PHOTOCATALYTIC ACTIVITY OF NITROGEN AND FLUORINE CO-DOPED TITANIUM DIOXIDE PREPARED USING OF VARIOUS PH SOLUTIONS

Introducing different atoms into TiO₂ crystal lattice is a famous method to improve photocatalytic activity of TiO₂ under visible-light irradiation. In this paper, Nitrogen (N) and fluorine (F)co-doped TiO₂ powders were prepared by mixing TiCl₃ solutions with ammonium fluoride (NH₄F). In preparation, we used NH₃-H₂O solution for adjustment of pH values (pH 2, 7, and 9) of mixed solution. X-ray diffraction (XRD) indicated N,F-TiO₂ powders prepared at pH7 and pH9 contained only anatase phase, but the powders prepared at pH2 contained both anatase and rutile phase. The result of XRD also indicated N,F-TiO₂ powders prepared at pH7 had the smallest crystallite size. We measured photocatalytic activity of prepared N,F-TiO₂ powders by the decomposition of methylene blue. N,F-TiO₂ powder prepared at pH7 and pH9 showed same high photocatalytic activity under ultraviolet light irradiation (peak wave length = 352 nm). Furthermore, under green light LED irradiation (wave length = 525 nm), a sample prepared at pH7 decomposed methylene blue more quickly than any other samples. As the result, N,F-TiO₂ prepared at pH7 had the best catalytic activity under both UV-light and visible light in the all of N,F-TiO₂ prepared and reference TiO₂ photocatalyst (ST-01 produced by Ishihara Co. Ltd).