Enhancement of water management in PEM fuel cells

在过去的一个世纪里，由于温室效应（主要是由释放到大气中的二氧化碳水平增加引起的），气候发生了巨大变化。此外，尽管通过广泛的媒体报道提高了公众的认识，但工业和机动车辆的排放仍然是造成空气污染的主要原因，据加拿大卫生部称，每年在加拿大造成数千人死亡。气候变化和空气污染的主要原因是化石燃料的燃烧。鉴于这些问题，必须探索替代能源。质子交换膜（PEM）燃料电池作为一种高效、低排放的能源在近十年来受到了广泛的关注。然而，PEM燃料电池的性能和成本必须得到显著改善，才能形成一个可行的市场。目前PEM燃料电池的主要问题之一是水的管理。质子交换膜燃料电池的聚合物膜需要充分水化以保持质子的导电性。然而，由于长时间运行或输出电流大，过多的水蒸气冷凝会形成微液滴，阻碍反应物气体进入反应部位。水管理的改进需要研究燃料电池内部网络中液滴的形成和液态水的输送。该研究项目主要研究三种机制：1)膜电极组件不同层上微液滴的形成，2)气体扩散层（GDL）中液态水的输送，以及3)液滴在GDL/流道界面上的团聚。为了更好地了解这些机制，需要确定界面和毛细力对PEM燃料电池中液滴形成和液体运输的影响。本研究计划将发展实验方法，以确定1)微液滴在MEA中的局部界面特性，2)GDL的润湿性，以及3)微液滴在GDL/流道界面的界面特性。这项工作将加强PEM燃料电池的水管理，从而有助于加强加拿大燃料电池技术。

In the past century, there has been a dramatic climate change due to the greenhouse effect mainly caused by increased levels of carbon dioxide released into the atmosphere. Also, despite public awareness through extensive media coverage, emissions from industry and motor vehicles are still the main cause of air pollution that claims thousands of lives in Canada every year according to Health Canada. The primary cause of both climate change and air pollution is the burning of fossil fuels. In view of these problems, alternative sources of energy must be explored. Proton exchange membrane (PEM) fuel cells have drawn much attention in the last decade as a high-efficiency and low-emission source of energy. However, the performance and cost of the PEM fuel cells must be improved significantly before they can constitute a viable market. One of the major problems of the current PEM fuel cells is water management. The polymer membrane of the PEM fuel cell needs to be well hydrated to maintain proton conductivity. However, excessive water vapor condensation, due to a long operation or large output current, forms micro-droplets that block the access of the reactant gas to the reaction site. The improvement of water management requires the study of droplet formation and liquid water transport in the internal network of the fuel cell. The proposed research program involves the study of three mechanisms: 1) micro-droplet formation on different layers of the membrane electrode assembly (MEA), 2) liquid water transport in the gas diffusion layer (GDL), and 3) droplet agglomeration at the GDL/flow channel interface. To gain better insight into these mechanisms, it is required to determine the effect of interfacial and capillary forces on droplet formation and liquid transport in the PEM fuel cell. Experimental methodologies will be developed under this research program to determine 1) the local interfacial properties of the micro-droplets in the MEA, 2) the wettability of the GDL, and 3) the interfacial properties of the droplets at the GDL/flow channel interface. This work will result in the enhancement of water management in the PEM fuel cells and hence contribute to the strengthening of Canadian fuel cell technology.