Surface X-ray diffraction has been employed to
quantitatively determine the geometric structure of an X-ray-induced
superhydrophilic rutile-TiO2(110)(1 × 1) surface. A scatterer, assumed
to be oxygen, is found at a distance of 1.90 ± 0.02 Å above the five-foldcoordinated surface Ti atom, indicating surface hydroxylation. Two
more oxygen atoms, situated further from the substrate, are also included
to achieve the optimal agreement between experimental and simulated
diffraction data. It is concluded that these latter scatterers are from water
molecules, surface-localized through hydrogen bonding. Comparing this
interfacial structure with previous studies suggests that the superhydophilicity of titania is most likely to be a result of the depletion of surface carbon contamination coupled to extensive surface
hydroxylation