Substrate-Induced Cooperative Effects in Water Adsorption from Density Functional Calculations

TL;DR

This study uses density functional theory to explore how substrate effects influence water adsorption and hydrogen bonding on a Ru surface, revealing polarization effects and stability factors of water structures.

Contribution

It demonstrates substrate-induced polarization enhances hydrogen bonds in water dimers on Ru, providing insights into water structure stability on metallic surfaces.

Findings

Hydrogen-bond reinforcement is due to donor polarization.

Effect is consistent across different water cluster sizes.

Bonding of the acceptor molecule suppresses cooperative reinforcement.

Abstract

Density Functional Theory calculations are used to investigate the role of substrate-induced cooperative effects on the adsorption of water on a partially oxidized transition metal surface, O(2x2)/Ru(0001). Focussing particularly on the dimer configuration, we analyze the different contributions to its binding energy. A significant reinforcement of the intermolecular hydrogen-bond (H-bond), also supported by the observed frequency shifts of the vibration modes, is attributed to the polarization of the donor molecule when bonded to the Ru atoms in the substrate. This result is further confirmed by our calculations for a water dimer interacting with a small Ru cluster, which clearly show that the observed effect does not depend critically on fine structural details and/or the presence of co-adsorbates. Interestingly, the cooperative reinforcement of the H-bond is suppressed when the acceptor molecule, instead of the donor, is bonded to the surface. This simple observation can be used to rationalize the relative stability of different condensed structures of water on metallic substrates.