Increased performance of PEFCs with engineered mass-transport pathways

The present experimental study investigates the introduction of laser-cut perforations designed to create engineered pathways for improved gas and liquid transport in the diffusion media (DM) of polymer electrolyte fuel cells (PEFCs). Conceptually, the perforations allow for increased gas and vapor access to the catalyst layer (CL) at low current, and at high current they act as water conduits for removing excess liquid water. If not properly engineered, however, perforations lead to excessive flooding or dryout, depending on the conditions. The effect of perforation diameters of 100 μm and 300 μm was studied using steady state polarization testing, electrochemical impedance spectroscopy (EIS), and limiting current analysis. Each of these experimental methods lends insight into the observed performance changes between the different cells. It was found that perforations are beneficial under low-humidity conditions, increasing the limiting current by up to 7% compared to the unaltered DM. Optimization of the perforation diameter is critical to produce similarly beneficial results with high-humidity conditions.