The influence of point defects (oxygen vacancies) and steps on the reactivity of TiO2(100) was studied with low-energy electron diffraction and soft X-ray photo-emission using H2O as a model adsorbate. An O termination of the TiO2(100)-(1 x 1) surface was deduced by comparison of surface core-level shift data for this surface and TiO2(001); ordering of O vacancies produced in the surface layer by annealing gives rise to a TiO2(100)-(1 x 5) reconstruction. The interaction of H2O with 1 x 1 and 1 x 5 TiO2(100) surfaces in the range 120 to 450K was almost identical, indicating that the ordered oxygen vacancies of the 1 x 5 surface did not play a major role in the surface chemistry. A comparison of planar and 3 degrees vicinal TiO2(100)-(1 x 1) reactivity showed that steps also play a spectator role. Although unreactive at room temperature, H2O adsorbs molecularly at 120K. Thermally induced dissociation occurred on annealing, to form Ti-O-H species with a bond angle of approximately 90 degrees.

TiO2(100) Structure-Reactivity Relationship. Muryn, C.A., Tirvengadum, G., Crouch, J.J., Warburton, D.R., Raiker, G.N., Thornton, G., Law, D.S.L.: Journal of Physics - Condensed Matter, 1989, 1[SB], 127-32