Nanoscale Oxygen Bubble Dynamics and Coupled Transport at Anode Catalyst Layer Particle Surfaces in PEM Water Electrolysis

Abstract The production of green hydrogen via proton exchange membrane water electrolysis (PEMWE) is significantly constrained by mass transport limitations at the anode, where oxygen bubble evolution obstructs catalyst sites and compromises performance at high current densities. Conventional models fail to capture the nanoscale interplay between bubble dynamics and local electrochemical reactions, thereby obscuring critical design principles for nanostructural optimization. To address this, we developed a nanoscale multiphysics framework using the Lattice Boltzmann Method to directly couple bubble dynamics with electrochemistry. We investigated how key structural parameters–including IrO2 particle and TiC support radii, IrO2 volume fraction, and ionomer thickness–govern system behavior in a representative nanoscale domain. Our simulations identified two decisive factors within this single-particle-scale framework. First, increasing the TiC support radius to 11 nm improves local mass transport and gives the highest simulated current response among the tested cases, despite a reduction in effective active-site density. Second, ionomer thickness controls stability over the simulated time window: thin layers (3 nm) lead to rapid performance degradation through vigorous bubble growth and pore blockage, whereas thicker coatings (5 nm) suppress bubble nucleation through reactant starvation. These results provide nanoscale mechanistic guidance for catalyst-layer design, but they should be upscaled to representative elementary volumes before being interpreted as electrode-level design rules.