Novel hydrophilic and hydrophobic double microporous layer coated gas diffusion layer to enhance performance of polymer electrolyte fuel cells under both low and high humidity

A novel hydrophilic and hydrophobic double microporous layer (MPL) coated gas diffusion layers (GDL) was developed to enhance the performance of polymer electrolyte fuel cells (PEFCs) under both low and high humidity. A thin hydrophilic layer using titanium dioxide (TiO₂) coated on the hydrophobic MPL is effective at conserving the humidity of the membrane electrode assembly (MEA) under low humidity, while a hydrophobic intermediate MPL between the hydrophilic layer and the carbon paper substrate prevents the removal of water from the hydrophilic layer. This results in a significant enhancement of PEFC performance under low humidity over that for a conventional hydrophobic MPL coated GDL. The double MPL coated GDL is also effective at increasing the discharge of excess water from the catalyst layer, which reduces flooding and achieves further enhancement of the PEFC performance under high humidity, compared with that for a conventional hydrophobic MPL coated GDL. The appropriate pore diameter and hydrophobicity, and decrease in the thickness of the hydrophobic intermediate MPL in the double MPL, are essential to enhance the PEFC performance.