Imaging of generated water using neutron radiography in a newly-developed polymer electrolyte fuel cell during power generation

To accelerate the spread use of polymer electrolyte fuel cells (PEFCs), it is essential to increase power density and durability, while reducing costs. We have succeeded in developing an innovative gas diffusion layer (GDL) with gas flow channels (GFCs) named '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 at 1-3 A cm^-2 in a cell with a size of 1.0 cm (W) x 9.7 cm (L) large enough to evaluate the actual cell. With using our GDLs and interdigitated (comb-shaped) GFCs, the distributions of liquid water were quantitatively imaged, influenced by the current density, the relative humidity, 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. 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. (author)