Synthesis And Photocatalytic Activity Study Of Doped And Composites Tungsten Trioxide Nanomaterials

Photocatalytic technology is a kind of environmental pollution treatment technology which can deal with most pollutants in water by using only solar energy without other energy.It is considered as a technology with great application prospect.Tungsten trioxide?WO₃?has received extensive attention due to its environmental friendliness,photochemical stability and excellent visible light absorption properties.In this paper,sulfur doped tungsten trioxide nanomaterials,tungsten trioxide and titanium dioxide heterojunction composites were prepared by hydrothermal method,and their chemical properties and photocatalytic properties were characterized.The main achievements are as follows:Different proportion of sulfur doped WO₃ photocatalysis materials were prepared by the secondary hydrothermal method.The micromorphology and crystal form,surface characteristics and optical properties of the materials were characterized by XRD,XPS,UV-Vis,SEM and other characterization methods.The results showed that the characteristic peaks of WS₂ appeared in XRD,indicating that the WS₂-WO₃heterojunction system was formed on the surface of the material.XPS shows that the S element replaces the O element to generate the W-S bond.The XPS high-resolution spectrum shows that the generation of O vacancies.BET shows that the specific surface area increases greatly after doping.The doping of the S element significantly reduces its band gap energy and increases the absorption of visible light.The photocatalytic performance of S-WO₃ was evaluated by measuring the photocatalytic rate of methylene blue?MB?and metoprolol?MET?under visible light.The maximum removal efficiency of MB and met of 5%S-WO₃ samples was 78.7%and28.4%,respectively.The experimental results of photocatalytic mechanism show that OH^-and O^2-are the main active materials for photocatalysis.After repeated use for three times,the removal efficiency of MB from solution of 5%S-WO₃ photocatalytic material reached85%of the initial adsorbed photocatalytic activity,maintaining a high stability.The photocatalytic materials with different ratio of tungsten trioxide to titanium dioxide were prepared by hydrothermal method with ammonium fluotitanate and sodium tungstate as titanium and tungsten sources.The materials were characterized by SEM,XRD,XPS and UV Vis.XRD results show that the composite is composed of monoclinic tungsten trioxide and anatase titanium dioxide.SEM showed that with the composite of WO₃,hollow spheres were formed in the materials,and it was speculated that the concentration of sodium tungstate as the dopant precursor played a key role in the formation of special hollow spherical structures.UV-Vis showed that the composite of tungsten trioxide decreased its bandgap energy and increased the absorption of visible light.XPS shows that W-O and Ti-O share orbital O1s in W-O-Ti link,which further indicates the generation of heterojunction.Methylene blue?MB?and metoprolol?MET?were used as the target pollutants to evaluate the photocatalytic performance of the heterojunction composite.The experimental results showed that WO₃-TiO₂ had more excellent visible photocatalytic performance.The maximum removal efficiency of MB and met of 10%WO₃-TiO₂samples reached 87.8%and 67.1%.The experimental results of photocatalytic mechanism show that OH^-and O^2-are the main active materials for photocatalysis.After repeated use for three times,the removal efficiency of MB from solution of 10%WO₃-TiO₂ photocatalytic material reached 90.8%of the initial adsorbed photocatalytic activity,maintaining a high stability.