Study On Self-humidification FC With Current Collecting Plate

Perfluorinated sulfonic acid membrane is commonly used as solid electrolyte membrane for proton exchange membrane fuel cell at present. The water content in the membrane directly affects the proton conduction and membrane mechanical strength, and further affects the fuel cell s performance. So it is very important to maintain an appropriate membrane wetting. Usually, a variety of humidification meathods are used for humidifying the reaction gas, but this will increase the complexity of the system and the volume and weight. In order to simplify the system and improve the volume and mass ratio power, there have been many self-humidification methods by designing and optimizing the materials and structures of fuel cell in recent years. But results are not very good and not yet completely practical. In this paper, from the perspective of making self-humidification fuel cell practical and simplifying the water management system of the fuel cell, the author starts from the fuel cell s key material-current collecting plate material, using porous carbon plate to replace the traditional non-porous graphite plate as the material of current collecting plate. With experimental study on the water permeability and then designing structure layout and flow field of porous carbon plate, reaction gas is designed to be humified in the area of fuel cell' inlet where water is permeated from cooling water to cathode flow field while water is recovered in the area of fuel cell outlet where water is permeated from cathode flow field to cooling water. As a result, humidification system of fuel cell is eliminated and the water and heat management is combined.The main conclusions are as follows:(1) The water permeability of porous carbon plate is mainly affected by temperature and pressure gradient and increases linearly with temperature and pressure gradient increases.(2) By appropriate design of the structure and flow field of the current collecting plate and optimization of operating conditions, fuel cell is successfully operated under the condition of self-humidification and can stably work in a long time with cell voltage 0.6-0.65V at current density 600mA/cm2 under the condition ofλH2=1.5,λair=3.0 and water inlet pressure P=0.10MPa.(3) By appropriate design of the structure and flow field of the current collecting plate and optimization of operating conditions, water balance is achieved. That is the water permeates from cathode flow field outlet area to cooling water can supplement the water permeates from cooling water to cathode flow field inlet area caused by air humidification. When the water inlet pressure is 0.10MPa and the air outlet back pressure is 25KPa, the fuel cell performance under the self-humidification condition and the water recovery can achieve the best optimization.