Molecular adsorption and dissociation of CO₂ on TiO₂ anatase (001) activated by oxygen vacancies

A study on the influence of oxygen vacancies on the anatase (001) surface on the CO₂ adsorption process is presented. For its realization, density functional theory (DFT) was used under the Perdew-Burke-Ernzerhof (PBE) generalized gradient and the spin-polarized approximations. Hubbard-U corrections and van der Waals interactions were also included. Three different types of oxygen vacancies were investigated at different sites on the anatase (001) surface; the formation energies in each case were 67.05, 113.84, and 93.16 kcal/mol, respectively. We identified a type of oxygen vacancy that could favor both the CO₂ adsorption and dissociation. The differences on CO₂ adsorption properties are due to electronic and structural causes, such as midgap states (Ti³⁺ polarons species) and changes in the structural properties on the TiO₂ surface, generated upon the introduction of an oxygen vacancy. It is concluded that oxygen vacancies can play an important role in both CO₂ adsorption and dissociation.