The effects of subsurface O_v and Ti_int of anatase (1 0 1) surface on CO₂ conversion: A first-principles study

Using the first-principles calculations, we explored the effects of intrinsic subsurface oxygen vacancy and Ti interstitial defects on the adsorption and reduction reaction of CO₂ at anatase (1 0 1) surface. Both PBE + U and HSE06 results show that such intrinsic defects have strong selectivity for the CO₂ binding to sites near the defects. For the most favorable site, the CO₂ adsorption energy can be greatly increased by 0.06 – 0.2 eV relative to the perfect surface. This enhancement is greatly affected by the local structure distortion and the location of the excess electrons. Furthermore, the reduction reactions of CO₂ into useful fuels such as HCOOH have also been explored. It is revealed that the energy barrier for the rate-limiting step of CO₂ activation can be greatly lowered by the intrinsic defects. These results show the important effects of the defects on the CO₂ adsorption and reduction processes.