Surface Structure of TiO₂ Rutile (011) Exposed to Liquid Water

Abstract

The rutile TiO2(011) surface exhibits a (2 × 1) reconstruction when prepared by standard techniques in ultrahigh vacuum (UHV). Here we report that a restructuring occurs upon exposing the surface to liquid water at room temperature. The experiment was performed in a dedicated UHV system, equipped for direct and clean transfer of samples between UHV and liquid environment. After exposure to liquid water, an overlayer with a (2 × 1) symmetry was observed containing two dissociated water molecules per unit cell. The two OH groups yield an apparent “c(2 × 1)” symmetry in scanning tunneling microscopy (STM) images. On the basis of STM analysis and density functional theory (DFT) calculations, this overlayer is attributed to dissociated water on top of the unreconstructed (1 × 1) surface. Investigation of possible adsorption structures and analysis of the domain boundaries in this structure provide strong evidence that the original (2 × 1) reconstruction is lifted. Unlike the (2 × 1) reconstruction, the (1 × 1) surface has an appropriate density and symmetry of adsorption sites. The possibility of contaminant-induced restructuring was excluded based on X-ray photoelectron spectroscopy (XPS) and low-energy He+ ion scattering (LEIS) measurements.

Fluorine-programmed nanozipping to tailored nanographenes on rutile TiO 2 surfaces

“…Desorption of TiOF 2 points to strong Ti-F covalent bonding of F to the surface during the HF zipping, which may indirectly explain the observed surface reconstruction under newly formed HBC molecules. Adsorbates strongly interacting with the surface are known to induce changes in rutile titania reconstructions, as previously reported for (110) (39) and (011) (40,41) faces. Recent work by Balajka et al (41) reported a water-induced reconstruction of a rutile (011) surface to form a bulk-terminated (1×1) face covered with a hydroxyl group overlayer forming (2×1) reconstruction.…”

Bulk-terminated or reconstructed Fe3O4(001) surface: water makes a difference

“…Besides the influence on physical and chemical properties, an overlayer of water was recently proved to change the reconstruction of the technologically relevant TiO 2 rutile (011) surface. 1 Therefore, the adsorption mechanism of water on metal oxide surfaces is a key aspect to be investigated in order to control and improve processes that take place at the solid/liquid interface.…”

Curved TiO2 Nanoparticles in Water: Short (Chemical) and Long (Physical) Range Interfacial Effects

“…Additionally, water mono or multilayer adsorption may alter the surface electronic properties and work function, as well as the surface energy leading to different reconstructions than in ultra-high vacuum conditions. 3 Recently, it was even reported to affect the trapping dynamics of photogenerated charge carriers in TiO 2 . 4 , 5 …”