Coverage-dependent two-photon photoexcitation at the H2O/TiO2 interface

• Published in: Surface science Vol. 652; pp. 189 - 194
• Main Authors: Payne, D.T., Zhang, Y., Pang, C.L., Fielding, H.H., Thornton, G.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2016
• Subjects: 2PPE; Hydroxyls; Photoexcitation; TiO2; Water; Water; Hydroxyls; 2PPE; Ob-vac; h-TiO2; OHb; r-TiO2; OHt; HB; BGS; TiO2; Photoexcitation
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2016.02.018

Excited electrons and holes are crucial for redox reactions on metal oxide surfaces. However, precise details of this charge transfer process are not known. We report two-photon photoemission (hν=3.23eV) measurements of rutile TiO2(110) as a function of exposure to water below room temperature. The two-photon resonance associated with bridging hydroxyls is enhanced following water exposure, reaching a maximum at a nominal coverage of one monolayer. Higher coverages attenuate the observed resonance. Ultraviolet photoemission spectroscopy (hν=21.22eV) of the initial, band gap states shows little change up to one monolayer water coverage. It is likely that the enhancement arises from dissociation within the adsorbed water monolayer, although other mechanisms cannot be excluded. [Display omitted] •Hydroxylated TiO2 shows water coverage-dependent two-photon photoexcitation.•The resonance signal reaches a maximum at a nominal water coverage of a monolayer.•This enhancement likely arises from a partial dissociation of the water monolayer.•Monolayer water does not alter the Ti 3d band gap states in photoemission data.