Numerical Study of Mass Transport and Electrochemical Kinetics inside Porous Structure Layers of PEMFC Using Direct Simulation Approach

Abstract

The enhancement of the mass transports in porous layers of a polymer electrolyte fuel cells (PEFCs) is essential for developing material and design system to improve the PEFC performance and durability. The oxygen transport resistance is a large fraction of the mass-transport overpotential at the cathode. Condensed water in the flow field and porous layers reduces oxygen transport to the oxygen reduction reaction (ORR) region. Experimental investigation of locally saturated porous media in the operating cell is difficult. The Computational Fluid Dynamics (CFD) is mathematical modeling tool, which can be considered the incorporation of theory and experimentation in the field of kinetics, heat, and mass transport of the PEFCs. The purpose of this work is to use direct modeling-based, Lattice Boltzmann Method (LBM) within the detailed structure of porous layers to understand the kinetics and multi-scalar/multi-physics transports in a polymer electrolyte fuel cells (PEFCs). The model geometries consist of gas diffusion layer (GDL), micro porous layer (MPL), and Catalyst layer (CL), as shown in Fig. 1. The studies include the understanding of water evolution, water saturation, breakthrough pressure, heat transfer, species transport, and electrochemical kinetics inside porous layers under different conditions and situations that could occur in fuel cells. This work will show the enhancement of direct CFD simulation with LBM (CFD-LBM) approach [1-4], which incorporates with detailed structure of porous and catalyst layers from both micro- and nano- X-ray CT. This approach will consist of the kinetic model in the catalyst layer, which will involve coupling electrochemical kinetic to investigate the electrical potentials, electrical current, electron transfer, and exchange current in the catalyst layers, as shown in Fig. 2. The output of this work will be used for the optimization of catalyst layer thickness, with durability and water management improvement, for novel porous materials, particularly in the catalyst layer. References: P. Satjaritanun, S. Hirano, A. D. Shum, I. V. Zenyuk, A. Z. Weber, J. W. Weidner, and S. Shimpalee, Journal of the Electrochemical Society, 165 (13), (2018) F1115-F1126. P. Satjaritanun, J.W. Weidner, S. Hirano, Z. Lu, Y. Khunatorn, S. Ogawa, S.E. Litster, A.D. Shum, I.V. Zenyuk, S. Shimpalee, Journal of the Electrochemical Society, 164 (11), (2017) E3359-E3371. S. Shimpalee, S. Hirano, M. DeBolt, V. Lilavivat, J.W.Weidner, Y. Khunatorn, Journal of the Electrochemical Society, 164(11), (2017) E3073-E3080. S. Shimpalee, V. Lilavivat, H. Xu, J. R. Rowlett, C. Mittelsteadt, and J. W. Van Zee, Journal of the Electrochemical Society, 165 (11), (2018) F1019-F1026. Figure 1