Electric field assisted migration of H+ and Cu+/Cu++ ions through the Nafion in Cu-Cl electrolyzer for hydrogen Generation: Molecular dynamics simulations

P Sahu and SM Ali, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 994, 119267 (2025).

DOI: 10.1016/j.jelechem.2025.119267

This study explores the transport of proton and copper ions in hydrated Nafion membranes within a Cu-Cl electrolyzer, a key component of hybrid Cu-Cl cycle for hydrogen production. Particular focus is given to the effects of membrane hydration level and applied electric field strength. Molecular dynamics (MD) simulations reveal that electric fields enhance proton mobility by promoting water structuring and aligning hydronium ion trajectories, leading to a transition from diffusive to drift- dominated transport. Conversely, copper ions-especially Cu2+-disrupt the hydrogen-bonding network through solvation shell formation, thereby significantly diminish the ionic conductivity. While both hydration and field strength improve transport, hydration exerts a stronger influence. Conductivity increases with both factors but saturates at high field strengths, suggesting a threshold beyond which water drag impedes ion mobility. The presence of acidic medium was found to boost conductivity, whereas copper ions were seen to suppress it-markedly by Cu2+. These insights reveal the microscopic mechanisms of hydronium transport and copper-induced nafion degradation, offering guidance for the design of advanced ionomer membranes in electrolyzer and energy conversion applications.

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