Comprehensive analysis of PTFE distribution in gas diffusion layers using advanced ex-situ and in-situ characterization techniques

Sammanfattning

The performance and longevity of Proton Exchange Membrane Fuel Cells (PEMFCs)are critically dependent on the properties of the gas diffusion layer (GDL).This study investigates the hydrophobic treatment using the dip coating methodon two types of GDLs, namely dry-laid and wet-laid, using polytetrafluoroethylene(PTFE) at target concentrations of 5 wt%, 20 wt%, and 50 wt%. The distributionof PTFE across the thickness and surface of the GDLs is characterized tounderstand its impact on water management and gas transport properties. The effectivenessof the hydrophobic treatment is evaluated both ex-situ via contact anglemeasurements and in-situ by limiting the current density to assess oxygen transportresistance. Additionally, advanced characterization techniques, including ScanningElectron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), and RamanSpectroscopy, are employed to provide a detailed analysis of PTFE distribution,correlating these findings with the GDL’s performance in operating PEMFCs.**Key findings** reveal that while increased PTFE concentration improved hydrophobicityand water management, excessive PTFE loading led to pore blockage,negatively impacting oxygen transport resistance. The wet-laid GDL demonstratedmore uniform PTFE distribution and higher transport resistance compared to thedry-laid GDL. These insights emphasize the importance of balancing PTFE concentrationto optimize both water management and gas diffusion in PEMFCs.