Analysis of performance stability under conditions of high & low humidity of polymer electrolyte fuel cells with interdigitated gas flow channels formed on a gas diffusion layer: An X-ray imaging and modeling study

Recently, a new concept was developed for the design of polymer electrolyte fuel cells, based on a flat, solid separator and a porous GDL with interdigitated gas-flow channels. This newly designed cell has demonstrated the ability to overcome the principal issues of the conventional design, in which the interdigitated flow channels are formed on the separator; the latter can experience low performance under high and low humidity conditions. In the present study, we have sought to reveal the mechanism of the performance stability improvement. The temperature and gas flow distributions are calculated by numerical simulation, and the water distribution is visualized by X-ray imaging. From these results, the porous ribs in the newly designed cell are found to play several important roles as follows: under conditions of excess water, the porous ribs help to alleviate water accumulation in the GDL by acting as a reservoir for excess water and also by increasing the temperature in the GDL; and, under conditions of water shortage, the porous ribs alleviate the dry-out of the GDL by withdrawing water from the reservoir and also by decreasing the rate of gas flow forced through the GDL.