Cation-Dependent Ion Dynamics and Morphology in Metal-Contaminated Nafion Membranes
Year: 2026
Type: preprint
Abstract: Metal cation contamination of Nafion proton-exchange membranes (PEMs) remains a persistent durability and performance issue in water electrolyzers as well as fuel cells. Contaminant metal cations originating from insufficiently deionized feed water, coolant leaks, or corrosion of metal cell components can bind to the sulfonate groups of Nafion, thereby interfering critically with proton transport. This work is the first joint experimental-simulation study that systematically elucidates the atomistic processes behind the metal-cation-based inhibition of proton conductivity in Nafion. The impact of humidity, metal cation charge, and temperature on morphology and ion transport is studied. Combining in-plane conductivity measurements of various metal cation impurities with classical molecular dynamics (MD) simulations reveals different water uptake at constant relative humidity (RH) driven by the chemical potential. The ion dynamics decrease from Li+ to K+ at constant RH, which is the exact opposite to the trend observed in bulk water. The apparent contradiction is identified as a consequence of the cation-water interaction dominating the water uptake and consequently the extent of percolation pathways. In contrast, the cation-sulfonate interaction is the decisive factor describing how the charge of metal cations impact conductivity in Nafion. By multidentate interaction of multivalent metal cations with multiple sulfonate groups, the pore is locally constricted disconnecting percolation pathways and inhibiting ion transport.
Source: ChemRxiv
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7211903723