A molecular mechanism for the water-hydroxyl balance during wetting of TiO2

TL;DR

This study elucidates the molecular mechanism governing the water-hydroxyl balance during wetting of TiO2, combining experimental spectroscopy with theoretical modeling to explain the transition from hydroxyl to molecular water coverage.

Contribution

It reveals the formation and interactions of hydroxyl pairs and water molecules on TiO2(110), providing a detailed molecular-level understanding of wetting behavior.

Findings

Hydroxyl pairs form initially on TiO2 surface.

Repulsive interactions occur between hydroxyl pairs.

Transition to molecular water coverage occurs with increasing water.

Abstract

We show that the formation of the wetting layer and the experimentally observed continuous shift of the H2O-OH balance towards molecular water at increasing coverage on a TiO2(110) surface can be rationalized on a molecular level. The mechanism is based on the initial formation of stable hydroxyl pairs, a repulsive interaction between these pairs and an attractive interaction with respect to water molecules. The experimental data are obtained by synchrotron radiation photoelectron spectroscopy and interpreted with the aid of density functional theory calculations and Monte Carlo simulations.