Preparation, Structure And Property Of Anatase Crystalline Sol

The research of TiO₂ has attracted more and more scientists since Fujishima and Honda published a thesis named "Electrochemical Photolysis of Water at a Semiconductor Electrode" in Nature magzine. Lots of work concentrate on the preparation of nano TiO₂ powders with high photocatalytic property, multiphase photocatalytic mechanism, enhancing quantum-efficiency of T1O2. However, seldom reports can be found about the chemistry mechanism of synthesis T1O2 sol through Sol-Gel method, and the influence of technics on the structure and photocatalysis performance of TiO₂ sol. Based on the past research, an approach to the low-temperature preparation of anatase TiO₂ was proposed in this paper, and the improvement of this preparation technics was also presented.The TiO₂ sol is prepared through Sol-Gel method, Ti(OC₄H₉)4 is chosen as a precursor, and ethanol as impregnant,HCl as catalyzer. A new reaction system and the according technical route were explored, and TiO₂ sol containing anatase crystals was prepared at low temperature(under 20-80℃), which possesses direct photocatalytic property without the traditional high-temperature heat-treatment in the powders and films research. Anatase TiO₂ sol is prepared using Ti(OC₄H₉)₄, H₂O, system with mol ratio of 1:100-200. The new reaction system and the according technical route ensure the precursor hydrolyzes thoroughly.The author studied the hydrolyze, aggregation and crystalline course of Ti(OC₄H₉)₄ in water.Also studied the relationship between preparing conditions with structure and property.The results of the hydrolyze course of Ti(OC₄H₉)₄ in water showed that Ti(OC₄H₉)₄ was completely hydrolyzed in excessive water.Then inorganic titania colloidal particles formed. The particles assembled loosely at first. With the growth, congeries became more and more dense and shape-regular, and formed cubic anatase crystal finally.The relation between prepare conditions with structure and property:(1) TiO₂ sol contained perfect anatase crystals and possessed great photocatalytic property when the sol prepared with mol ratio of H₂O:Ti(OC₄H₉)₄>64:1. In addition, the anatase crystals and photocatalytic property was improved with the increase of the quantity of water, when content of solid was invariable.(2) The crystals in TiO₂ sol were different in various pH conditions. If pH<1, the sol contained rutile, anatase and a little brookite crystals;if l10,there was only brookite crystals in the sol. The sol made in the strong aciditycondition had the best photocatalytic property.(3) The TiO2 sol was prepared in excessive water and aginged in a waterbath under different temperatures(20°C, 40°C.. 60°C > 80°C). When the aging temperature rised, the big crystals grow more perfect, which was accordant to the enhanced photocatalytic property. In addition, the results showed that there are red shifts for the edge of the crystals absorption curves when the aging temperature rised, which means that the forbidden gap gets narrower.(4) The coordination number of Ti increased with the increase of the sol aging time and finally closedto the coordination number of anatase type. And thephotocatalytic property was stably enhanced until the sol stabile.