Influence of the molecular adsorption of CO2, CO and NO on the stability of oxygen vacancies on the anatase TiO2 (101) surface

Abstract

The impact of the molecular adsorption of CO₂, CO and NO on the stability of oxygen vacancies at the anatase TiO₂ (101) surface is studied through first-principles calculations. Our findings reveal that the adsorption of CO₂, CO, and NO stabilizes the surface oxygen vacancy relative to the subsurface vacancy, with total energies being 0.08 eV, 0.32 eV, and 1.58 eV lower, respectively. This suggests that the adsorption of these molecules can thermodynamically reverse the relative stability between the surface and subsurface oxygen vacancies, with the surface oxygen vacancy surface becoming the most stable. Additionally, we investigate the kinetic effects of oxygen vacancy interactions with small molecules. The diffusion barriers for oxygen vacancies on surfaces with adsorbed CO₂ and CO are found to be 0.68 eV and 0.36 eV, respectively—significantly lower than the diffusion barriers on the clean surface by 0.16 eV and 0.50 eV, respectively. These results suggest that CO adsorption can effectively promote the diffusion of oxygen vacancies. Overall, this study highlights the crucial role of molecular adsorption in modulating the stability and interaction of oxygen vacancies on the anatase TiO₂ (101) surface, providing insights into the photocatalytic activity of this material.