Determination of Transport Properties of Gas Diffusion Layer for PEMFC with GeoDict

The transport properties of gas diffusion layers (GDL) are crucial for the performance of proton-exchange membrane fuel cells (PEMFC). However, it is challenging to experimentally measure gas permeability and diffusion coefficients. GeoDict allows us to estimate the transport properties of GDLs by using 3D structures obtained from X-ray tomography scans. FlowDict module is used to determine gas permeability, while DiffuDict is employed to estimate diffusion coefficients.

The SatuDict module simulates the intrusion of water into the GDL's fibrous structure, providing insight into how water penetrates the hydrophobic material. This is critical since, at high current densities, flooding of the GDL is a major cause of performance loss. Visualizations show that when a GDL with a microporous layer (MPL) is used, water first infiltrates through the cracks. However, the inclusion of an MPL decreases the maximum saturation level in the fiber substrate, leading to improved performance compared to a GDL without an MPL. It is also found that the larger the cracks, the greater the transport properties. SatuDict gives access to the material's pressure-saturation curve.

By combining FlowDict and SatuDict, we determine the material's relative permeability, and by combining DiffuDict and SatuDict, we measure its relative diffusion coefficient. A mercury intrusion simulation is performed to provide a non-destructive method for measuring the pore size distribution. The addition of PTFE reduces gas permeability and diffusion coefficients, resulting in a loss of performance.