Bypassing the Jam: How GDLs with Engineered Water Highways Can Re-Enable Interdigitated Flow Fields for PEFCs

Abstract

The use of interdigitated flow fields in polymer electrolyte fuel cells (PEFCs) was originally proposed in the 90’s by Nguyen (1), and can lead to a significant reduction of mass transport losses due to the fact that oxygen is not transported by diffusion, but by convection under the flow field lands (2). However, the same authors reported a few years later (3) that this type of flow field introduces significant cell-to-cell flow distribution issues when placed in a stack arrangement. With the help of neutron imaging, several authors (4-6) have identified the accumulation of water at the end of the inlet channels and the related increase in pressure drop as a major contribution to this problem. Here, we will present a novel solution to this problem on the basis of our previously developed gas diffusion layers featuring patterned wettability (7). Hydrophilic lines are used to create a bypass for water without altering the mechanical structure of the GDL – which would produce a bypass for gases in dry conditions. Experiments conducted on a 12 cm2 cell and with gas flow stoichiometries as low as 1.4 demonstrated an outstanding improvement in comparison with a standard, fully hydrophobized material. Besides the stable performance, the increase of pressure drop is moderate and nearly constant in comparison with the much larger and unpredictable pressure drop obtained with a conventional GDL. Neutron imaging confirmed that this difference is due to the water accumulation in the gas flow channels with a commercial material – which is fully avoided thanks to the hydrophilic highways in the patterned material (see Figure 1). The moderate and stable pressure drop of our proposed design is highly promising, as it will likely solve the cell-to-cell flow distribution issue in a stack configuration. References T. V. Nguyen, Journal of The Electrochemical Society, 143, L103 (1996). K. Tajiri, J. Karani and U. N. Shrivastava, Journal of The Electrochemical Society, 165, F1385 (2018). T. Van Nguyen and M. W. Knobbe, Journal of Power Sources, 114, 70 (2003). N. J. Cooper, A. D. Santamaria, M. K. Becton and J. W. Park, Energy Conversion and Management, 136, 307 (2017). D. Kramer, J. Zhang, R. Shimoi, E. Lehmann, A. Wokaun, K. Shinohara and G. G. Scherer, Electrochimica Acta, 50, 2603 (2005). J. P. Owejan, T. A. Trabold, D. L. Jacobson, D. R. Baker, D. S. Hussey and M. Arif, International Journal of Heat and Mass Transfer, 49, 4721 (2006). A. Forner-Cuenca, J. Biesdorf, L. Gubler, P. M. Kristiansen, T. J. Schmidt and P. Boillat, Advanced Materials, 27, 6317 (2015). Figure 1