Abstract
The performance of proton-exchange membrane fuel cells (PEMFCs) is constrained by coupled transport and reaction processes within the catalyst layer (CL). In this study, oxygen mass transfer in reconstructed porous CL structures was analyzed using the lattice Boltzmann method (LBM) and the quartet structure generation set (QSGS). A three-dimensional microstructure was reconstructed by prescribing phase fractions and growth probabilities. Pt agglomeration, carbon-support corrosion, and ionomer degradation were represented to analyze morphological evolution and its influence on transport. The results reveal that integrated degradation triggers a complex, non-monotonic evolution of mass transfer resistance ( R cl ). In the early stages, the thinning of the ionomer film and initial structural reconfiguration shorten the gas diffusion pathways, leading to a transient reduction in R cl . However, as degradation intensifies, the massive loss of electrochemical active surface area (ECSA), the structural collapse of the carbon skeleton, and the diminished proton conductivity of the ionomer phase collectively lead to a non-linear spike in R cl . The resulting structure-transport mapping provides a pore-scale basis for durability-oriented catalyst layer design.