<p>Enhancing mass transport is critical for improving PEMFC performance, especially at high current densities where reactant delivery and water removal become limiting. The gas diffusion layer (GDL) plays a central role in these processes. In this study, we introduce a novel, patterned GDL designed to boost reactant transport and facilitate water removal. The patterns are placed in regions with lower inter-channel pressure differentials—where reactant concentration is typically more uniform—and are applied to a PEMFC with a serpentine flow field. While we anticipate that GDL patterning will significantly enhance mass transport, it may also shorten electron conduction pathways and increase ohmic losses. To assess these competing effects, we compare cell performance metrics before and after patterning, examining how improved mass transport balances against any rise in ohmic resistance. We also evaluate liquid saturation and oxygen concentration at the cathode GDL–catalyst interface to clarify their impact on overall performance. The objective of this work is to develop an optimized GDL design that maximizes mass transfer and water removal while minimizing additional ohmic losses, thereby achieving superior PEMFC performance.</p>