Preparation Of TiO₂ Films Via Surface Dielectric Barrier Discharge At Atmospheric Pressure

TiO2 is an innocuous and chemically stable semiconductor photocatalyst of high photocatalytic activity. Under the irradiation of UV light, TiO2 exhibits high photocatalytic activity and good hydrophilcity. Accordingly, it is widely used in photocatalysts, antibacterial films, self-cleaning films and solar cells, etc, and many researches focus on it in the subjects of enviroment and energy. TiO2 film can be prepared via a lot of methods, howerver, in traditional liquid phase processes, such as sol-gel, the TiO2 film is prone to crack, and plenty of exhausted liquid discharge may polute the enviroment. On the other hand, low pressure gas phase processes like sputtering, etc, need to be performed in vacuum, the expriment setups are very complicated and the cost is fairly high. Comparing with other methods, atmorspheric pressure low temperature plasma enhanced chemical vapor deposition is a promising technology, which has individual advantages and is potential to be industrialized.In this work, uniform TiO2 films were deposited on moving plastic and glass substrates through atmospheric pressure plasma enhanced vapor deposition method from TiCl4 and O2 using surface dielectric barrier discharge. The photocatalytic application of TiO2 films in removing HCHO from simulated air was examined. Meanwhile, influents of RH and total air velocity index on the photocatalytic application, and effects of discharge power, deposition time, post-treatment method and the addition of N2 on the photocatalytic activity of the TiO2 films were investigated. Furthermore, Crystal forms and optical properties of TiO2 films were investigated by XRD, Raman spectra, SEM and UV-Vis spectra. In addition, the discahrge system was diagnosed by emission spectrum.It indicated, the TiO2 films deposited on moving substrates were more uniform than those deposited on motionless substrates. With the increase of discharge power or extension of deposition time, the weight of the as-deposited TiO2 films increases, meanwhile the photocatalytic activity of the TiO2 films improves, and with the increase of the weight of the as-deposited TiO2 films, the photocatalytic activity of the TiO2 films enhances and reaches a certain value gradually. A certain amount of N2 addition into the reactant gases may lead to a higher photocatalytic activity of the TiO2 film, which was consistent with the results of Raman analysis. In our work, the of TiO2 film prepared with 1% N2 addition showed the highest photocatalytic activity, just increased about 20% compared with those deposited with no N2 addition. It was found that the TiO2 would show extremely low photocalytic acivity while chilled quickly to room temperature from 450℃after calcination for 2 h. Analysized by Raman spectra and SEM, it was found that the crystal forms of TiO2 films prepared via quick chilling and slow cooling were almostly consistent, but the surface topography was rather different.