Precisely Designed Hydrophilic Networks in Microporous Layer for High Performance of Proton Exchange Membrane Fuel Cells

Proton exchange membrane fuel cell (PEMFC) is considered the next promising generation of power devices for vehicles. The microporous layer (MPL) improves the performance through effective water management. In this study, local hydrophilic networks of nano- and macropores are formed in different MPLs. The measured internal contact angle to water confirms that Vulcan carbon black (VB) is helpful for the formation of hydrophilic pores. The MPL sample containing 10% VB (P1-H) exhibits the best performance under a wide range of humidities. Its peak power density reaches 1.51 W/cm2 under 60% relative humidity (RH) and drops only 1.99% under 80%RH. As shown in the three-dimensional simulation model, the hydrophilic nanopores preferentially serve as water reservoir regions to ensure a certain amount of water for membrane hydration and control the water droplet size at the interface. The ohmic resistance and mass transfer resistance of P1-H are reduced under a high current density. The MPL containing hydrophilic macropores (P3-H) displays a slight performance improvement. Despite enhanced air permeability, hydrophilic macropores directly drain water and result in membrane dehydration. The findings provide an optimized strategy for the precise design of MPL to achieve high performance and adaptation under a wide range of humidity.