(421o) Preparation of Visible Light Absorption Enhanced TiO2 By Atmospheric Pressure Water Vapor Plasma

Although titanium dioxide (TiO2) is one of the most commonly utilized photocatalyst, since it absorbs only ultraviolet light, utilization efficiency of solar light is very low. Therefore, many approaches including nitrogen doping have been tried to narrow the band gap and to absorb visible light. However, although these approaches succeeded to improve visible light absorption efficiency of TiO2, response to visible and infrared irradiation is still not sufficient. On the other hand, Chen X. et al. reported a different approach to enhance solar light absorption by introducing disorder in the surface layers of nanophace TiO2 through hydrogenation under high-pressure hydrogen atmosphere. Pranevicius L. also reported on the preparation of hydrogenated TiO2 using magnetron sputter-deposition technique. The obtained hydrogenated TiO2 showed dramatically improved visible and infrared light absorption, however, severe experimental condition or special equipment are required in these process.
In this report, we developed a new preparation method of visible light
absorption enhanced TiO2 using atmospheric pressure water vapor plasma. In the experiment, a newly developed apparatus in which a cylindrical type porous ceramic filter and non-thermal plasma were combined was used. The apparatus was originally developed to decompose gaseous or water pollutants using atmospheric non-thermal plasma, however, it was modified in many ways to treat TiO2 powder. Amorphous TiO2 (<0.05µm) was treated by atmospheric pressure water vapor plasma at 70 W of discharge power for
1hr. X-ray diffraction pattern of the obtained sample indicated that amorphous TiO2 changed into mostly anatase TiO2 and small portion of rutile TiO2. The sample also exhibited gray color and enhanced visible light absorption. These results indicated that the newly developed method using atmospheric pressure water vapor plasma could prepare TiO2 powders with enhanced visible light absorption property under relatively mild conditions.