A stochastic multiphysics framework for elucidating nanoscale structure-mechanics-transport coupling in polymer electrolyte membranes

Abstract

Polymer electrolyte membranes govern fuel cell efficiency and durability; however, the coupled interplay among structure, deformation, and transport remains elusive at the nanoscale. Here, a stochastic multiphysics framework is developed by integrating nanoscale membrane morphology reconstruction, clamping-induced deformation, and multiple proton-transport mechanisms. A Nafion membrane is reconstructed using dissipative particle dynamics with a drying–rehydration protocol to capture phase separation and anisotropic swelling. A Winkler foundation model predicts non-uniform compression under realistic clamping, whereas proton transport is resolved into surface hopping, vehicular diffusion, and Grotthuss diffusion. The multiphysics model is quantitatively validated against experimental data. Increasing hydration enhances water-domain percolation and reduces tortuosity, thereby shifting transport dominance toward the Grotthuss mechanism while softening the membrane and amplifying deformation. Consistent with experimental trends, proton conductivity increases by nearly three orders of magnitude, from 2.0 × 10−4 to 6.0 × 10−2 S cm−1, as the water content increases from λ = 2 to 14, owing to hydration-induced water-domain percolation, reduced tortuosity, and enhanced Grotthuss transport. A lower equivalent weight improves domain connectivity and proton conductivity but intensifies localized strain. Pore-filling reinforced architectures mitigate deformation while preserving through-plane transport alignment, achieving a proton conductance of 31.2 S cm−2 compared with 3.36 S cm−2 for a normal membrane. This framework elucidates intrinsic trade-offs among nanoscale morphology, mechanical response, and proton transport, providing computation-driven design guidelines beyond current experimental accessibility.