Preparation And Photocatalytic Performance Of WO₃ And Its Composite Semiconductor Photocatalyst

Tungsten oxide（WO₃）is an important n-type semiconductor.WO₃has a large band gap range（2.5 to 2.8 e V）.WO₃has great potential in photocatalysts.Its superior physical properties and chemical properties have caused people Great research interest.Due to its high crystallinity,high stability,large specific surface area and narrow band gap,Nano WO3 has been widely used in many fields such as photocatalysis,gas sensors,electroluminescent devices,supercapacitors,etc.However,at present,the energy of sunlight cannot be fully utilized,and photo-generated electron-hole pairs are easy to recombine,resulting in low photoelectric conversion efficiency and poor photocatalytic performance.This paper proposes a new idea:firstly prepare different crystal forms of WO₃,improve its morphology and photocatalytic performance by changing experimental parameters,and then through material recombination to form pn-type CaFe₂O₄/WO₃and nn-type WO₃/ZnO heterogeneous Junction of composite semiconductor materials improves the efficiency of photo-generated electron-hole pair separation and improves the photocatalytic performance of WO₃.The details are as follows:1)Using sodium tungstate as the tungsten source,three crystal forms of WO₃nanoparticles were prepared by a simple one-step hydrothermal method.The experimental parameters such as the type of surfactant,the concentration of oxalic acid,the type of acid,and the heat treatment temperature were changed.To investigate the effect on the phase structure,sample morphology,and photocatalytic performance of WO₃with different crystal phases,The results showed that the concentration of methylene blue solution did not decrease in the absence of catalyst in 210 minutes.When photocatalyst WO₃was added to methylene blue solution,the degradation rate of MB by orthogonal phase WO₃（O-WO₃）was about 90%.The degradation rate of MB by hexagonal phase（h-WO₃）is about 75%,and the degradation rate of MB by monoclinic phase（m-WO₃）is about 73%.In comparison,orthogonal phase WO₃shows Hexagonal and monoclinic phases have better photocatalytic activity2)The p-CaFe₂O₄/n-WO₃type heterojunction composite semiconductor material was prepared by a combination of hydrothermal method and heat treatment.The results show that the p-CaFe₂O₄/n-WO₃composite semiconductor material has more properties than pure n-WO₃.The large specific surface area and pore diameter allow the catalyst to absorb more photon energy and have more active sites to improve the photocatalytic activity of the catalyst.The experiment found that compared with CaFe₂O₄or WO₃with a single component,the doping amount of CaFe₂O₄has a very significant effect on the photocatalytic activity.Among them,5%of WO₃/CaFe₂O₄showed excellent photocatalytic performance,and the methylene blue was degraded in simulated visible light.In the experiment,the degradation rate reached 90%in 6 hours;At the same time,the activity of the C-W-5%photocatalyst was tested.After repeated use three times,the photocatalytic degradation rate was still above 86%.3)A WO₃/ZnO composite with microspheres using carbon spheres as a template,zinc acetate as the zinc source,and sodium tungstate as the tungsten source.The results show that when carbon spheres are added as a support,the photocatalytic performance of the composite photocatalyst can be enhanced to a certain extent.;When exploring the effect of solution p H on the morphology and photocatalytic performance of WO₃/ZnO composite semiconductor materials,where the solution p H=6,the degradation rate is slightly higher than the degradation rate of methylene blue under acidic and alkaline conditions;When investigating the effect of different molar ratios of zinc and tungsten on the morphology and photocatalytic performance of WO₃/ZnO composite photocatalyst,the composite photocatalyst Zn:W=8:1has the highest photodegradation activity,showing that it is better than the single component WO₃,Better photocatalytic performance of ZnO.And in the case of ultraviolet light irradiation,10 mg/L MB was completely degraded within 60 min.Use it to degrade methylene blue three times in a row,and it can also completely degrade photocatalytically.This shows that the Zn:W=8:1 composite photocatalyst has good photocatalytic stability and recyclability.