Preparation And Photocatalytic Properties Of Tungsten Trioxide And Its Composites

In the past decades,water pollution by different kinds of dyes and heavy metals from factories are proposing a crucial worldwide environmental emergency.Photocatalytic,one of the most effective methods to handle the crisis of water pollution,has received extensive attention in recent years.As a typical photocatalyst,TiO₂ has been extensively studied.However,the wide energy band gap restricts its applications under visible-light.Seeking new photocatalysts with suitable band gaps and chemical stability has been a hot issue in recent decades.As a semiconductor oxide,tungsten trioxide?WO₃?with a band gap of 2.8 eV has unique optical properties.Besides,tungsten trioxide has high chemical and thermal stability at room temperature.Two strategies have been adopted to improve the efficiency of photocatalytic.For one hand,the loss of the combination of electron and hole on the materials surface can be reduced by regulating the morphology and increasing the specific surface area of the material.For another,the electric potential existing between the two semiconductors form a built-in electric field at the interface of two semiconductors,which promotes the effective separation of the electrons and holes.WO₃ with different morphologies and tungsten trioxide/silver oxide composites were synthesized by hydrothermal method,and their morphology and properties were analyzed by a variety of characterization methods.The main results are given as follows:?1?WO₃ nanorods photocatalyst has been synthesized via a hydrothermal method for photocatalytic degradation of methylene blue.Results showed that WO₃ nanorods possessed a one-dimensional,hexagonal structure with the average length and diameter of 5?m and 200 nm,respectively.UV-Vis spectrophotometry showed that the sample had absorbance in the range of visible light.Results showed that the efficiency of photocatalytic degradation of methylene blue was about 34%in 60 minutes under visible light.?2?Several WO₃ nanostructure with different morphology have been synthesized via hydrothermal method.The morphology of the material has been controlled by adding some template agents or surfactants.WO₃ nanoparticles,nanorod bundles,nanotube array and nanorods have been synthesized in this work.The results showed that the photocatalytic performance of structures with large surface area is obviously better than that the ones with smaller surface area.It is realized that the specific surface area of the material has a certain effect on its photocatalytic activity.?3?A one-dimensional complexes of tungstun trioxide and silver oxide?WO₃/Ag₂O?has been synthesized via hydrothermal method.Ag₂O attached to WO₃ nanorods formed hexagonal nanoparticles and the average diameter reached 20 nm.Compared to single component,the composite structure had larger specific surface area and more active sites,which comtributed to the improvement of photocatalytic performance.The synergistic effect of WO₃ and Ag₂O played a vital role in the enhanced photocatalytic performance.The combination of tungsten trioxide and silver oxide has changed the band gap of the photocatalyst whereas the photocatalytic efficiency of the composites reached 98%in 60 minutes under visible light.