Metal–Water Interface Formation: Thermodynamics from Ab-Initio Molecular Dynamics Simulations

03 July 2024, Version 2
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Metal–water interfaces are central to many electrochemical, (electro)catalytic, and materials science processes and systems. However, our current understanding of their thermodynamic properties is limited by the scarcity of accurate experimental and computational data and procedures. In this work, thermodynamic quantities for metal–water interface formation are computed for a range of FCC(111) surfaces (Pd, Pt, Au, Ag, Rh, and PdAu) through extensive density functional theory based molecular dynamics and the two-phase entropy model. We show that metal–water interface formation is thermodynamically favorable and that most metal surfaces studied in this work are completely wettable, i.e., have contact angles of zero. Interfacial water has higher entropy than bulk water due to the increased population of low-frequency translational modes. The entropic contributions also correlate with the orientational water density and the highest solvation entropies are observed for interfaces with a moderately ordered first water layer; the entropic contributions account for up to ca. 25 % of the formation free energy. Water adsorption energy correlates with the water orientation and structure, and is found to be a good descriptor of the internal energy part of the interface formation free energy but it alone cannot satisfactorily explain the interfacial thermodynamics; the interface formation is driven by the competition between energetic and entropic contributions. The obtained results and insight can be used to develop, parametrize, and benchmark theoretical and computational methods for studying metal–water interfaces. Overall, our study yields benchmark-quality data and fundamental insight into the thermodynamic forces driving metal–water inter- face formation.

Keywords

Electrochemistry
Solvation
Solid-Liquid Interfaces
Implicit solvent models
Thermodynamics

Supplementary materials

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Title
Supplementary material for Metal-Water Interface Formation: Thermodynamics from Ab-Initio Molecular Dynamics Simulations
Description
S1: Details on the free energy calculations, S2: Computation of interfacial entropies, S3: The bending and stretching mode DoS for interfacial and bulk water, S4: Electrostatic potential profiles, S5: Comparison of translational and rotational DOSs, S6: Convergence and uncertainty analysis, S7: Potentials of zero charge
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