Influence of Hydrophilic and Hydrophobic Double MPL Coated GDL on PEFC Performance without Cathode Humidification

Abstract

Gas diffusion layers (GDLs) coated with a hydrophobic microporous layer (MPL) have been commonly used to improve the water management properties of polymer electrolyte fuel cells (PEFCs). In the present study, a new hydrophilic and hydrophobic double MPL coated GDL was developed to achieve further enhancement of PEFC performance without cathode humidification. A hydrophobic binder of polytetrafluoroethylene (PTFE) and a hydrophilic binder of polyvinyl alcohol (PVA) were used to coat the MPL on the carbon paper substrate. The hydrophilic layer is effective for conserving humidity at the catalyst layer, while the hydrophobic intermediate layer between the hydrophilic layer and the substrate prevents the removal of water in the hydrophilic layer via dry air in the substrate. Reducing the hydrophilic layer thickness to 5 μm was effective for enhancing PEFC performance. Appropriate enhancement of hydrophilicity by increasing the PVA content to 5 mass% was also effective for enhancing PEFC performance.