First layer water phases on anatase TiO2(101)
Artikel i vetenskaplig tidskrift, 2018

The anatase TiO2(101) surface and its interaction with water is an important topic in oxide surface chemistry. Firstly, it benchmarks the properties of the majority facet of TiO2 nanoparticles and, secondly, there is a controversy as to whether the water molecule adsorbs intact or deprotonates. We have addressed the adsorption of water on anatase TiO2(101) by synchrotron radiation photoelectron spectroscopy. Three two-dimensional water structures are found during growth at different temperatures: at 100 K, a metastable structure forms with no hydrogen bonding between the water molecules. In accord with prior literature, we assign this phase to chains of disordered molecules. Growth 160 K results in a metastable structure with expressed hydrogen bonding between the water molecules. At 190 K, the water molecules become disordered as the thermal energy is too high and hence the hydrogen bonds break. The result is a structure with isolated monomers. Partial dissociation is observed for all three growths, with the molecular state only slightly favored in energy (20–40 meV) over the dissociated state. Heating of a thick film leads to more dissociation compared to a bilayer, when formed at 100 K. Thus, extending the water network facilitates proton transport and hence dissociation. The results reconcile apparent conflicting experimental results previously obtained by scanning tunneling microscopy (STM) and core level photoelectron spectroscopy.

Metal oxides

Anatase

TiO2

Dissociation

Water adsorption

Photoelectron spectroscopy

Monolayer

Författare

Andreas Schaefer

Lunds universitet

V. Lanzilotto

Uppsala universitet

U. Cappel

Kungliga Tekniska Högskolan (KTH)

Per Uvdal

Lunds universitet

Anne Borg

Norges teknisk-naturvitenskapelige universitet

Anders Sandell

Uppsala universitet

Surface Science

0039-6028 (ISSN)

Vol. 674 25-31

Ämneskategorier

Oorganisk kemi

Annan elektroteknik och elektronik

Den kondenserade materiens fysik

DOI

10.1016/j.susc.2018.03.019