Preparation And Photocatalytic Performance Of Graphene/Nitrogen And Sulfur Codoped TiO₂ Composite Photocatalysts

TiO₂ has received much attention as the photocatalytic materials to enhance the photocatalytic efficiency.However,the energy accounted for the absorption wavelength range of TiO₂ only locate at ultraviolet region.Many previous studies have been done to increase the photo-degradation activity by doping non-metal species to narrow the band gap for extending absorption line.Nevertheless,it is so quickly to recombine the photo-generated carriers decreasing the photocatalytic efficiency.In this paper,we intend to enhance the photocatalytic efficiency by using graphene as its high conductivity and specific surface area.Sulfur?S?doped,nitrogen?N?and sulfur?S?co-doped and graphene supported sulfur?S?and nitrogen?N?co-doped TiO₂ were prepared by various methods.The specimens were systematically investigated by TG-DSC,XRD,XPS,FT-IR,Uv-vis.The photocatalytic activity of specimens was characterized by the efficiency of degradation for methyl orange?MO?.The results as follow:?1?Silica gel supported S doped TiO₂(TiO_2-x-x S_x,x=0.03,0.05,0.07)were prepared by ultrasonic copolymerization and hydrothermal method with the Na₂S as the source of S,meanwhile,the photocatalytic activity of specimens was investigated.The results as follow:Ti O_1.95S_0.05.05 exhibited best photocatalytic activity?95%?with the specimens sintered at 700?,and all specimens possessed hypoxia type Ti O₂(Ti₅O₉ and Ti₇O₁₃)structure,and tightly connected with the silica skeleton.?2?Silica gel supported S,N co-doped TiO₂(TiO_2-x-x S_x/2N_x/2,x=0.03,0.05,0.07)were prepared by sol-gel method and hydrothermal autoclave method with HNO₃ and H₂SO₄ as the source of N and S,respectively.The results as follow:TiO_1.95S_0.025N_0.025.025 presented best photocatalytic efficiency when the specimens were sintered at 700?,and all specimens were single anatase structure with highly crystalline.Furthermore,we change the content of TiO_1.95S_0.025N_0.025decorated on the same content of silica gel.The photocatalytic efficiency increased initial and then decreased,which strongly depend on the sintering temperature and attached TiO_1.95S_0.025N_0.025.025 content.TiO_1.95S_0.025N_0.025.025 exhibits the highest photocatalytic efficiency among the specimens?96%?.?3?GO supported S,N co-doped TiO₂(TiO_2-x-x S_x/2N_x/2,x=0.03,0.05,0.07)were prepared by sol-gel method and hydrothermal method with HNO₃ and H₂SO₄ as the source of N and S,respectively.The result was shown below:The specimens sintered at 700?showed the highest photocatalytic activity among the components.GO introduction can effectively decrease the degree of aggregate for doped TiO₂ by increasing its specific surface area.The band gap was narrowed by the S and N introduced,which benefited for the separation of photogenerated electrons-hole pairs.GO could move the photogenerated carriers quickly hindering its recombine for enhancing the photocatalytic activity.Those results showed that the optimum content of GO was 1.5%(GO-TiO_1.95S_0.025N_0.025)exhibits the highest photocatalytic efficiency among the specimens?98%?.