The Preparation And Visible Light Photocatalytic Performance Of Silver Phosphate Composites

With the rapid development of the society,the problems of environmental pollution are more and more serious.Semiconductor photocatalytic technology is widely used to solve environmental pollution and energy shortage because of its simple operation,mild reaction conditions,high removal rate,low energy consumption and no pollution.As the traditional semiconductor material,TiO2 has the advantages of stable chemical property,high catalytic activity,low cost and has no harm to environment.But because of its wide band gap,Ti O2 only has the ultraviolet photocatalytic activity,namely,it can not be excited under visible light.So,TiO2 can not make full use of sunlight and has low quantum efficiency.Even though TiO2 is modified,its practical application has been still limited because of its own shortcomings.As a new photocatalytic material,Ag₃PO₄ has the advantages of narrow band gap,strong absorption to visible light,quantum efficiency of more than 90%.Then,Ag₃PO₄ is widely researched.Amining at the disadvantages of low solubility in water,photocorrosion,and its high cost,this paper mainly uses the semiconductor compound to modify Ag₃PO₄.And the main contents are as follows:（1）Bi₂WO₆,Ag₃PO₄ and Bi₂WO₆/Ag₃PO₄ were all prepared by hydrothermal method.Then,X-ray diffraction（XRD）,scanning electron microscopy（SEM）,UV-Vis diffuse reflection（UV-Vis DRS）and photoluminescence（PL）were used to study the morphology structure and optical properties.And the experiments of photocatalytic degradation of rhodamine B（RhB）were conducted under visible light.The results are as follows: the photocatalytic performance of all composite catalysts was better than that of pure Bi₂WO₆ and Ag₃PO₄.When the molar ratio n（Bi₂WO₆/Ag₃PO₄）was 0.3,the pH was 7.0,the hydrothermal time was 12 h,and the hydrothermal temperature was 180 ℃,the photocatalytic activity of Bi₂WO₆/Ag₃PO₄ was the best,and the best degradation rate was 96% in 30 min,but under the condition of same photocatalytic reaction,the degradation rates of pure Bi₂WO₆ and Ag₃PO₄ were respectively 21.3% and 24.7%.And the apparent reaction rate constant K was respectively 31 times and 40 times more than that of pure Bi₂WO₆ and Ag₃PO₄,so the reaction rate was accelerated.The degradation rate of Bi₂WO₆/Ag₃PO₄ on RhB after 4 times recycles was 83.1%,which shows that Bi₂WO₆/Ag₃PO₄ has good stability.h+ and ·O2-radical were the main active species in the photocatalytic degradation progress of Bi₂WO₆/Ag₃PO₄.UV-Vis DRS shows that the photocatalytic activity is enhanced by the broadening of the absorption range of the photocatalyst after the catalyst is composited.PL reveals that the lifetime of photo-generated electron-hole pairs is prolonged and the photocatalytic activity is greatly enhanced.（2）BiPO4,Ag₃PO₄ and BiPO4/Ag₃PO₄ were all synthesized by one-step hydrothermal method.Then,the structure and properties of the catalysts were studied by SEM,XRD,PL and UV-vis DRS.The photocatalytic activity of the catalyst was evaluated by the degradation efficiency of rhodamine B under the visible light.The results are as follows: the optimum synthesis conditions for BiPO4/Ag₃PO₄ were molar ratio（BiPO4/Ag₃PO₄）of 0.1,pH of 5.0,hydrothermal temperature of 180 ℃,hydrothermal time of 12 h,when the degradation rate was 93.1% in 20 min,which was respectively 4.7 times and 4.6 times higher than that of pure BiPO4 and Ag₃PO₄.The degradation rate of BiPO4/Ag₃PO₄ on RhB after 4 times recycles was 84.6%,which proved its stability was good.h+ and ·O2-and ·OH radicals were all involved in the photocatalytic degradation reaction of BiPO4/Ag₃PO₄ composites,in which h + and ·O2-played a main role.UV-vis DRS and PL spectra show that the semiconductor compound modification not only broadens the response range of visible light,but also promotes the separation efficiency of photo-generated electron-hole pairs,thereby its photocatalytic activity is improved.（3）With the main raw materials of silver nitrate and disodium hydrogen phosphate,a series of different Ag₃PO₄ were successfully prepared under the conditions of different hydrothermal time,hydrothermal temperature and pH by hydrothermal method.The structure and properties of the catalysts were investigated by XRD,SEM and PL.The photocatalytic activity of the catalyst was confirmed by the degradation rate of Rhodamine B（RhB）under visible light,it was found that the photocatalytic activity of the catalyst was the highest when the hydrothermal time was 12 h,the hydrothermal temperature was 180 ℃,and the pH was 7.0.