Wettability characterization of pore networks of gas diffusion layers in proton exchange membrane fuel cells

Both the structure of the pores in a Gas diffusion layer (GDL), and the interactive characteristics between water and the carbon fibers which compose the GDL are very important in understanding transport phenomena in Proton exchange membrane fuel cell (PEMFC), especially water transport, distribution and management. Wettability of pore network as well as its structure is the major factor which determines the relation between water or air saturation and capillary pressure of the micro-scale pore network. In this study, the impregnation characteristics of TGPH-120 with 30 wt.% of PTFE as a function of time were investigated at different temperature to determine the effect of water condensation in the pore network. In succession, using the Method of standard porosimetry (MSP), various porometric characteristics are suggested. The proportion of saturated pore volume with water to the total pore volume is represented for the GDL impregnated at different temperatures. The contact angle of water on the hydrophilic pores whose size is in charge of a majority of the pore volume was estimated from 35° to 53°. The relation of capillary pressure with saturation was also measured for each condition. The air saturation increased slower with increasing capillary pressure when water was used as the working liquid than when octane was used because of the mixed wettability of the pore networks in the GDL.