Synthesis of Nano-Scale TiO2-XNX Powder by Two-Emulsions Method and its Photocatalytic Properties

• Main Authors: Yin-Hsia Ling, 凌銀霞
• Other Authors: Wen-Duo Yang
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/22263009746251128640

碩士 === 國立高雄應用科技大學 === 化學工程系碩士班 === 94 === Nanometric-sized nitrogen-doped titanium oxide (TiO2-xNx) powders have been synthesized successfully through two emulsions method. In which two solutions of reverse emulsion, one containing Ti4+ chelated with acetylacetone aqueous droplets and the other aqueous ammonia droplets, with the same water/oil (w/o) ratio and mixed together to form a slurry of titania precursor. Then the precursors were recovered and calcined in NH3 atmosphere to form TiO2-xNx. However, the precursors were characterized by FTIR, DTA/TGA and XRD etc., and those mechanisms for the evolution of crystalline powders in two emulsions method have been proposed and discussed in the context of the microstructure. A photocatalytic degradation experiment of methyl orange was efficiently decolorized in the presence of the TiO2-xNx powder by exposing its aqueous solution to visible or ultraviolet light. It was found that the anatase phase is formed at 400 oC and converted to rutile phase as heat-treated at 700 oC. The synthesized TiO2 powders exhibits particle sizes at 10-30 nm, specific surface area about 30-95 m2/g. Furthermore, the surface response method (include Box-Behnken design) was applied to deal the preparatory conditions of the two emulsions process. It reveals that the optimal preparatory conditions were obtained at the volume ratio of surfactant/n-hexane = 0.03, volume ratio of water =0.04, molar ratio of acetylacetone/titanium isopropoxide=4, molar ratio of isopropanol/ titanium isopropoxide = 23.1. By combining the optimal settings of those variables, it has been obtained a nanometric-sized TiO2 powder with specific surface area at 91 m2/g. The colour of TiO2-xNx is yellowish, different from the TiO2 of white, in evidence of the successful preparation, and demonstrates the binding energy centered at 399 eV examined by XPS. Additionally, the suitable particles size remarkably enhance the photocatalytic activity of TiO2-xNx in visible light has been also investigated.