Linear Correlations between Adsorption Energies and HOMO Levels for the Adsorption of Small Molecules on TiO2 Surfaces

Abstract

Adsorption is a fundamental step in catalysis on a solid surface, and therefore, its understanding is important for explaining its behavior. This work investigated the adsorption of various small molecules, including H2, N2, CO, CO2, CH4, NH3, H2O, H2S, dimethyl sulfoxide, alkanes, alkenes, alkynes, aromatic compounds, alcohols, aldehydes, ketones, nitriles, carboxylic acids, amides, and amines, on the anatase (101) and rutile (110) surfaces of TiO2, using periodic density functional theory calculations and statistical methods. Adsorption energies were computed at the same level of theory to obtain a clean and consistent data set. A linear relationship was observed between the adsorption energies of these molecules and their highest occupied molecular orbital (HOMO) levels, whereas no obvious correlation was evident for the lowest unoccupied molecular orbital levels. Improved correlations between the adsorption energies and HOMO levels were generated by dividing these molecules into two subgroups: hydroca...