Relevance of GDL Properties Regarding GDL Quality Assurance

Abstract

Gas diffusion layers are an important part of all types of polymer electrolyte membrane fuel cells (LT-PEMFC, HT-PEMFC or AEMFC). Albeit the conversion reaction is not taking place in the GDL the contributions of the GDL to the function of the cell are essential. So, the GDL needs to homogenise the distribution of reacting gases over the electrode area compensating inhomogeneities created by the channel fin structure of the flow-field of the bipolar plate and at the same time cause a focussing of product streams towards the channels. The GDL needs to conduct electric current between the catalyst layer and the bipolar plate at high current density and transport released thermal energy. The GDL also needs to distribute mechanical pressure of the stack compression.In order to accomplish all those tasks, the GDL needs to feature the right properties with high homogeneity through-out its area and with high reproducibility batch to batch. Unfortunately, a rather high number of properties can be assigned to a GDL. So, the review paper by Yuan et al. on properties for different LT-PEMFC components1 lists about 15 different properties for GDL which influence their function. As many of these properties are difficult to measure measuring all of them is not a viable approach to the quality assurance of GDL as part of their industrial production.Within the project QM-GDL Fraunhofer ICT together with the other partners of the project is analysing the relevance of the different properties, comparing the expected impact of deviation from the designed values and the effort, and determining the actual values. The goal is to determine the most relevant parameters which will allow to assure proper functioning of the GDL if their values are controlled keeping the effort for measurements at a reasonable value.In the presentation the approach for the selection of relevant parameters will be explained at a number of examples. Also, a tentative list of parameters will be presented and discussed.The presented work is part of the project QM-GDL which receives financial support by the German Federal Ministry of Digital Infrastructures and Traffic under Grant Agreement 03B11016E. The content of the presentation is in the sole responsibility of the author. X.-Z. Yuan, C. Nayoze-Coynel, N. Shaigan, D. Fisher, N. Zhao, N. Zamel, P. Gazdzicki, M. Ulsh, K. A. Friedrich, F. Girard and U. Groos, Journal of Power Sources, 491 (2021).