Role of Coverage and Surface Oxidation Degree in the Adsorption of Acetone on TiO2 (110). A Density Functional Study

A systematic study of the adsorption of acetone on a TiO2 (110) surface by means of plane-wave pseudopotential density-functional theory calculations is presented. The relationship between the binding energy of acetone and the degree of surface coverage (up to 0.5 ML) is established on the basis of a partial reduction of the surface by the incoming acetone molecules. This allows one to explain the observed displacement toward lower temperature of the temperature-programmed desorption (TPD) maximum with increasing acetone loading. Adsorption at the bridge oxygen vacancies on supercell models of the reduced surface shows similar properties to that of regular Ti channel sites, in agreement with experimental data that do not indicate a preferential binding at vacancy sites. A high dependency between the degree of reduction of the surface and the acetone binding energies is found, implying that surface models with an excessive mean number of vacancies per unit cell may result in altered properties of this surf...