Water droplet detachment characteristics on surfaces of gas diffusion layers in PEMFCs

Water management is one of the key issues affecting the performance and stability of proton exchange membrane fuel cells (PEMFCs). Water detachment on the gas diffusion layer (GDL) surface is critically important to water management in PEMFCs. In this study, water droplet detachment characteristics under various GDL surface contact angles and channel heights are investigated, by using a customized transparent model cell for direct ex-situ water visualization. The droplet height, chord, height/chord ratio, and contact angle hysteresis at the instant of droplet detachment are quantitatively analyzed. The droplet detachment is easier for higher gas Reynolds number (Re-g). The height and chord of the droplet both decrease with Re-g for both GDLs with and without PTFE but their decrement rates become smaller in higher Re-g regions for all the channel heights investigated. Compared with droplets on the untreated GDL, the droplet height/chord ratio on the PTFE-treated GDL with larger static contact angle is increased by 36.7%, 64.1% and 76.0% and the contact angle hysteresis is reduced by 17.1%, 16.3% and 12.6% for the channel height H of 1 mm, 2 mm and 3 mm, respectively, which indicates that the PTFE-treated GDL improves water detachment. It shows that the water detachment is improved by reducing the channel height due to the smaller contact angle hysteresis at the instant of droplet detachment. (C) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

Water management is crucial for the performance and stability of proton exchange membrane fuel cells (PEMFCs). This study investigates the detachment characteristics of water droplets on the gas diffusion layer (GDL) surface under different contact angles and channel heights. The results show that droplet detachment is influenced by the gas Reynolds number and the presence of PTFE on the GDL surface. The study also suggests that reducing the channel height can improve water detachment.