A preliminary research on V/N–TiO2 self-cleaning thin film by sol–gel method under the guidance of first principle method density functional theory (DFT)

A series of Ti1−xVxO2−yNy self-cleaning thin films, which can be activated driven by visible-light (VL), have been successfully immobilized on quartz glasses by sol–gel and dip-coating methods. The First Principle Method acts as guidance and reference for getting the critical (up-limitation) vanadium doping quantity in accordance with the binding energy change. Results of the band structure calculations and the doped density of states (DOS) reveal that localized impurity bands obviously existed in the band gap of TiO2 when the V doping quantity was ca.6 at%, this film possesses the optimal visible light absorption by facilitating the transition of electron from the localized impurity band to the conduction band. Anatase crystalline phase was detected by the characterization of X-ray diffraction (XRD). TG/DTA, AFM, XPS, UV–vis, MB degradation and surface contact angle (CA) tests were also conducted for the film structural and optical properties. It is found that the mean square root (RMS) roughness of Ti0.94V0.06O1.94N0.06 (13.9 nm) is ca.33 times than the others, the V, N mono-doping can increase visible light absorption (403 nm), while V/N co-doping can greatly enhance absorption in lower frequency visible region (496 nm). The MB degradation rate of Ti0.94V0.06O1.94N0.06 is 7.7 × 10−3 mol L−1 min−1, while the rates of N-doped and pure TiO2 film were (1.94 × 10−3 mol L−1 min−1) (0.8 × 10−3 mol L−1 min−1), respectively. The CA on this kind of film can approach to ca. 5°. All these results indicated that the Ti1−xVxO1.94N0.06 does well in photocatalysis and photohydrophilicity within the region of visible light. It would be a promising practical self-cleaning function and application.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The doping up-limitation of vanadium in TiO2 was derived by the binding energy change. ► The greatest RMS (13.9 nm) self-cleaning film possesses impurity band between the VB and CB was successfully prepared. ► The photocatalytic and wetting properties were studied upon UV and Vis irradiation. ► V/N–TiO2 films show superior self-cleaning activity. ► The mechanisms have been elaborated for this photoreaction.