(Industrial Electrochemistry and Electrochemical Engineering Division H. H. Dow Memorial Student Achievement Award) Transport Study Inside Porous Layers of PEFC Using Direct Numerical Simulation
The purpose of this work is to use direct modeling based Lattice Boltzmann Method (LBM) [1-4] to understand the multi-scalar/multi-physics transports of various porous layers in a polymer electrolyte fuel cells (PEFCs). 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. Condensed water in the flow field and porous layers reduces oxygen transport to the oxygen reduction reaction region. Current platinum group metal (PGM) catalysts tend to experience transport resistance, which results in kinetic limitations within the hydrogen oxidation reaction (HOR) and the oxidation reduction reaction (ORR). Due to these limitations, the enhancement of mass transport is critical to improving fuel cell performance and durability, and therefore the development of a PGM-free catalyst is vital in understanding multi-scalar transport. This will enrich the development of novel structures that address local oxygen transport resistance in the PGM-free catalyst layer, and will outline the urgent need to further investigate multi-physical phenomena and the electrochemical nature of a fuel cell. The model geometries of porous layers [gas diffusion layer (GDL), micro porous layer (MPL), and catalyst layer (CL)] provided in this study were obtained by a 3D, reconstructed microstructure from both micro and nano X-ray computed tomography (CT) as shown in Figure 1. Current research outcomes reveal that the liquid water saturation profiles inside the GDL, breakthrough pressures, heat, and mass transport are dependent on GDL type, operating conditions, cell assembly specifications, and flow field geometry [3]. This work also shows the enhancement of my approach that include the kinetics model in the catalyst layer, which will involve coupling electrochemical kinetics with LBM computational fluid dynamics (CFD) as shown in Figure 2. This kinetic model simulates the chemical reaction in the cathode side in order to investigate the electrical potentials, electrical current, electron transfer, and exchange current in the catalyst layers. It shows the potential capability of a CFD-based investigation of multi-physical transport to find solutions of design and operational conditions in the PEFC. 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. Moreover, the predictions from CFD simulations can help to optimize the design of porous layer structures and other components, such as flow fields, thereby improving the PEFC’s overall performance, cost of production, and development time. References: 1. U. Frisch, B. Hasslacher, Y. Pomeau, Physical review letters, 56 (14), (1986) 1505-1508. 2. R. McNamara, G. Zanetti, Physical Review Letters, 61, (1988) 2332-2335. 3. 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. 4. 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. Figure 1