Neutron imaging of generated water inside polymer electrolyte fuel cell using newly-developed gas diffusion layer with gas flow channels during power generation

To accelerate the spread use of polymer electrolyte fuel cells (PEFCs), it is essential to increase power density and durability, while reduce costs. We have succeeded in developing an innovative gas diffusion layer (GDL) with gas flow channels (GDLFC+) fabricated on a flat separator that enabled both cost reduction and high performance. In this study, neutron radiography was used to observe the distribution of liquid water during power generation (1–3 A cm−2) of a cell with a size (1.0 cm (W) x 9.7 cm (L)) large enough to evaluate the actual cell. With using our GDLs and interdigitated (comb-shaped) gas flow channels, the distributions of liquid water were quantitatively imaged, influenced by the current density, the relative humidity, the oxygen utilization, and the water repellency of the GDL. The increase in linear velocity of the oxidant gases effectively suppressed the retention of liquid water at the cathode. Even at high oxygen utilization (67%) under continuous power generation for 30 min, the water-repellent GDL effectively made possible the back-diffusion of water over the entire electrode area, contributing not only to a large reduction in diffusion overvoltage but also in Ohmic overvoltage, resulting in high current density and high stability of a PEFC.