Water adsorption on r‐TiO₂(110): Presence of a well‐defined (1 × 1)‐structure as evidenced by He‐atom scattering

Abstract

The adsorption of water on r‐TiO2(110) has been investigated with thermal desorption spectroscopy (TDS) and helium atom scattering. Conventional TDS using a mass spectrometer and He‐TDS monitoring reflected He beam intensity consistently show the existence of a structurally well‐defined monolayer as well as a highly ordered second layer of water and a disordered multilayer phase. He diffraction patterns recorded along the high symmetry [001], $[1{\bar {1}}0]$, and $[1{\bar {1}}1]$ directions reveal a well‐ordered superstructure with (1 × 1) symmetry, providing strong evidence for the absence of a partially dissociated monolayer on the perfect parts of the substrate. No changes in the diffraction patterns are observed after irradiation with UV‐light.

Adsorbate-induced lifting of substrate relaxation is a general mechanism governing titania surface chemistry

“… 7 ). Both, the presence of a (1 × 1) structure and a binding energy of 0.82 eV for water on rutile TiO 2 (110) have been confirmed by recent experiments 26 .…”

“…The present set-up was recently used to determine a (1 × 1) adsorption geometry for water adsorbed on rutile TiO 2 (110) (ref. 26 ). The probing beam has kinetic energies between E i =10 and 80 meV and consists of neutral He atoms to avoid beam damage.…”

Probing electrons in TiO2 polaronic trap states by IR-absorption: Evidence for the existence of hydrogenic states

“…To remove contaminations present on the surface of the powder particles, the supporting metal grid was heated to 700 K for 60 min under UHV conditions, as used in previous works112023. For the single crystal experiments a r-TiO 2 (110) specimen (MATECK GmbH, Jülich, Germany) with a size of 10 × 10 mm 2 was cleaned using previously published preparation procedures131 including Ar + ion sputtering and annealing steps until the sample was a clean (as judged from XPS data), well-ordered (as judged from the presence of well-defined spots in the LEED-pattern) and largely defect-free (as judged from the comparison of UPS-data with those reported in32). Exposure to H atoms was carried out by operating a hot tungsten filament in line of sight of the titania samples in an atmosphere of 1 × 10 −6 –5 × 10 −7  mbar of H 2 , as described previously33.…”

Conversion of Alcohols on Stoichiometric and Reduced Rutile TiO2 (110): Point Defects Meet Bifunctionality in Oxide (Photo-)Chemistry

“…If water and alcohols are both present at the surface, this implies, that the rate-limiting steps are expected to be located at the alcohol if the coverage is low enough to avoid site blocking and intermolecular effects. However, at least for stoichiometric, defect-free surfaces, there is no consensus if water dissociates upon adsorption or not, or if mixed phases are dominating the surface [94,[97][98][99]. Accordingly, dissociated and molecular water are similar in energy and the activation barriers for dissociation and recombination are very low [72,93,99].…”