Local hydroxyl adsorption geometry on TiO${}_2$(110)

The local structure of the hydroxyl species on the rutile TiO${}_2$(110) surface has been determined both experimentally and computationally. The experimental study exploited chemical state–specific O 1s scanned-energy mode photoelectron diffraction from a surface exposed to atomic hydrogen, while density functional theory calculations were used to provide complementary information. As expected on the basis of previous studies, the bridging O atoms of the clean surface are hydroxylated, but this causes surprisingly small changes in the surrounding surface relaxation. Experiment and theory are in good agreement regarding the magnitude of these atomic movements. Specifically, the Ti-O${}_{\mathrm{OH}}$ surface bond is significantly longer (by 0.10–0.15 Å) than that of Ti-O${}_{\mathrm{bridging}}$ bonds on the clean surface.

Figure 1

Schematic model of the clean TiO${}_2$(110) surface with the Ti and O atoms of the different layers labeled following the convention of Ref. 1. These labels are used in identifying the displacements listed in Table .

Figure 2

O 1s photoemission spectra recorded before and after H dosing, showing the two component (OH and oxidic) peaks.

Figure 3

Comparison of the experimental PhD modulation spectra with the results of simulations for (a) the “simple” bridging-site model and (b) the “zigzag” OH row model, both on a bulk-terminated substrate. The O atoms of the OH species in the outermost layer are shown in a paler color. No H atoms are shown.

Figure 4

Comparison of the experimental PhD modulation spectra with the results of simulations for the relaxed bridging-site model based on reoptimization of the structural parameter values obtained in the DFT minimum-energy structure. The O atoms of the OH species in the outermost layer are shown in a paler color. No H atoms are shown.