Prof. Mischa Bonn "Molecular Mechanics of Aqueous Interfaces: from Ångström Confinement to Electric Double Layers"

Abstract

Understanding how water, ions, and surfaces interact across length scales is central to electrochemistry, nanofluidics, and catalysis. Across three studies, we established a molecular view of structure and dynamics at aqueous interfaces under confinement and electrostatic perturbation.  We have demonstrated that, down to the angstrom-scale confinement, interfacial effects entirely determine the organization of confined water, disrupting bulk-like hydrogen bonding and producing asymmetric environments due to wall contact [1]. These findings establish that nanofluidic behavior is governed not by the confined volume, but by its bounding interfaces. We extended this picture to show that even nominally neutral materials, such as hexagonal boron nitride, acquire a spontaneous surface charge at the aqueous interface [2]. This intrinsic charging, observed in other solids as well, indicates that the formation of an electric double layer (EDL) is nearly universal at solid–liquid boundaries. Finally, we resolved the ultrafast dynamics of the aqueous EDL using femtosecond-resolved optical spectroscopy, showing that ionic rearrangements occur within tens of picoseconds — faster than diffusion-limited models predict [3]. Together, these studies provide a molecularly consistent understanding of how interfacial polarization, confinement, and charge collectively define water’s behavior in nanofluidic and electrochemical environments.

[1] Nat. Commun. 16, 7288 (2025)

[2] J. Am. Chem. Soc. 147, 30107 (2025)

[3] Science 388, 405 (2025)

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Organizer  Giulio RAGAZZON