Gas diffusion layer wettability determination by cyclic voltammetry for automotive fuel cells

Abstract

AbstractFuel cell performance and durability are highly dependent on water management, wherefore wettability properties of the cell's gas diffusion layer (GDL) are important. In this work, we implement a method to determine the GDL wetted surface area, which is based on capacitance measurements by cyclic voltammetry with a pH‐neutral, aqueous electrolyte, to an automotive size fuel cell failure analysis process and demonstrate its benefit. The electrolyte penetrates large pores of the GDL, wherefore, in contrast to the most conventional methods, also inner parts of the GDL are measured. Tenside concentration of the electrolyte and penetration time, polytetrafluoroethylene treatment of the GDL, and properties of the microporous layer highly influence the capacitance values. Thus, the method is sensitive to different GDL morphologies and surface modifications. Different degradation patterns for samples either artificially chemically and mechanically aged or after real‐operation (e.g., prototype vehicle) are detected by the method. For a comprehensive understanding, the obtained results are compared to ex situ degradation analysis data. A comparison to static contact angle measurements, being a state‐of‐the‐art method to determine GDL wettability, reveals a higher sensitivity of the introduced method to detect degradation, in particular, of chemically aged and real‐operation aged GDLs.