The Reactivity of Anatase TiO2 (211) Surface and the Bond- Charge Counting Model

In this chapter, we intend to present a generic understanding of surface reactivity and water dissociation on TiO2 surfaces through a study of anatase TiO2 (211) surface—an idea model surface containing both four-coordinated Ti atom (Ti4) and five-coordinated Ti atom (Ti5). Our first-principles calculations show that the (211) surface is a high reactivity surface and reveal that water molecule can be easily dissociated on a Ti4 site while it hardly dissociates on Ti5 site. Furthermore, we introduce bond-charge counting model to clarify the mechanism. More generally, after an intensive investigation of literature, we found that the bond-charge counting model is applicable to all anatase and rutile TiO2 surfaces including step edges and vacancies where the reactivity of surfaces enable to dissociate water attribute to the existence of Ti4 atom or equivalent Ti4 atom