Proton 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.
