Study On The Photocatalytic Acitivity Of Titanium Dioxide Prepared By Sol-gel Method

Two kinds of TiO₂ sols(alcohol system and water system) have been prepared, one is using iso-propyl alcohol as solvent and another is water. The TiO₂ film with good stability and high photocatalytic activity has been prepared using the alcohol sol. And the TiO₂ film with photocatalytic activity has been prepared at low temperature using the hydrosol. The experimental results and conclusions are summarized as follows:(1) The sol for TiO₂ films was prepared with tetrabutyl titanate as prescursor, iso-propyl alcohol as solvent, acetylacetone as chelating reagent and nitride acid as catalyst. The TiO₂ film is obtained by dip-coating method.The parameters such as the amount of hydrolysis water, calcining temparature, coating times have been studied on the photocatalytic activity of TiO₂ films for degradation the solution of formaldehyde. The optimum conditions are coating five times, calcining one hour at 450℃ and using the sol of r = 6 (r is the molar ratio of the water to tetrabutyl titanate).The effect of the amount of hydrolysis water on the TiO₂ performance has been analysed by SEM, XRD and TGA.The SEM photos show that the surface of TiO₂ film(r = 6) is rougher than that of the r = 2 sample. TGA curves for TiO₂ dry gels with different water contents (r = 2, r = 6) indicate that it is easier to remove the organic compands from the dry gel of r = 6 than r = 2. XRD measurements show that all the film are pure anatase. The phase transformation temperature for the r = 6 sample was about 60℃ higher than the r = 2 sample.The photocatalytic activity of the TiO₂ film under the sunlight is studied. The result shows that the film has higher photocatalytic activity than Degussa P25 powder, and the film can be reused for many times, so it has the value of practical application.(2) A simple sol-gel route is developed for the preparation of a hydrosol at low temperature(40℃) by hydrolysis of Ti(OBu)4 with acid as catalyst and water as solvent. The TiO₂ film is also obtained by dip-coating method.The photocatalytic activity of the prepared film is studied by the degradation of stearic acid. And the TiO2 film has activity without further thermal treatment. It is important to form TiO₂ film with photocatalytic activity at low temperature on nonthermal resisted substrates such as plastics.The effect of different acid on the hydrosol has been investigated. Using the mixture of nitride acid and acetic acid or nitride acide as catalyst to prepare two different sols, drying them to gain TiC>2 powder, then calcining TiC>2 powder at different temperature. The result shows that the acetic acid can prevent the formation of brookite TiC>2, comparing the two samples, the phase-changing temperature from anatase T1O2 to rutile Ti(>2 is higher using the mixture of nitride acid and acetic acid.Three sols are prepared at different temperature, drying them to gain TiC>2 powder, then calcining TiC>2 powder at 450 "C. The result shows that the content of rutile TiC>2 in the sample decreases with increasing the temperature.