Pore-Scale Investigation of Oxygen Transport in Proton Exchange Membrane Fuel Cell Catalyst Layers with Carbon Supports of Diverse Morphologies

The morphology of carbon supports critically governs oxygen transport and electrochemical performance in proton exchange membrane fuel cell (PEMFC) cathode catalyst layers. Here, we develop a pore-scale modeling framework coupling stochastic three-dimensional reconstruction and a lattice Boltzmann diffusion-reaction model to resolve local oxygen concentration, reaction rate, electrochemically active surface area, and current density. Optimized ellipsoidal supports with a semiaxis of 60 nm enhance pore connectivity and oxygen utilization, increasing peak current density by 18% compared with the spherical baseline and raising ionomer-phase oxygen concentration by 25%. Bowl-shaped supports with Rinner = 31 nm also improve performance, achieving a current density of 429.1 mA/cm2 and an oxygen concentration 12% higher than the baseline, whereas plate-shaped supports induce severe oxygen depletion near the membrane, reducing current density to 189.2 mA/cm2. CNT supports improve transport pathways but yield limited gains, with oxygen concentration increasing by 8% due to constrained active site utilization. These quantitative results establish clear morphology-structure-performance relationships, providing theoretical guidance for the design of high-performance, low-Pt PEMFC cathode catalyst layers.