The Theoretical Study Of The Electronic Structure And Surface State Of Modified TiO₂(110) Surface

The modified methods containing deposited metals, doped transition metals ion and nonmetal element were adopted to enhancing the catalytic activity of TiO₂。For revealing the mechanism of surface reactivity and synthesizing new compound photo catalyst ,it is necessary to study the surface electronic structure of modified TiO₂ (110) surface. The systemic study of surface electronic structure of oxygen defect and modified TiO₂ (110) surface was performed by using the cluster and periodic slab model at DFT-B3LYP level. In this work, the stable deposited sites were confirmed, and the orbital essence of different surface states induced by oxygen defect, alkali metals and transition metals deposited and Cr doping on TiO₂ (110) surface and its catalytic reactivity mechanism were revealed. The calculated result as follow: 1. The visible relaxation of TiO₂ (110) defect and perfect surface has been showed. When the O2 adsorption on relaxation TiO₂ (110) defect surface, the active species O₂^2-and O₂^-were formed and induce the strong ability of oxidation. This result reveal the essence of active surface state and the photocatalysis on theoretical level. 2. Alkali atoms(AM) prefer to bind on "adjacent"site on perfect TiO₂ (110) surface. 3s electron of Na transfer to 3d orbital of Ti(5f), which leads to spin-polarize state at band-gap of perfect surface. The new form of surface state different from that of oxygen defect surface was found firstly. Its active site is Ti(5f) whereas the Ti(4f) of oxygen defect surface. NO adsorption on AM/ TiO₂ (110) surface via O atom bound to Ti(5f) can promote the cleavage of bond of N-O. 3. Post-transition metals(Cu,Ag,Au,Ni,Pd,Pt) prefer to bind on top of bridging oxygen of perfect TiO₂ (110) surface, leading to create new active surface state different from that of oxygen defect surface and AM/ TiO₂ (110) surface. These metals are active sites for deposited system. This surface state can promote the activity of catalytic dissociation of NO and CO for TiO₂ (110) surface. 4. Ti,V,Cr,Mn,Fe,Co also prefer to bind on top of bridging oxygen of perfect TiO2 (110) surface, leading to create same active surface state as mentioned above. The energy band of d of deposited metals descend to EF from left to right on elemental periodic table, later the energy band of d of Co appear in the bonding area 5. Doping Cr into perfect TiO2 (110) surface can create the new active surface state different from that of oxygen defect surface ,AM and transition metals deposited TiO2 (110) surface. Its active surface state is the Cr 3d occupied state near EF and the value of band-gap drop from 3.13eV to 1.16eV, so photocatalysis reaction can perform in visual light area after doping Cr into perfect TiO2 (110) surface.