Study on Performance Stability Improvement of Polymer Electrolyte Fuel Cells with Interdigitated Gas Flow Channels on a Gas Diffusion Layer
Authors: Inoue Tatsuya , Sakai Daiki , Hirota Kazuyuki , Sano Koichi , Hirayama Naoki , Nasu Mitsunori , Suzuki Takahiro , Tsushima Shohji , Inukai Junji , Watanabe Masahiro , Iiyama Akihiro , Uchida Makoto 
Published: December 2024

Recently, a new concept was developed for the design of polymer electrolyte fuel cells, combined a flat separator and a porous gas diffusion layer (GDL) with interdigitated gas-flow channels.1 This new design cell has demonstrated higher performances than that of a conventional cell combined a solid separator with serpentine flow-channels and a flat GDL.2 Conventional interdigitated flow-channel designs, which consist of a solid separator with interdigitated gas-flow channels and a flat GDL, have been known for their higher efficiency of the oxygen supply to the catalyst layer, in comparison with serpentine or parallel flow-channels in combination with a flat GDL, because of the forced convection of the supplied gas in the GDL. However, conventional interdigitated flow-channels have faced two issues associated with low performance: one occurs under high-humidity conditions because of nonuniform gas flow due to accumulated water in the GDL; the other is caused by forced water discharge from the GDL under low-humidity conditions.
In this study, to investigate the possibility of the new cell design to overcome such performance issues of conventional interdigitated cells, both conventional and new cell designs were tested with single cells of 1 cm2 active area, and the performances were compared at high and low humidity with various conditions of gas supply. From these results, we have found that the new design of the GDL with interdigitated channels has a clear advantage over that of the conventional separator with interdigitated channels, being able to maintain higher performance under conditions of both water excess and water shortage.3

To reveal the mechanism of the improvement in the cell performance, the temperature and gas flow distributions in the GDL of the new and the conventional interdigitated cells were calculated by numerical simulation, and the water distribution was visualized by X-ray imaging.4 From comparisons of these experimental and numerical results in the two cells, the porous ribs in the newly designed cell were found to play several important roles, as follows: under conditions of excess water, the porous ribs with relatively low thermal conductivity 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 adjacent to the catalyst layer; and, under conditions of water shortage, the porous ribs help to alleviate the dry-out of the GDL by withdrawing water from the reservoir shortly and also by decreasing the rate of gas flow forced through the GDL because the porous ribs act as the short-cut pathway for the gas flow.
Based on these mechanistic and performance analyses, it is becoming clearer that the new cell design, with interdigitated flow-channels and porous ribs, has the potential to overcome the performance issues of conventional interdigitated cells.

Acknowledgement

This work was partially based on results obtained from project JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

References

Watanabe et al., J. Electrochem. Soc., 166, F3210 (2019).

Nasu et al., J. Power Sources, 530, 231251 (2022).

Inoue et al., J. Electrochem. Soc., 169, 114504 (2022).

Inoue et al., J. Power Sources, 585, 233623 (2023).

Figure 1