Preparation And Photocatalytic Properties Of Composite PbWO 4 Nm Photocatalyst

As a kind of efficient method for removing organic pollutants,semiconductor photocatalytic technology has broad application prospect in the field of environmental protection.PbWO₄ is a typical tungsten-based semiconductor with relatively stable structure.It has many advantages such as simplicity in preparation,stable photochemical properties,high density and easy to separate and recycle.However,as a photocatalyst,it is confronted with some problems,e.g.narrow photoresponse range,recombination rate of photogenrated electrons and holes.In order to improve the photocatalytic activity of PbWO₄,the effects of different hydrothermal temperatures and different hydrothermal times on the structure and photocatalytic activity of PbWO₄ were studied.Then on the basis of optimal reaction conditions and with the aim to degrade dyes,the effects of noble metal loading,non-metallic element modification,and metal compound compounding on the structure and photocatalytic performance of PbWO₄ were further investigated.The main research contents are as followings:Firstly,a series of?Ag,Pt?/PbWO₄ nanorod photocatalysts were synthesized by hydrothermal-photoreduction method.Firstly,the effect of different hydrothermal temperature and time on the photocatalytic performance of PbWO₄ was investigated using CTAB as a template,and then the influence of different loadings of Ag,Pt on the performance of the catalyst was investigated.The results show that PbWO₄ has the best activity when the hydrothermal temperature is 160°C and hydrothermal time is 18 h.Then Ag,Pt nanoparticles were loaded on PbWO₄ fabricated under optimum hydrothermal conditions.The electrons can be transferred from the conduction band of PbWO₄ to Ag,Pt due to the surface plasmon resonance effect of Ag,Pt,so that the separation rate of electrons and holes can be improved.Experimental results showed that when the loading contents of Ag,Pt are 0.5%and 1%,the obtained?Ag,Pt?/PbWO₄ has the best photocatalytic activity and stability.Secondly,PbWO₄ dendritic microcrystalline photocatalyst modified by different content of non-metallic C was prepared by a simple hydrothermal method.The results of characterization analysis show that non-metallic C can act as electron capture centers,to accelerate the separation of electrons and holes and improve the utilization of carriers,and increase the absorption of PbWO₄ in the visible region in a certain extent,.The photocatalytic degradation of many kinds of organic contaminants had been investigated to test photocatalytic activity.The results showed that when the content of C is 0.52%,C/PbWO₄exhibits the highest activity.Thirdly,the Bi₂WO₆/PbWO₄ dendritic photocatalyst was prepared by two-step hydrothermal method.The experimental results show that the composite Bi₂WO₆ possesses high specific surface area.When loading concent of Bi₂WO₆ is 15%,Bi₂WO₆/PbWO₄exhibits the best photocatalytic degradation activity.The Bi₂WO₆ compsite has the two interfaces,which is conducive to the transfer of photogenerated carriers.The high separation rate of photogenerated electrons and holes,and the increase of the specific surface area are conducive to the full contact between the catalyst and the contaminants.Therefor the photocatalytic activity of the PbWO₄ can be improved.The above studies indicated that choosing suitable hydrothermal synthesis conditions and using appropriate noble metal,non-metallic modification and metal oxide composites can improve the surface properties of PbWO₄ catalysts,regulate the crystal surface structure,and accelerate the separation efficiency of photogenerated electrons and holes.Thereby,the degradation performance of PbWO₄ photocatalyst for organic pollutants can be effectively increase.