Preparation Of TiO₂Photocatalytic Films Using Cold Plasma Chemical Vapor Deposition At Atmospheric Pressure

TiO2thin films with high photocatalytic activity, chemical stability, are widely used in gas purification, sewage treatment, antimicrobial, sterilization and solar cells etc. The traditional methods to prepare TiO2photocatalytic film need heat treatment at high temperatures which are unfavorable to thermally sensitive substrate. Plasma chemical vapor deposition is highly efficient for low-temperature fabrication. However, it is used at low pressure which needs vacuum systems. Dielectric barrier discharge is a simple and easily operated approach for generating atmospheric-pressure cold plasma.In this paper, TiO2photocatalytic films were deposited through atmospheric pressure cold plasma chemical vapor deposition method from TTIP and O2using dielectric barrier discharge. This paper studied the effects of heat treatment (350℃or450℃) and preparation conditions (TTIP partial pressure, O2partial pressure, input power and deposition time) on the photocatalytic activity of TiO2films. The photocatalytic activity of TiO2film in removing HCHO from simulated air was examined. Structure and properties of TiO2film were investigated by Raman spectroscopy, FT-IR spectra, UV-Vis spectra, AFM. Furthermore, this paper investigated the vibrational temperature and rotational temperature of the discharge system using OES spectra and SPECAIR software.Raman spectra showed that the TiO2films one-step deposited were amorphous structure, the FT-IR spectra showed that the films had OH group, so this paper speculated that these films were amorphous structure of Ti-OH which showed a photocatalytic response. The photocatalytic activity of TiO2films without any treatment was significantly higher than the heat-treated films (350℃or450℃). The FT-IR spectra results showed that the OH content of the heat treatment TiO2films reduced. When the TiO2films were calcined at450癈, the characteristic peaks corresponding to anatase TiO2were observed and the crystal was responsible for photocatalytic activity. UV-Vis spectra results showed that the absorbance of the TiO2thin films after heat treatment at300～350nm were lower than the untreated films. The atomic force microscopy showed that the surface roughness of the TiO2thin films one-step deposited was2nm and decreased after heat treatment which resulted the decrease of photocatalytic activity. This paper investigated the impact of experimental conditions (TTIP partial pressure, O2partial pressure, input power and deposition time) on the photocatalytic activity of the TiO2films. The FT-IR spectra results showed that the variation of OH content with the changes of experimental conditions was as the same as the variation of photocatalytic activity. This showed that OH group on film surface was a important factor of the photocatalytic activity. SPECAIR software fitting results showed that TTIP partial pressure and O2partial pressure had little effect on the vibrational temperature and rotational temperature. Furthermore, when the input power was increased, the vibrational temperature of the discharge system reduced and the rotational temperature rised.