Multiscale Modeling of Proton Conduction in Nafion Membranes—Integrating Coarse-Grained Molecular Dynamics and Continuum Calculations

Proton exchange membrane fuel cells (PEMFCs) depend on the effective transfer of protons across Nafion membranes to attain optimal performance and durability. It is of great importance to gain an understanding of the complex relationship between the structure of the membrane, external factors such as temperature and humidity, and the mechanisms of proton conduction if these fuel cells are to be optimised. In this study, we developed a multiscale modelling framework that integrates coarse-grained molecular dynamics (CGMD) with continuum-level calculations, with the objective of elucidating the proton conduction mechanisms in Nafion membranes. The model captures both the Grotthuss and vehicle mechanisms of proton transport, thereby enabling an investigation of their dependence on varying hydration levels and temperature conditions.

This work addresses the shortcomings of existing single-scale models by providing a comprehensive simulation that bridges the gap between molecular-level phenomena and macroscale behaviours. The structural properties of the Nafion membrane, including porosity and tortuosity, were analysed under different operational conditions, and the simulation results were validated against experimental data. Our findings demonstrate that while both conduction mechanisms contribute to proton transport, their relative significance varies with environmental factors, particularly hydration levels. Moreover, we investigate the possibility of optimising membrane design to enhance proton conductivity, reduce degradation and improve overall fuel cell efficiency.

The integration of CGMD with finite difference methods (FDM) to model proton conduction in Nafion membranes represents a significant contribution to both the academic understanding and practical applications of PEMFC technologies. Our study offers a novel approach to optimising proton exchange membranes, providing insights that can guide the development of next-generation materials for energy applications. These findings are expected to have broad implications for enhancing the efficiency and sustainability of fuel cells in a variety of industries, including transportation and renewable energy storage.