEM fuel cell that incorporates the two-phase transport properties obtained from the experiments above will be developed. Once the model's predictions are validated experimentally, the model will be used in an optimization study to determine the electrode configuration and the morphological and surface properties of the components needed to achieve the zero-net-water-transport-across-the-membrane condition in a PEM fuel cell. Based on the optimization results new components will be developed and tested in a PEM fuel cell to validate that the condition of zero-net-water-transport-across-the-membrane is achieved.Broader Impact: First, this approach of using materials engineering to achieve optimal water management should significantly lower the complexities and costs of the PEM fuel cell system and help accelerate the commercialization of this technology. Second, the results of this work are expected to have impacts in other areas at both the basic and applied science levels. The understanding of multi-phase transport in porous media is applicable in areas such as geology, nuclear engineering and petroleum engineering. The PI also plans to continue recruiting undergraduate and graduate students of various backgrounds, genders and ethnicity in his research team. His efforts to introduce fuel cell technology to the undergraduate education are well recognized by the educational tools (experimental and literature) created by a company that he founded.