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The Characteristics and Photocatalytic Activity of Visible Light Driven N-doped TiO2

H-J Hsu, Y-T Lin and Y-H Lin
National Chung Hsing University, TW

Keywords: visible light, n-doped TiO2, photocatalysts, calcinations, ethylene

Abstract:

In the recent decades, titanium dioxide (TiO2) nano-material was received widely attention because of its good chemical stability, low-toxicity, self-cleaning, anti-bacteria and deodorant. However, its photocatalytic activity was limited only by ultraviolte (UV) light irradiation due to the high energy band gap, low photo quantum efficiently, high recombination rate of electron-hole pairs, and known that UV light account for about 5 % of solar energy. Previous studies demonstrated the mechanism of modification to titania varied with synthesis methods. Doping of non-metal could narrow down the band gap, suppress the recombination of photo-induced electron-hole pairs, whereas the doping transition metal might produce poor due to the thermal instability, its need of an expensive ion-implantation facility or the growth of carrier trapping. Therefore, doping TiO2 with non-metal elements has received much attention. Recent studies have shown that nitrogen can improve the photoactivity of TiO2, inhibit phase transformation form anatase to rutile, and stimulate adsorption of organic molecules on the catalysts surface. Beside, N-doped TiO2 was capable of lowering the band gap, shifting the optical response to the visible light region and decreasing the recombination rate of photogenerated electron-hole pair. There were few reports on the discussion of various molar ratio (ammonia/TTIP) of N-doped TiO2, and various calcination temperatures, without incorporate discussion for sample’s variety of crystalline. Thus, we focus on the sol-gel synthesis of N-doped TiO2 at various ammonia/TTIP molar ratio (0.0 ~ 3.0) and calcination temperatures (400 ~ 800 °C). Samples were analyzed by XRD, UV-Vis, TEM, BET and DTA-TG in order to understand the characteristics of N-doped TiO2. The photocatalytic oxidation reaction activity of N-doped TiO2 were evaluated for the decomposition of the ethylene under the visible light irradiation. The result indicate the major peak of crystallite plane of anatase and rutile for temperatures showed 400°C and 700°C, respectively. The N-TiO2 samples revealed the significant red shift of the absorption edges. When the temperature increasing, the percentage of weight (%) displayed decreasing. Lastly, the N-TiO2 exhibited much higher photocatalytic activity of photodegradation of ethylene than pure TiO2 under visible light illumination.
 
 
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