Effect of phase structures on the photocatalytic activity of surface fluorinated TiO₂

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• 作者：Kangle Lv ; Xiaofang Li ; Kejian Deng ; Jie Sun ; Xianghong Li ; Mei Li
• 关键词：Photocatalytic degradation ; Titanium dioxide ; Fluoride ; Adsorption ; Crystalline phase
• 刊名：Applied Catalysis B: Environmental
• 出版年：2010
• 出版时间：6 April 2010
• 年：2010
• 卷：95
• 期：3-4
• 页码：383-392
• 全文大小：1035 K

文摘

Nanocrystalline TiO₂ with different contents of anatase were tailored by hydrothermal treatment of the mixed solution of Ti(SO₄)₂ and TiCl₄ at 250 °C for 24 h, and then calcined at 500 °C for 3 h. The catalysts were characterized by X-ray diffraction, transmission electron microscopy, nitrogen sorption, X-ray photoelectron spectroscopy and UV–vis diffuse reflectance spectra. The as-prepared TiO₂ samples with different contents of anatase have similar BET specific surface areas (30–40 m²/g) and crystalline sizes (30–40 nm). The effect of surface fluorination on the adsorption and photocatalytic activity of TiO₂ samples was evaluated using Brilliant Red X3B, an anionic azo dye, as the target organic molecule at pH 3.0. Both on anatase and rutile TiO₂, the dark adsorption of X3B was greatly decreased in the presence of fluoride, ascribed to competitive adsorption of fluoride that reduces the positive charges on the catalyst surface. After surface fluorinated by 1.0 mmol/L NaF, the photocatalytic activity of anatase was enhanced by a factor of 2.63. However, 81.3 % of the photocatalytic activity was reduced for rutile TiO₂ after surface fluorinated under the same condition. Only when the content of anatase is higher than 40 % , can fluoride shows positive effect on the photocatalytic activity of TiO₂. Two reaction models were put forward, based on the photocurrent response, degradation kinetics, hydroxyl radicals quenching and detecting, to illustrate the different effects of fluoride on the photocatalytic degradation of X3B in anatase and rutile TiO₂ suspensions.