Density Functional Theory Calculations of Oxygen-Vacancy Formation and Subsequent Molecular Adsorption on Oxide Surfaces

The surface oxygen vacancy formation energy (E-Ovac) is an important parameter in determining the catalytic activity of metal oxides. Estimating these energies can therefore lead to data-driven design of promising catalyst candidates. In the present study, we determine E-Ovac for various insulating and semiconducting oxides. Statistical investigations indicate that the band gap, bulk formation energy, and electron affinity are factors that strongly influence E-Ovac. Electrons enter defect states after O desorption, and these states can be in the valence band, mid-gap, or in the conduction band. Subsequent adsorption of O-2, NO, CO,CO2, and H-2 molecules on an O-deficient surface is also investigated. These molecules become preferentially adsorbed at the defect sites, and E-Ovac is identified as the dominant factor that determines the adsorption mode as well as a descriptor that shows good correlation with the adsorption energy.