Wet electrons at the H2O/TiO2(110) surface

Area of Science:

• Surface Science
• Photochemistry
• Materials Science

Background:

• Electron transfer at metal oxide-water interfaces is fundamental to many chemical and physical processes.
• Partially hydrated or "wet-electron" states are proposed as key intermediates in these electron transfer pathways.

Purpose of the Study:

• To investigate the photoinduced electron transfer dynamics at the H2O/TiO2(110) interface.
• To characterize the nature and energetic position of transient electronic states formed upon photoexcitation.

Main Methods:

• Time-resolved two-photon photoemission spectroscopy was employed to probe electronic states.
• Density functional theory (DFT) calculations were used to elucidate electronic structure and bonding.

Main Results:

• An unoccupied electronic state, 2.4 eV above the Fermi level, was observed at ~1 monolayer water coverage on TiO2(110).
• DFT confirmed this state as a "wet-electron" state, distinct from hydrated electrons on metal surfaces.
• Electrons in this wet-electron state transferred to the TiO2 conduction band in ≤15 femtoseconds.

Conclusions:

• The "wet-electron" state represents a low-energy pathway for interfacial electron transfer at the H2O/TiO2 interface.
• The rapid electron transfer dynamics are critical for understanding photocatalysis and interfacial charge separation.