Spatial Engineering of Gas Diffusion Layers Overcomes Mass Transport Limitations in Fuel Cells

Mass transport limitations at high current densities hinder polymer electrolyte fuel cell (PEFC) performance due to inefficient water management and reactant distribution. Gas diffusion layer (GDL) perforation offers a potential solution as an alternative to complex flow-field modifications. However, understanding of how perforation impacts critical internal states like water distribution, local temperature and electrochemical reaction rates remains limited. This knowledge gap has prevented optimisation of GDL designs, with homogeneous patterns  potentially exacerbating performance gradients. This study uses operando neutron imaging combined with synchronous thermal-electrical mapping to analyse water dynamics and their impact on PEFC performance with both homogeneous and heterogeneous GDLs. The approach enables detailed analysis of interactions between water, heat and electrochemical reactions, providing experimental validation beyond limited field-of-view techniques like X-ray tomography. Results demonstrate that a spatially tailored perforation pattern effectively balances in-plane saturation gradients and enhances peak power compared to both uniform patterns and non-perforated GDLs. This work establishes spatial engineering as a design principle for porous transport layers, offering a simpler and cost-effective solution to mass transport constraints in fuel cells and other electrochemical devices containing porous media.