arXiv subjects

Simone Pezzotti

Publications and source records attributed to Simone Pezzotti.

4 recordsLinked to original sources

arXiv2025

Resist the surface field: the H-bond network decides if water aligns at metal electrodes

At an electrode, water molecules align to the surface field upon voltage application. This initiates important electrochemical reactions, e.g., hydrogen and oxygen evolution reactions. Recently developed non-linear optical techniques challenge the traditional picture by quantifying a lack of water alignment at metal electrodes. We here provide theoretical and experimental evidences for the existence of a driving force that opposes water alignment to the surface field. Such driving force originates from the ordering templated by the metal surface on the physisorbed water layer, and scales with surface hydrophilicity. We hence propose a physical model for water alignment at electrodes based on a balance of H-bond network and surface field driving forces, which reconciles the traditional picture with the new experimental observations.

physics.chem-ph↗

arXiv2025

Surface charge pattern: impact on vibrational spectroscopy and physics of charged interfaces

Surface specific vibrational spectroscopies revolutionized the study of charged interfaces, by sensitively probing water's response in the electric double layer (EDL) and correlating it with surface charge via models like Gouy Chapmann Stern. The assumed one to one relationship between water's spectroscopic response and surface charge has been widely accepted without question. We hereby propose a theoretical experiment to evaluate this assumption. Interestingly, our findings reveal a non one to one relationship between surface charge and spectroscopic response, exhibiting a fascinating dependence on surface topology.

physics.chem-ph↗

arXiv2020

Size-dependence of hydrophobic hydration at electrified gold/water interfaces

Hydrophobic hydration at metal/water interfaces actively contributes to the energetics of electrochemical reactions, e.g. CO$_2$ and N$_2$ reduction, where small hydrophobic molecules are involved. In this work, constant applied potential molecular dynamics is employed to study hydrophobic hydration at a gold/water interface. We propose an extension of the Lum-Chandler-Weeks (LCW) theory to describe the free energy of hydrophobic hydration at the interface as a function of solute size and applied voltage. Based on this model we are able to predict the free energy cost of cavity formation at the interface directly from the free energy cost in the bulk plus an interface-dependent correction term. The interfacial water network contributes significantly to the free energy yielding a preference for outer-sphere adsorption at the gold surface for ideal hydrophobes. We predict an accumulation of small hydrophobic solutes of sizes comparable to CO or N$_2$, while the free energy cost to hydrate larger hydrophobes, above 2.5 Angstrom radius, is shown to be greater at the interface than in the bulk. Interestingly, the transition from the volume dominated to the surface dominated regimes predicted by the LCW theory in the bulk is also found to take place for hydrophobes at the Au/water interface, but occurs at smaller cavity radii. By applying the extended LCW theory to a simple model addition reaction, we illustrate some implications of our findings for electrochemical reactions.

physics.chem-ph↗

arXiv2020

An Isolated Water Droplet in the Aqueous Solution of a Supramolecular Tetrahedral Cage

Water under nanoconfinement at ambient conditions has exhibited low-dimensional ice formation and liquid-solid phase transitions, but with structural and dynamical signatures which map onto known regions of waters phase diagram. Using THz absorption spectroscopy and ab initio molecular dynamics, we have investigated the ambient water confined in a supramolecular tetrahedral assembly, and determined that a distinct network of 9-10 water molecules is present within the nanocavity of the host. The low-frequency absorption spectrum and theoretical analysis of the water in the $Ga_4$$L_6$$^{-12}$ host demonstrate that the structure and dynamics of the encapsulated droplet is distinct from any known phase of water. A further inference is that the release of the highly unusual encapsulated water droplet creates a strong thermodynamic driver for the high affinity binding of guests in aqueous solution for the $Ga_4$$L_6$$^{-12}$ supramolecular construct.

physics.chem-ph↗