Effect of cathode catalyst layer on proton exchange membrane fuel cell performance: Considering the spatially variable distribution

Abstract

The effect of the ionomer spatial distribution in the cathode catalyst layer (CCL) of the proton exchange membrane fuel cell (PEMFC) on oxygen and proton transport has been extensively studied. However, models generally assume a mean spatial distribution (MSD) of ionomer, and consideration of the actual spatial distribution (ASD) is indeed insufficient. In this study, a multi-dimensional PEMFC model is developed to investigate the effect of ionomer ASD versus MSD on cell performance. In addition, we corrected the Damkohler number (Da) by taking into account the local oxygen transport interfacial resistance and catalyst parameters into δ (an effective ionomer thickness), which allows Da to more accurately reflect the oxygen supply. The results show that the MSD assumption for ionomer tends to underestimate cell performance at the same current density. The proton transport resistance of ASD is 3.17% higher than that of MSD, but the oxygen concentration is 42.8% larger. This is mainly attributed to the larger porosity and lower saturation near the CCL/CMPL interface in the ASD model, which facilitates oxygen transport. The Da sufficiently supports the results, and the Da at the CCL/MPL interface of the ASD model (0.34) is smaller than in the MSD model (0.82), indicating relative oxygen enrichment. This study provides guidance for future PEMFC models.