Influence of ptfe content in microporous layer coated gas diffusion layer on hydrophobicity and pefc performance

Gas diffusion layers (GDLs) coated With a microporous layer (MPL) have been commonly used to improve the water management property of polymer electrolyte fuel cells (PEFCs). In the present study, the influence of the PTFE content in the MPL on hydrophobicity and PEFC performance was evaluated. The maximum pore diameter of the GDL was measured using an air permeability test apparatus in which a low surface tension wetting liquid filled the pores of the GDL. A water permeability test was also carried out using the same apparatus. When the maximum pore diameter measured using the water permeability test was assumed to be the same value as that measured using the air permeability test, the contact angle inside the GDL pore could be accurately estimated. Increasing the PTFE content in the MPL extends the contact angle, which enhances the hydrophobic property of the GDL. Under low humidity conditions, decreasing the PTFE content is effective for preventing drying-out of the MEA, enhancing PEFC performance. Under high humidity conditions increasing the PTFE content to 20 mass% is effective for preventing flooding, enhancing PEFC performance. However, when the PTFE content becomes too high, PEFC performance tends to decrease.