Pore Network Modeling of Microporous Layers for Polymer Electrolyte Fuel Cells

Liquid water accumulated in the catalyst layer (CL) and gas diffusion layer (GDL) of a polymer electrolyte fuel cell (PEFC, PEMFC) results in performance deterioration due to inhibition of oxygen transport to the cathode CL (Flooding). To enhance the drainage in the GDL, the application of a microporous layer (MPL) is effective to the CL side of the GDL substrate [1, 2]. To elucidate the effects of two-phase flow on the oxygen transport in an MPL for its optimized designs, we model three dimensional porous structures of in-house MPLs with pore network model (PNM) [3, 4] for convective air permeation and oxygen diffusion. Pore diameter distribution derived by a focused ion beam scanning electron microscope (FIB-SEM) is employed in the PNM. Air permeation measurements combined with oxygen diffusion measurements with changing wetting liquid saturation (Galwick, Porous Materials Inc., USA) by using gas chromatography validate the model. Acknowledgments The authors are indebted to graduate students, Messrs. Yuhang Liu, Kentaro Harano, Dingfeng Chen for help in the modeling and experiment. Thanks are offered to Professor Kohei Ito of Kyushu University for valuable discussions. The authors acknowledge Ms. Chie Uryu of International Research Center for Hydrogen Energy, Kyushu University for operating the FIB-SEM. References Nakajima H, Konomi T and Kitahara T. 2007. Direct water balance analysis on a polymer electrolyte fuel cell (PEFC): Effects of hydrophobic treatment and micro-porous layer addition to the gas diffusion layer of a PEFC on its performance during a simulated start-up operation. Journal of Power Sources 171: 457-463. Kitahara T, Konomi T and Nakajima H. 2010. Microporous layer coated gas diffusion layers for enhanced performance of polymer electrolyte fuel cells. Journal of Power Sources 195: 2202-2211. Gostick J, Aghighi M, Hinebaugh J, Tranter T, Hoeh MA, Day H, Spellacy B, Sharqawy MH, Bazylak A, Burns A, Lehnert W and Putz A. 2016. OpenPNM: A pore network modeling package. Computing in Science & Engineering 18: 60-74. http://openpnm.org/. Accessed on September 14, 2020