Synthesis Of Multiphasic Titanium Dioxides At Low Temperature And Research Of Their High Photocatalytic Activities

Titanium dioxide (Titania) as a important inorganic material, there has been increasing applications in pigment, cosmetics, fine ceramics, solar cells, and particularly, photocatalysts for mediating difficult-to-remove pollutants in wastewaters generated from textile industry, because of its low cost, non-toxicity, high stability and high efficiency. Although titania has been overwhelmingly studied as perhaps the most effective photocatalyst, lack of highly catalytic activity still limits its capability to treat most refractory organic pollutants. This is one of the key issues that hamper industrial application. The photocatalytic efficiency of titania are strongly dependent on the crystalline structure, morphology and size of the particles. Conventionally, titania catalysts are synthesized by sol-gel method followed by calcination at elevated temperatures. The heat treatment step is accompanied by sintering, grain growth, and loss of surface area on catalyst particles that are known to reduce catalytic activities. Hydrothermal method has also been explored as a synthetic route to prepare catalysts, with sacrifice of higher pressure for lower temperature than encountered in calcinations. In general, these methods lead to large particle size, lack of surface defect, and as a result low photocatalytic activities, one approach with growing popularity is controlling nano-titania particle size by avoiding high temperature calcinations or high pressure, as large surface area on catalysts is pursued for high catalytic activity. The synthetic work at lower temperature——Low temperature synthesis, has been an new research.In the paper, titania with high photoactivities were synthesized via two different synthetic route at low temperature and ambient pressure throughout preparation process. Method 1 is an improved sol-gel method. Water, instead of alcohol as the solvent and by hydrolysis Ti(OC₄H₉)₄ in HNO₃ solution at low temperature. After boiled at 100℃ for hours, Nano-TiO₂ powders of different forms were prepared. Method 2 is low-temperature-calcination. Additive, such as urea or ammonia bicarbonate was concerned with the synthetic reaction, respectively. After calcinations at 300 °C for 2 hours, "anatase+rutile","anatase+brookite" titania were synthesized.