MODIFICATION OF TITANIUM DIOXIDE WITH NITROGEN, SILICON, AND CARBON FOR VISIBLE LIGHT PHOTOCATALYSIS

Abstract

Titanium dioxide and nitrogen-silicon-codoped titanium dioxide were prepared by two different ways. The first method was prepared by using nitrogen as a nitrogen source and silicon-containing chemical as a silicon source via solvothermal- and sol-gel-made photocatalysts. The nitrogen-silicon-codoped titanium dioxide showed the highest photocatalytic activity under both UV and visible light irradiation. The addition of silicon resulted in the formation of partial monolayer of silicon on titanium dioxide and an increase of the anatase phase stability. The annealing atmosphere affected the distribution concentration of surface and interface species such as surface oxygen and Ti3+ sites, thus improving photocatalytic activity. Moreover, the other method was prepared by using aminopropyltriethoxysilane (APTES) via hydrothermal method. As results, the monolayer and/or multilayer amino-silane coverage on titanium dioxide surface substantially decreased the indirect band gap, leading to the formation of silicon-nitrogen intermediate level within band gap and suppressing the electron-hole recombination. It subsequently enhanced the photoactivity. With increasing APTES contents, the hydrophilic property was decreased whereas the formation of amine group and the oxygen chemisorption were apparently increased. However, the difference in APTES concentration significantly affected the hydrophobicity. The reduction in protonated amine played an essential role in the retarding of photoactivity. In addition, the present work also describes the use of pulsed direct current magnetron sputtering for the deposition of carbon-doped titanium dioxide thin films, using carbon dioxide as the carbon source. It was found that, though carbon-doping resulted in improved dye degradation compared to undoped titanium dioxide, the UV-induced photoactivity of carbon-doped photocatalysts was lower for model pollutants used. Finally, the grafting of titanium dioxide on PMMA film via atom transfer radical polymerization (ATRP) was also studied. As a result, a method of grafting process was successfully completed and confirmed by various techniques. The photocatalytic activity was evaluated under UV light irradiation. The TiO2-g-PMMA films was reused at least 5 times.