Influence of the water uptake in the catalyst layer for the proton exchange membrane fuel cells

• Water-uptake decrease by the Nafion thin film in the CL was measured using DVS.
• Model accuracy at low RH drastically increased by using modified water uptake.
• Model was validated by comparing I–V curves of both 100% and 20% RH.
• Severe performance drop was obtained as RH decreases, which satisfy the experiments.

Previously, mathematical modeling of a proton exchange membrane fuel cell has failed to precisely predict the performance in low relative-humidity operations. Herein, we report the fit parameters for water-uptake isotherm of the catalyst layer based on experimental measurements of dynamic vapor-sorption (DVS) technique. From the DVS measurement, it is revealed that the Nafion ionomer in the catalyst layer holds approximately 2.94 times lower water uptake than the Nafion membrane. By integrating this relation to the macroscopic model, the performance decrease due to the anode dehydration is appropriately captured relative to the previous model. Influences of the relative humidity on cell performance have been further investigated to correct the misguided prediction from the previous model.