Water Dissociates at the Aqueous Interface with Reduced Anatase TiO₂ (101)

Area of Science:

• Materials Science
• Surface Chemistry
• Catalysis

Background:

• Understanding the anatase titanium dioxide (TiO2) (101) water interface is key for photoassisted water splitting.
• The surface chemistry of TiO2 in vacuum differs significantly from its behavior in the presence of water.

Purpose of the Study:

• To elucidate the atomic structure of the room temperature interface between reduced anatase TiO2 (101) and both ultrathin and bulk water.
• To investigate the surface reactivity and bonding configurations at the TiO2-water interface.

Main Methods:

• Surface X-ray diffraction (SXRD) was employed to study the interface structure.
• Density functional theory (DFT) calculations were used to interpret the experimental SXRD results.

Main Results:

• The TiO2 (101) surface is not inert in the presence of water, featuring a mixture of molecular H2O and terminal/bridging OH species bound to titanium atoms.
• Both ultrathin and bulk water interfaces exhibit this reactive structure, contrasting with inertness observed in ultrahigh vacuum.
• In bulk water, the second water layer also shows ordering, with molecules hydrogen-bonded to the contact layer, influencing bond angles.

Conclusions:

• The reduced anatase TiO2 (101) surface is chemically active when in contact with water, forming specific molecular and hydroxyl configurations.
• The findings provide critical insights into the initial steps of water interaction with TiO2, essential for photocatalysis and water splitting applications.
• Structural differences between ultrathin and bulk water interfaces highlight the influence of water layering on surface properties.