Chemical Oxidation-Induced Degradation in Gas Diffusion Layers for PEFC: Mechanisms and Performance Implications

Gas Diffusion Layers (GDLs) are integral in polymer electrolyte fuel cells, facilitating gas and water transport while providing structural support. However, their susceptibility to chemical degradation significantly impacts their functionality over extensive periods of time. This study investigates the mechanisms of GDL degradation, focusing on chemical oxidation. Accelerated stress testing, which involves immersing GDL in Fenton's reagent for 24 hours, is used. Ex-situ analysis reveals changes in surface properties, including a 3% reduction in contact angle, from 15% to only 9% remaining fluorine on the surface, and OH group presence in GDLs exposed to Fenton's reagent. In-situ methods are used to study the impact of GDL degradation on fuel cell performance. Polarization curve reveals a 17% performance enhancement in aged GDLs, with a corresponding 19% decrease in voltage loss due to oxygen transport resistance at a high current observed via transient limiting current analysis. Electrochemical impedance spectroscopy reveals a 51% reduction in mass transport resistance, providing insights into structural alterations, such as pore widening and increased hydrophilicity. Despite these improvements, aged GDL demonstrates substantial degradation under high humidity, leading to water management challenges and voltage instability. This is attributed to the loss of fluorine, as indicated by the ex-situ analysis