Preparation And Photocatalytic Property Of Metal-nonmetal Co-doped TiO₂ Nanoparticles

TiO₂'s photon utilization efficiency is low and it could be excited only by ultraviolet (UV) source, So S/Fe and S/Zn co-doped nanocrystalline TiO₂ photocatalysts were prepared by hydrothermal method in this paper. The composition and properties of the as-prepared TiO₂ powders were characterized by XRD,XPS,UV-vis DRS,and so on. The factors influencing co-doped nanocrystalline TiO₂ photocatalystic properties were discussed.The results showed that S/Fe co-doped anatase TiO₂ was synthesized by Ti(SO₄)₂, FeCl₃ and thiourea. Sulfur was in the forms of S^2- and SO₄^2-, Fe was in the forms of Fe³⁺ doping in the lattice of TiO₂. The photocatalyst showed excellent catalytic activity under the visible light. Absorbtion in the visible light district was enhanced and the band edge moved to longer wavelength obviously. When the molar ratio of Fe³⁺:S: Ti was 0.005:1:1 , the anatase TiO₂-S-Fe hydrothermally treated at 180°C for 3h exhibited the highist photocatalytic performance. Degradation rate of methyl orange was 32.5% under daylight irradiation for 2h. S/Fe co-doped rutile TiO₂ was synthesized by TiCl₄, FeCl₃ and thiourea. Compared to TiO₂, its binding energy at Ti2p_3/2 raised by 2.0 eV, showed that S, Fe partly replaced the binding position of Ti⁴⁺ with oxygen. Absorbtion in visible light district was obviously strengthened and the catalyst had the strongest absorbtion (λ> 400nm). While the molar ratio of Fe³⁺:S:Ti was 0.025:1:1, the catalyst prepared at 180°C for 2h had the highist catalytic activity. Degradation rate of methyl orange was 70.9% under daylight irradiation for 4h. S/Zn co-doped anatase TiO₂ was synthesized by Ti(SO₄)₂, ZnSO₄ and thiourea .The doping concentration of Zn and pH value of initial solution affected the structure of S/Zn co-doped sample. ZnO was obtained when the molar ratio of Zn:Ti was 1; anatase TiO₂ was obtained when the molar ratio of Zn:Ti was lower than 0.33 under acidic condition while unformed TiO₂ was obtained under alkaline condition and ZnO was not observed. Zn²⁺ may dispersed uniformity on the surface of TiO₂ in the forms of ZnO cluster. When the molar ratio of Zn: S: Ti was 0.16: 1:1,the pH value of initial solution was 5.01, the photocatalyst has the highest activity. Nanosized anatase ZnSO₄/TiO-2 composite photocatalysts was prepared by Ti(SO₄)₂ and ZnSO₄ .The crystallite between 10-20nm. Zn,S were in the forms of Zn²⁺,SO₄^2-, respectively. Absorbtion in the visible light district was enhanced and the band edge moved to longer wavelength. The photocatalyst which was hydrothermally treated under 130°C for 16h had the highest activity, degradation rate of methyl orange was 37% under daylight irradiation for 120min.