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Science 20 May 2005:
Vol. 308. no. 5725, pp. 1154 - 1158
DOI: 10.1126/science.1109366
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Reports

Wet Electrons at the H2O/TiO2(110) Surface

Ken Onda,1 Bin Li,1 Jin Zhao,1 Kenneth D. Jordan,2 Jinlong Yang,3 Hrvoje Petek1*

At interfaces of metal oxide and water, partially hydrated or "wet-electron" states represent the lowest energy pathway for electron transfer. We studied the photoinduced electron transfer at the H2O/TiO2(110) interface by means of time-resolved two-photon photoemission spectroscopy and electronic structure theory. At ~1-monolayer coverage of water on partially hydroxylated TiO2 surfaces, we found an unoccupied electronic state 2.4 electron volts above the Fermi level. Density functional theory shows this to be a wet-electron state analogous to that reported in water clusters and which is distinct from hydrated electrons observed on water-covered metal surfaces. The decay of electrons from the wet-electron state to the conduction band of TiO2 occurs in ≤15 femtoseconds.

1 Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA.
2 Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260, USA.
3 Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026, China.

* To whom correspondence should be addressed. E-mail: petek{at}pitt.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)