Acetone-Assisted Oxygen Vacancy Diffusion on TiO2(110).

Abstract

We have studied the dynamic relationship between acetone and bridge-bonded oxygen (Ob) vacancy (VO) defect sites on the TiO2(110)-1 × 1 surface using scanning tunneling microscopy (STM) and density function theory (DFT) calculations. We report an adsorbate-assisted VO diffusion mechanism. The STM images taken at 300 K show that acetone preferably adsorbs on the VO site and is mobile. The sequential isothermal STM images directly show that the mobile acetone effectively migrates the position of VO by a combination of two acetone diffusion channels: one is the diffusion along the Ob row and moving as an alkyl group, which heals the initial VO; another is the diffusion from the Ob row to the five-coordinated Ti(4+) row and then moving along the Ti(4+) row as an acetone, which leaves a VO behind. The calculated acetone diffusion barriers for the two channels are comparable and agree with experimental results.