Imaging reactions of acetone with oxygen adatoms on partially oxidized TiO2(110)

Abstract

Understanding the interaction of O₂ with ketones on metal oxide surfaces is important for the photo-oxidation of toxic organic molecules. The consecutive reaction steps of acetone molecules with oxygen adatoms (O_a's) on partially oxidized TiO₂(110) surfaces have been studied using high-resolution scanning tunneling microscopy (STM) at 300 K. The sequential isothermal STM images reveal two types of acetone–O_a species as a result of reactions of acetone with an oxygen adatom and a bridging bound oxygen vacancy (V_O). One such species is the Ti_5c-bound acetone–O_a diolate formed from Ti_5c-bound acetone reacting with O_a. The diolate is mobile at 300 K and can assist the diffusion of surface O_a by exchanging the acetone oxygen with the O_a. The second acetone–O_a species is the V_O-bound acetone–O_a complex formed from a V_O-bound acetone reacting with an O_a located on the neighboring Ti row. The V_O-bound complex is stationary at 300 K. This species has not been reported previously.