Adsorption of Acetone on Rutile TiO2: A DFT and FTIRS Study

Acetone adsorbed on rutile TiO2 nanoparticles was investigated with respect to its energetic, vibrational, and chemical properties. Temperature-dependent ultrahigh-vacuum Fourier transform infrared spectroscopy measurements for different acetone dosages (4.5–900 L) give insights into the acetone adsorption behavior. Those experiments indicate thermal-induced reactions of acetone on rutile TiO2 surfaces yielding new species. Density functional theory calculations were performed to investigate acetone adsorption on rutile TiO2(110). Particularly, the importance of sampling the adsorption configuration space is shown. Adsorption geometries that are energetically significantly more favorable than the commonly used high-symmetry configurations are presented. To facilitate the comparability to the experiment, theoretical infrared spectra were computed using density functional perturbation theory for various acetone adsorption geometries using different exchange-correlation functionals. Additionally, computational spectra were obtained for several species which are potential products from reactions of acetone on TiO2 surfaces. The investigated species are η2-acetate, η2-diolate, η1-enolate, and mesityl oxide. For η1-acetone, experimental and calculated spectra fit well for low temperatures, whereas for elevated temperatures, emerging bands indicate the formation of diolate.