Ab Initio Insight into Mechanisms of Ozone Interaction with a Surface of Dehydrated Nanocrystalline TiO₂

Density functional theory (DFT) study of ozone adsorption on dehydrated nanocrystalline TiO₂ is presented. Singlet and triplet binding modes of ozone to the oxide's titanium cations are considered. In both the modes, monodentate and bidentate ozone complexes are formed. According to DFT, the triplet monodentates are the most stable species. The formation of monodentate ozone adsorption complexes is in-line with an earlier interpretation of infrared (IR) spectroscopic data on ozone adsorption on an anatase surface. However, the computed difference in the fundamental vibrational frequencies (ν₁ - ν₃) of ozone in the triplet monodentates is significantly larger than the corresponding IR value. This discrepancy is resolved by demonstrating that the triplet monodentates readily decompose, realizing molecular oxygen that is consistent with published experimental data. The predicted energy barrier of the dissociative adsorption is less than 2 kcal/mol. In contrast, the computed difference in the fundamental vibrational frequencies (ν₁ - ν₃) of adsorbed ozone in the singlet bidentates perfectly agrees with the experiment.