Preparation Of Nonmetal Codoped TiO₂ And Their Characteristics

B-S-codoped TiO₂ nanoparticle, N-S-codoped TiO₂ nanoparticle and nanotube had been prepared by hydrothermal method using starting materials Ti(SO₄)₂ as Ti source and other materials as nonmetal dopants. Their characteristics were investigated by XRD, UV-vis, XPS and photocatalytic activity.B-S-codoped TiO₂ nanoparticle (T1O2-B-S) was prepared using Ti(SO₄)₂ with H₂SO₄ as S source and H₃BO₃ as B source. XRD indicated that it was anatase, doping of B and S can resist the growth of its crystal size. UV-vis showed that its absorption in the visible light district was strengthened and the band edge moved to longer wave obviously. XPS showed that the content of hydroxyl group on its surface increased, compared with that of B or S-doped TiO₂, which favored its photocatalysis. Its activity was evaluated by decomposing methyl orange, the results indicated that TiO₂-B-S prepared at 240℃for 12 hours exhibited the highest photocatalytic activity, the degradation ratio of methyl orange were 99.8 % and 80.0% under UV light and sunlight irradiation, respectively. The higher visible light photocatalytic activity of B-S co-doped TiO₂ was attributed to the doped boron that lowered the band gap, resulted in the localized crystal deformation and the doped sulfur which enhanced the surface acidity of TiO₂. Doping of B and S possessed the synergistic effects on enhancement of TiO₂ photocatalytic activity.N-S-codoped TiO₂ nanoparticle(TiO₂-N-S) was prepared using Ti(SO₄)₂ with thiourea as N,S sources. XRD showed that it was anatase with good crystallinity. A red shift of the absorption edge was brought out owing to N and S codoping, and the extension for photoabsorption range of it occurred. EA studies showed that N concentration decreased from the surface to the center. Especially, the photocatalytic tests indicated that it demonstrated a high photocatalytic activity for decomposition of methyl orange, comparing to S doped TiO₂ and undoped TiO₂ .The degradation ratio of methyl orange were 88.2 % and 41.4% under UV light and sunlight irradiation, respectively. The high activity of it can be related to the results of the synergetic effects of strong absorption in the UV-vis light region, red shift in adsorption edge, oxygen vacancies and the enhancement of surface acidity induced by N and S codoping.N-S-codoped TiO₂ powders were prepared using Ti(SO₄)₂ as Ti and S sources, ammonia as N source, respectively. N-S-codoped TiO₂ nanotube(TiO₂-N-S nanotube) was synthesized by hydrothermal method using N-S-codoped TiO₂ powders with 10M NaOH. It could be deduced that the formation of TiO₂ nanotube was related to the hydrothermal reaction temperature and time, washing process and the pH value of washing solutions. When the pH value was 7, TiO₂ nanotubes were prepared at 160℃for 24 hours with its length about 1800nm and its inner diameter about 50nm; when the reaction temperature was over 160℃, TiO₂ nanostick and nanobelt appeared. TiO₂-N-S nanotube, prepared at 110℃for 24 hours with length about 1500nm and inner diameter about 20nm, was mixed crystal containing anatase and rutile TiO₂- XPS testified that N, S were in the form of Ti-N and S-S, respectively. UV-vis indicated that the visible absorption of nanotube was higher than that of TiO₂ nanoparticle. The photocatalytic activity of TiO₂-N-S nanotube was higher than that of TiO₂ nanotube under UV irradiation.