This study presents a comprehensive numerical analysis of the characteristics of the gas diffusion layer (GDL) in proton exchange membrane fuel cells (PEMFCs). Fuel cells are devices that generate electricity by reacting hydrogen with oxygen. Hydrogen supplied from a high-pressure tank reacts with oxygen within the fuel cell stack, generating electricity that drives a motor. Given the diverse design requirements for fuel cells, including applications in commercial vehicles and stationary systems, efficient material design through numerical models and simulations is indispensable. The GDL, composed of carbon fibers and resin, functions as a cushion under cell compression and facilitates the transport of electrons, heat, gas, and water. Its microstructure significantly influences these properties, making precise design crucial.
In this study, we automated the material exploration by varying parameters such as the diameter and quantity of carbon fibers, as well as the amount and distribution of resin, to calculate gas diffusivity under humid conditions. The simulations considered structural changes due to compression, comparing load-displacement curves and pore size distributions before and after compression. While macroscopic modeling of compression behavior has been conducted, it does not account for the microscale behavior of CF and resin. Although some studies have simulated pore structures, FEM solid models only consider linear behavior, failing to reproduce behavior at low surface pressures and incurring high computational costs. In this study, we treated CF as beam elements and considered resin with spring characteristics at CF junctions, achieving high reproducibility of structural changes.
Using optimization algorithms, we identified the optimal design variables to enhance performance. Key functional properties calculated included permeability (in-plane and through-plane), electrical and thermal conductivity, deflection, spring characteristics under compression, and inhibition of liquid water transport. This study successfully identified designs that improve these properties and elucidated critical trade-offs between electrical conductivity and mass transport, as well as between mass transport and deformation. These findings provide valuable guidelines for the design and optimization of GDL materials, contributing to the advancement of PEMFC technology.