Laser Perforated fuel cell diffusion media: Engineered interfaces for improved ionic and oxygen transport

The purpose of this work is to explore engineered interfacial and structural architecture in fuel cell diffusion media (DM). Perforations were introduced via lasers on samples of virgin DM that contained hydrophobic content. Depending on laser choice, some lasercut samples displayed a "heat affected zone" (HAZ) at the catalyst layer I microporous layer interface, characterized by a region surrounding each perforation where hydrophobic content was removed. At 50% inlet relative humidity, DM with homogeneously dispersed 100-μm perforations and a HAZ displayed a 25% power density increase compared to virgin DM. Analyzing the oxygen concentration dependence in the double-Tafel region showed transport resistances were dominated by oxygen at moderate current values. Electrochemical impedance spectroscopy (EIS) and neutron radiography results indicated charge- and mass-transport impedances and liquid water redistribution play an important role, depending on the operating current density. Results suggested two mechanisms for the increased performance of the 100-μm DM with HAZ: l) liquid water storage and through-plane water redistribution led to rehydration of the catalyst layer and membrane, and ll) in-plane water redistribution led to improved oxygen transport through the DM. The results of this study shed light on the importance of interfacial and structural architecture of fuel cell DM.