Photoinduced Dynamics at the Water/TiO_{2}(101) Interface

Area of Science:

• Surface Science
• Photocatalysis
• Materials Chemistry

Background:

• Understanding interfacial charge transfer is key to optimizing photocatalytic efficiency in systems like water splitting.
• Anatase titanium dioxide (TiO₂) is a widely studied semiconductor photocatalyst, but its interfacial dynamics with water require further elucidation.

Purpose of the Study:

• To investigate the ultrafast dynamics of charge transfer at the water/anatase TiO₂(101) interface.
• To determine the mechanism and timescale of hole transfer from TiO₂ to adsorbed water molecules.

Main Methods:

• Femtosecond time-resolved optical pump-soft X-ray probe photoemission spectroscopy.
• Ehrenfest molecular dynamics simulations.
• Analysis of transient oxygen O 1s core level peak shifts.

Main Results:

• Ultrafast interfacial hole transfer from TiO₂ to molecularly adsorbed water occurs within 285 fs.
• Hydrogen bond formation between surface oxygen (O₂c) and physisorbed water facilitates hole transfer.
• Dissociative adsorption of water forms hydroxyl species (-OH) that trap holes, preceding transfer.
• Interfacial charge transfer is suppressed at water coverages exceeding a monolayer.

Conclusions:

• The study reveals a femtosecond mechanism for interfacial hole transfer at the water/TiO₂ interface.
• Hydrogen bonding and hydroxyl intermediates play critical roles in mediating charge transfer dynamics.
• Findings provide fundamental insights into water-based photocatalysis and energy conversion.