Structure, Kinetics, and Thermodynamics of Water and Its Ions at the Interface with Monoclinic ZrO2Resolved via Ab Initio Molecular Dynamics

Funding Number

DE-AC05-00OR22725

Funding Sponsor

U.S. Department of Energy

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https://doi.org/10.1021/acs.jpcc.1c02064

Document Type

Research Article

Publication Title

Journal of Physical Chemistry C

Publication Date

7-22-2021

doi

10.1021/acs.jpcc.1c02064

Abstract

In this work, we assess the structural, kinetic, and thermodynamic nature of water in contact with the monoclinic ZrO2 (1¯ 11) surface by ab initio molecular dynamics calculations. We find that water molecules in the first layer immediately facing the solid surface have a preferred orientation, with one water intramolecular bond, Ow-Hw, lying parallel to the surface, and the other water hydrogen Hw atom pointing away from the surface. This originates from the electrostatic attraction between surface Zr and water's oxygen, Zr-Ow, and from the hydrogen bonding of surface oxygen and water's hydrogen, Os-Hw. The short-range interactions between interfacial water and the surface ions of ZrO2 lead to an ordered structure for water molecules, with alternating hydrogen-rich and oxygen-rich layers that persist for more than 5 Å away from the surface. The surface structural perturbation also leads to a shortened hydrogen-bond distance and distorted hydronium ion solvation shell, which leads to faster proton hopping dynamics and lowered solvation free energy of the hydronium ion. By analyzing these observations in a spatially resolved way, we demonstrate a clear link between the interfacial water structure, localized dynamics, and thermodynamic effects. This work provides an atomistic understanding of the interaction of hydrated protons with the ZrO2 surface in aqueous environment and allows for further engineering of oxide surfaces for targeted hydrogen activity.

First Page

15233

Last Page

15242

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