Understanding water management and cathode performance in LT-PEMFCs via EIS and DRT diagnostics

Low-Temperature Proton Exchange Membrane Fuel Cells (LT-PEMFCs) are key to sustainable energy technologies, but their performance is highly dependent on cathode operating conditions and membrane hydration. This study employs Electrochemical Impedance Spectroscopy (EIS) and the Distribution of Relaxation Times (DRT) to analyze the effects of cathode stoichiometry, temperature, cathode feed composition, and hydration levels on key electrochemical processes. The findings highlight the impact of operational parameters on oxygen reduction reaction (ORR) kinetics, proton transport, and mass transport resistance. DRT analysis identifies flooding and membrane drying as dominant performance-limiting phenomena. Pure oxygen feed mitigates mass transport limitations, while variations in air stoichiometry and temperature influence charge transfer resistance and proton conductivity. This study enhances understanding of LT-PEMFC behavior under diverse conditions and provides insights for optimizing performance and durability. The results provide diagnostic features and fundamental insights that can guide the development of future diagnostic frameworks for improved fuel cell control, enhanced water management strategies, and long-term operational stability. • DRT resolved overlapping cathode losses in LT-PEMFCs. • Flooding raised mass transport resistance, drying raised proton losses. • Pure O₂ and higher stoichiometry improved ORR kinetics. • λ ≈ 10⁻⁵ ensured robust and reproducible DRT peak separation.