Elucidating the water-anatase TiO2(101) interface structure using infrared signatures and molecular dynamics

Area of Science:

• Surface science
• Materials chemistry
• Physical chemistry

Background:

• Water structure on solid surfaces impacts material chemistry.
• Anatase titanium dioxide (TiO2) is a key photocatalyst.
• Understanding the water-anatase (101) interface is essential.

Purpose of the Study:

• To investigate the hydrogen bonding network of water on the anatase TiO2 (101) surface.
• To elucidate the structural changes of water adsorption with increasing coverage.
• To provide experimental confirmation of hypothesized interfacial structures.

Main Methods:

• Polarization- and azimuth-resolved infrared spectroscopy.
• Neural network potential molecular dynamics simulations.
• Combined spectroscopic and computational approach.

Main Results:

• One monolayer of water saturates undercoordinated titanium (Ti5c) sites, forming 1D chains bonded to bridging oxygen (O2c) atoms.
• Increased water coverage restructures the monolayer, forming a 2D network with water pairs on adjacent Ti5c and O2c sites.
• This 2D network structure is likely stable under ambient conditions.

Conclusions:

• The study reveals detailed structural motifs of water on the anatase (101) surface.
• The findings confirm previously hypothesized interfacial structures experimentally.
• The characterized water structure influences surface chemistry and reactions at ambient conditions.