Hydrophilic and hydrophobic double MPL coated gas diffusion layer to prevent drying-up and flooding of polymer electrolyte fuel cells

Gas diffusion layers (GDLs) coated with a hydrophobic microporous layer (MPL) have been commonly used to improve water management properties of polymer electrolyte fuel cells (PEFCs). In the present study, a novel hydrophilic and hydrophobic double MPL coated GDL was developed to achieve further enhancement of the PEFC performance under both low and high humidity conditions. Under low humidity conditions, a thin hydrophilic layer using titanium dioxide coated on the hydrophobic MPL is effective to conserve the humidity of the membrane electrode assembly (MEA), while a hydrophobic intermediate MPL between the hydrophilic layer and the carbon paper substrate prevents removal of water in the hydrophilic layer. This results in a significant enhancement of the ability of the MPL to prevent drying-up of the MEA. Under high humidity conditions, the double MPL coated GDL with appropriate pore diameter, thickness, and hydrophilic and hydrophobic properties is also effective to reduce flooding on the cathode catalyst layer, resulting in the higher PEFC performance compared with that for a hydrophobic MPL coated GDL.