Measurements of bulk and contact thermal resistances of PEMFC gas diffusion and microporous layers

The thermal conductivity and thermal contact resistance of gas diffusion layer (GDL) and microporous layer (MPL) are key parameters that affect the performance of proton exchange membrane fuel cells. Conflicting results were reported in previous studies, including the effect of PTFE (Polytetrafluoroethylene) on the GDL effective thermal conductivity, and the magnitude of the thermal contact resistance between the GDL substrate and the MPL coating. In view of this, the two-thickness method is used to measure the thermal conductivity and the thermal contact resistance of a Toray GDL with a MPL coating. The results show that when the loading pressure is increased from 0.25 MPa to 2 MPa, the effective thermal conductivity of the GDL increases from 1.22 W m−1 K−1 to 1.81 W m−1 K−1, while the effective thermal conductivity of the MPL coating remains unchanged at 0.5 W m−1 K−1. Treatment with 20 wt% PTFE reduces the effective thermal conductivity of the GDL by 25%. The thermal contact resistance between the GDL substrate and the MPL coating accounts for only 6.35% of the total thermal resistance of the GDL-MPL components, indicating that this thermal contact resistance is not a major factor in the PEMFC design.