Reaction Kinetics of Water Molecules with Oxygen Vacancies on Rutile TiO2(110)

Abstract

The formation of bridging hydroxyls (OHb) via reactions of water molecules with oxygen vacancies (VO) on reduced TiO2(110) surfaces is studied using polarized infrared reflection–absorption spectroscopy (IRAS), electron-stimulated desorption (ESD), and photon-stimulated desorption (PSD). Narrow IR peaks at 2737 and 3711 cm−1 are observed for the stretching vibrations of ODb and OHb, respectively. The IRAS spectra indicate that the bridging hydroxyls are oriented normal to the TiO2(110) surface. Using IRAS, we have studied the kinetics of water reacting with the vacancies by monitoring the formation of bridging hydroxyls as a function of the annealing temperature on the TiO2(110). Separate experiments have also monitored the loss of water molecules (using water ESD) and vacancies (using the CO photooxidation reaction) due to the reactions of water molecules with the vacancies. All three techniques show that the reaction rate becomes appreciable for T > 150 K and that the reactions are largely complete for ...