Synthesis Of Bi₃Ti₂O₈F Photocatalyst And Its Surface Modification

Surface modification of photocatalysts has become one of the most effective methods to enhance their photocatalytic activity. Nonmetallic elements including F have been widely used as the surface modifiers. Surface fluorination has proven effective in enhancing the activity of TiO2-based photocatalysts but endures the shortcoming of harsh preparation conditions and poor stability. In this work, we report a new semiconductor photocatalyst, Bi3Ti2O8F (BTOF) and speculated that this oxyfluoride photocatalyst would has abundant and stable surface F atoms, which might endow BTOF with desired surface properties and photoactivity.In this experiment, we carried out the research on synthesis route, surface properties and the photocatalytic activity of BTOF. More details are listed below.1. We synthesized BTOF powders via a facile hydrothermal route for the first time, which exhibit high purity, good crystallinity and large specific area. BTOF nanoparticles have a structure of a three-dimensional network, producing abundant plenty of open space.2. BTOF has desirable surface properties. It has abundant surface Ti-F groups, strong surface electronegativity and much larger adsorption capacity for cationic dyes than F-TiO2 and pure TiO2.3. We have demonstrated that BTOF is a superior photocatalyst in degradation of dyes, which can decompose cationic dyes more quickly than TiO2 in both UV and visible irradiation through the dye photosensitization effect. However, BTOF doesn’t show any intrinsic photocatalystic activity at all.To enhance the intrinsic photocatalytic activity and utilization of visible light of the prepared BTOF, we conducted the further research as below.4. We treated the BTOF powders with KI solution at acidic pHs and the results indicated that the I-ions could be easily bonded to BTOF surface through a simple ions exchange reaction. More importantly, the intrinsic photocatalytic activity of KI treated BTOF was largely enhanced.5. To increase the visible-light adsorption of BTOF, we doped BTOF by adding I-ions during the process of hydrothermal growth. As a consequence, the adsorption of visible light (350 nm<X<450 nm) of BTOF was largely increased. Moreover, the KI-treated BTOF also exhibited better visible-light adsorption (330 nm<λ<600 nm).