Laser perforated fuel cell diffusion media. Part I: Related changes in performance and water content

In this study, cathode-side, bi-layered diffusion media (DM) samples with micro-porous layer were perforated with 300 μm laser-cut holes (covering 15% of the surface area in a homogenous pattern) using a ytterbium fiber laser to investigate the effect of structural changes on the gas and water transport. Under reduced humidity conditions (50% inlet relative humidity on the anode and cathode), the perforated DM were observed to increase the potential by an average of 6% for current densities ranging from 0.2 to 1.4 A cm−2. However, the perforated DM showed reduced performance for current densities greater than 1.4 A cm−2 and at all currents under high-humidity conditions. Neutron radiography experiments were also performed to understand the changes in liquid water retention characteristics of DM due to the laser perforations. Significant water accumulation and water redistribution were observed in the perforated DM, which helps explain the observed performance behavior. The results indicate that the perforations act as water pooling and possible channeling locations, which significantly alter the water condensation, storage, and transport scheme within the fuel cell. These observations suggest that proper tailoring of fuel cell DM possesses significant potential to enable fuel cell operations with reduce liquid overhead and high performance.

► This study tests diffusion media (DM) with 300 μm diameter perforations in a PEFC.
► 300 μm diameter DM perforations had a 6% increase in performance with low humidity.
► Severe performance degradation of the perforated DM is observed with high humidity.
► Modes of water transport mechanisms of perforated and unaltered DM are discussed.
► A technique to experimentally determine Fickian diffusion changes is presented.