Study on the Relationship between GDL Wettability and Liquid Water Behavior in Polymer Electrolyte Fuel Cells

Abstract

Liquid water that accumulates inside gas diffusion layers (GDL) prevents oxygen transport and degrades the performance of polymer electrolyte fuel cells (PEFCs). Therefore, improving the drainage of GDL is neccesary. One factor that directly affects drainage is the wettability of GDLs. In this study, the relationship between wettability of GDL and drainage was investigated through a numerical simulation using the volume of fluid (VOF) method. The simulation incorporated condensation model to mimic the actual operation of a PEFC. As a result of the simulation, it was found that condensation occurs near the catalyst layer (CL), and that liquid water accumulation develops from the vicinity of the CL side to the channel side. Simulations for different contact angles of θ contact = 60°, 90°, 110°, and 150° were performed, and showed that the liquid water volume inside the GDL decreased in the case of higher contact angle. In addition, we found that the hydrophobicity of the GDL promotes the movement of liquid water and hastened liquid-water discharge from the GDL surface. In the case of higher contact angle, the proportion of the gas-liquid interface in the GDL and its curvature were found to increase. Furthermore, the liquid water was discharged from greater number of pores on the GDL surface.