Interplay between Water and TiO2 Anatase (101) Surface with Subsurface Oxygen Vacancy
The interaction between water and the TiO2 anatase (101) surface with a subsurface VO is studied using first-principles calculations.
Upon water adsorption, the relative stability of the subsurface and surface VO reverses. The surface VO becomes energetically more stable than its subsurface counterpart, which induces O to migrate from the subsurface to the surface with a very low energy barrier. Then the adsorbed water molecule can easily dissociate through a barrierless pathway facilitated by surface VO. This reaction pathway has a similar energy barrier with another pathway under which water dissociates with the presence if subsurface VO followed by VO migration from the subsurface layer to the surface layer, indicating that subsurface VO can facilitate water dissociation directly, or, via surface VO indirectly. This novel interplay between the adsorbate and substrate defects may provide a new way to explain the origin of the activity of anatase (101) in photocatalysis in aqueous surroundings.