Acetone-assisted oxygen vacancy diffusion on TiO ₂(110)

We have studied the dynamic relationship between acetone and bridge-bonded oxygen (O _b) vacancy (V _O) defect sites on the TiO ₂(110)-1 - 1 surface using scanning tunneling microscopy (STM) and density function theory (DFT) calculations. We report an adsorbate-assisted V _O diffusion mechanism. The STM images taken at 300 K show that acetone preferably adsorbs on the V _O site and is mobile. The sequential isothermal STM images directly show that the mobile acetone effectively migrates the position of V _O by a combination of two acetone diffusion channels: one is the diffusion along the O _b row and moving as an alkyl group, which heals the initial V _O; another is the diffusion from the O _b row to the five-coordinated Ti ⁴⁺ row and then moving along the Ti ⁴⁺ row as an acetone, which leaves a V _O behind. The calculated acetone diffusion barriers for the two channels are comparable and agree with experimental results.