Molecular dynamics study on the impacts of cations in sea salt aerosol on transport performance of Nafion Membranes for PEMFCs in marine application

The application of polymer electrolyte membrane fuel cells (PEMFCs) in marine industry receives a widespread attention, due to the severe emission regulations. However, cationic contaminants in sea salt aerosol have detrimental effects on the transport performance of polymer electrolyte membranes, which are the core components of PEMFCs. In this study, the effects of K+ and Mg2+ in marine atmosphere on the transport performance of Nafion 117 membranes were evaluated by molecular dynamics simulations. Moreover, the influence of temperature is considered for the first time. The mean square displacements are used to evaluate the diffusion coefficients of water molecules (H2O) and hydronium ions (H3O+). In addition, the effect mechanisms are analyzed using radial distribution functions, water clusters distribution and relative concentration distribution. Results show that the diffusion of H3O+ and H2O is significantly weakened by K+ and Mg2+. Moreover, the impact of Mg2+ is more serious. The difference in the influence of these two kinds of cations on the transport performance of Nafion membranes is discussed by hydrated radius, hydration degree of cations, and the interaction between cations and sulfonic groups. The diffusion coefficients increase significantly with the increase of temperature. The increase of the temperature can also increase the interaction between the cations and the sulfonic groups. In contrast, the interaction between the sulfonic groups and water molecules is decreased. (C) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

This study evaluated the effects of K+ and Mg2+ in marine atmosphere on the transport performance of Nafion 117 membranes through molecular dynamics simulations. It was found that these cations significantly weaken the diffusion of H3O+ and H2O, with Mg2+ having a more serious impact. The diffusion coefficients increase significantly with the increase of temperature, along with the increase of interaction between cations and sulfonic groups.