Photoemission study on the adsorption of ethanol on clean and oxidized rutile TiO2(110)-1 × 1 surfaces

Synchrotron radiation photoemission spectroscopy is employed to study the adsorption of ethanol on the rutile TiO2(110) surface at room temperature (RT). For the present study, well-characterized clean and oxidized rutile TiO2(110) surfaces are reproduced and ethanol is subsequently dosed at RT. We observe that the band-gap state varies in intensity upon ethanol adsorption on TiO2(110) at RT. Especially, the band-gap state is enhanced in intensity when ethanol is dosed on the oxidized TiO2(110) surface. These observations imply that the adsorption of ethanol induces a change in the surface charge associated with defects such as oxygen vacancies and Ti3+ interstitials due to an attractive interaction between ethanol and such defects. Interestingly, pre-dosed ethanol on TiO2(110) is observed to inhibit the attenuation of the band-gap state during subsequent O2 dose at RT. We interpret the result from a site-blocking effect by the pre-adsorbed ethanol both on oxygen vacancies and Ti4+ sites in inhibiting the interaction between O2 and surface defects on the TiO2(110) surface.