MEA with a Hydrophilic GDL and Direct Evaluation of Water Flooding for GDLs

摘要

Intensive research and development activities have been carried out over the last few decades to improve the performance of polymer electrolyte fuel cells (PEFCs) [1-3], a promising power source for electric vehicles and other applications because of their high-energy efficiency, low operating temperature, and zero emissions. Proper water management is required for the operation of PEFCs in order to maintain the critical balance between adequate membrane hydration and prevention of water flooding in the catalyst layer (CL). When a sufficient amount of product water is not removed from the cathode CL, excess water will accumulate and hinder the transportation of oxygen by covering up the reaction sites on the catalyst, causing the cathode to flood and a significant drop in performance, particularly at high current densities. A great number of imaging techniques [4- 7] and measurements of physical indicators [8-11] have been published for monitoring water distribution and flooding in PEFCs. In this paper, the author is the first to report on a method for direct evaluation of water flooding for GDLs by measuring water vapor transport through the GDL. As shown in the Fig. 1, the O2 concentration in the N2 side decreases as the humidity in the O2 side increases, and water flooding is observed when the O2 relative humidity exceeds 43%RH (dew point).