Study of Liquid Water Breakthrough Process in the Gas Diffusion Layer of Proton Exchange Membrane Fuel Cells

The relationship between the liquid water breakthrough process in the gas diffusion layer (GDL) of the proton exchange membrane fuel cell (PEMFC) and the structure of the GDL is investigated, and the pressure and droplet morphology of liquid water passing through the GDL are investigated; the surface wettability and microstructure of the GDL are analyzed by using a contact angle meter and a scanning electron microscope (SEM). A liquid water breakthrough GDL visualization test platform is built to investigate the effects of inlet flow rate, GDL thickness, microporous layer (MPL), and polytetrafluoroethylene (PTFE) on the process of liquid water breakthrough GDL. The results show that the carbon paper diffusion layer has a larger surface contact angle. The internal carbon paper diffusion layer consists of fibers interwoven into a tight mesh structure, and the carbon cloth diffusion layer presents a loose fiber arrangement structure. The pressure of liquid water gradually increases with time, and when it reaches the pressure limit, it will rapidly decrease and maintain near the stable pressure. The larger the inlet water flow rate is, the smaller the breakthrough pressure is. The GDL thickness increases by 1.9 times, and the breakthrough pressure increases by 63%. The liquid water breakthrough pressure of MPL-coated GDL is 3.6 times higher than that of uncoated. The addition of 30[Formula: see text]wt.% PTFE increased the liquid water breakthrough pressure.