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Proceedings Paper

Ultrafast proton-coupled electron transfer in heterogenous photocatalysis
Author(s): Jin Zhao; Ken Onda; Bin Li; Hrvoje Petek
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Paper Abstract

At metal-oxide/protic-solvent interfaces, partially hydrated or "wet electron" states represent the lowest energy pathway for electron transfer. Here we study the photoinduced charge transfer at the H2O/TiO2(110) interface by means of timeresolved two-photon photoemission spectroscopy and electronic structure theory. At ~1 monolayer coverage of H2O on partially hydroxylated TiO2 surfaces we find an unoccupied electronic state 2.4±0.1 eV above the Fermi level. Density functional theory shows this to be a two-dimensional "wet electron" state, which is distinct from hydrated electrons observed on water-covered metal surfaces. The decay of electrons from the wet electron state by the resonant charge transfer to the conduction band of TiO2 occurs in ≤15 femtoseconds. Similar unoccupied electronic structure is observed for CH3OH covered TiO2(110) surfaces; however, the electron dynamics are considerably more complex. The wet electron state dynamics of CH3OH/TiO2 exhibit both energy and population decay. The excited state lifetime is strongly coverage dependent increasing to >100 fs range above 1 ML CH3OH coverage. Significantly, a pronounced deuterium isotope effect (CH3OD) indicates a strong correlation between the interfacial electron transfer and the motion of protons in the molecular overlayer.

Paper Details

Date Published: 11 September 2006
PDF: 10 pages
Proc. SPIE 6325, Physical Chemistry of Interfaces and Nanomaterials V, 63250W (11 September 2006); doi: 10.1117/12.678279
Show Author Affiliations
Jin Zhao, Univ. of Pittsburgh (United States)
Ken Onda, Univ. of Pittsburgh (United States)
Bin Li, Univ. of Pittsburgh (United States)
Hrvoje Petek, Univ. of Pittsburgh (United States)

Published in SPIE Proceedings Vol. 6325:
Physical Chemistry of Interfaces and Nanomaterials V
Mark Spitler; Frank Willig, Editor(s)

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