Development and impact of sandwich wettability structure for gas distribution media on PEM fuel cell performance

Water management is one of the key issues related to the performance, durability and cost of polymer electrolyte membrane fuel cells (PEMFCs); and the wettability of gas distribution media (GDM) is critical to the water management. In this study, a novel design is developed for GDM, referred to as sandwich wettability GDM. After being coated with a silica particle/poly(dimethylsiloxane) (PDMS) composite, the GDM has superhydrophobic surfaces with a contact angle of 162 ± 2°, but hydrophilic internal pores. Water droplets (10 μl) can roll off the tilted surface of the coated GDM at an angle of 5°, and can also be drawn into the pores of the coated GDM in 10 min when it is horizontal. The surface morphology, roughness and pore structures of GDMs are characterized by profilometry, scanning electron microscopy, and porosimetry. The measured internal pore size of the coated GDM is around 7.1 μm, and shows low energy resistance to gas transport. Performance testing indicates that the PEMFC equipped with sandwich wettability GDMs offers the best performance compared to those with raw GDM (untreated with surface coating), conventional GDM (with microporous layer) coated with PTFE or hydrophilic GDM (coated with silica particles).