  A combination of Photoemission, Atomic Force and Scanning Tunneling
Microscopy/Spectroscopy measurements shows that excess electrons in TiO2
anatase (101) surface are trapped at step edges. Consequently, steps act as
preferred adsorption sites for O2. In Density Functional Theory calculations
electrons localize at clean step edges, this tendency is enhanced by O
vacancies and hydroxylation. The results show the importance of defects for the
wide-ranging applications of titania.
