A double-stage process-impedance-assisted model to investigate the water behavior at the cathode triple phase boundary for degraded PEMFC

Excessive water on the cathode triple phase boundary (TPB) in proton exchange membrane fuel cells (PEMFCs) hampers oxygen reduction reaction and accelerates catalyst layer degradation, impacting performance and lifespan. Thus, investigating water behavior at the TPB is vital for prolonging PEMFC lifespan. However, a degradation-considered approach without visualization equipment remains a challenge. To overcome this challenge, this paper proposes a double-stage model considering PEMFC degradation to estimate the water content on the cathode TPB. In the first stage, the aging parameters of the catalyst layer (CL), gas diffusion layer (GDL), and membrane are considered, except for the membrane thickness. In the second stage, the degradation of the membrane thickness is further incorporated, considering its significant decay. The model is verified using experimental data from a single cell and a degraded stack and applied to analyze the water behavior at the TPB of PEMFC. Results suggest that at 810 h, water content is 8.75 at 1.0 A/cm2, lower than 10.07 at 0.4 A/cm2 due to severe CL degradation. Furthermore, the study reveals that the cathode transfer coefficient, a crucial parameter for cathode kinetics, is influenced by both the electrochemically active surface area (ECSA) and the water content on the cathode TPB.