| Photocatalytic technology has unique advantages in solving energy problems and environmental pollution.Sillen-aurivillius bismuth series compounds have layered structures which can accelerate the transfer of photogenerated carriers.Bi4TaO8Cl,for example,is expected to be applied in the fields of photocatalytic decomposition of water,photocatalytic reduction of carbon dioxide,photocatalytic nitrogen fixation and degradation of organic pollutants due to its suitable valence band conduction band position and band gap,high photostability and environmental friendliness.However,at present,Bi4TaO8C1 has low photoelectron-hole separation efficiency and is easy to recombine,which greatly limits its quantum efficiency.Therefore,doping modification of Bi4TaO8Cl is an important means to improve its photocatalytic performance.In this paper,modification is carried out through the construction of solid solution and the loading of precious metal.The main contents are as follows:Bi4TaO8ClxBr1-x solid solutions with different proportions were prepared by solid phase method and molten salt method.The physical and chemical properties of the solid solution were characterized by XRD,SEM,BET,DRS,Mapping,PL spectrum and EDS.The photocatalytic performance of the prepared solid solution was evaluated by photocatalytic degradation of Rhodamine B（RhB）under 300W xenon lamp irradiation.When Br:CI=1:3,the samples with the highest activity can be obtained.Through DRS analysis,we found that the construction of a series of solid solutions can change the size of the energy gap and affect the photocatalytic activity.PL spectrum analysis shows that the construction of solid solution can effectively improve the transfer rate of photoborne carriers and inhibit the hole-electron recombination.The results of free radical capture experiments showed that hole（H+）and superoxide radical（·O2-）were the main active species for photocatalytic degradation of rhodamine B.In addition,the solid solution catalyst has good photocatalytic stability after three cycles of degradation of RhB.The Bi4TaO8Cl sample prepared by molten salt method was compared with the solid phase,and it was found that the sample with improved method had a more regular morphology.The calcination of solid phase changed from block to flake,which reduced particle size and increased specific surface area.The smaller size and larger specific surface area provide more active sites and improve quantum efficiency.Bi4TaxNb1-xO8Cl solid solutions with different proportions were prepared by solid phase method and molten salt method.The physical and chemical properties of the solid solution were characterized by XRD,SEM,BET,DRS,Mapping,PL spectrum and EDS.The specific surface area of the sample prepared by molten salt method is about twice that of the solid method,and the specific surface area of the solid solution is close to that of the pure one.Bi4NbOsCl pure phase samples prepared by the melt salt method have achieved excellent results in the photocatalytic degradation of Rhodamine B,because of its narrower band gap and wider light absorption,while Bi4TaO8Cl pure phase samples prepared by the solid phase method have higher reactivity in the.photocatalytic degradation of Rhodamine B.Based on Bi4TaO8Cl samples prepared by molten salt method,we carried out photodeposition of different precious metals in different proportions.A series of samples were characterized by XRJD,SEM,TEM,XPS and DRS.From the SEM spectrum,we observed that Pt particles existed on the surface of the sample in the form of simple substance,and the distribution was relatively uniform.The lattice of Pt was found in TEM,and the XPS characterization showed 4f characteristic peak of Pt.This confirms the way Pt exists.Fluorescence analysis showed that Pt loading was beneficial to carrier separation efficiency.DRS analysis shows that Pt load causes the wavelength of light absorption to be redshifted,the range of light absorption is enlarged,and the utilization rate of light energy is improved.Through the degradation of tetracycline,a typical antibiotic,we found that the addition of Pt greatly improved the degradation rate.The degradation time of blank sample was 20min,and the degradation time was about 80%,while the sample loaded with precious metal only needed 5min to degrade thehigh concentration of tetracycline about 80%,which greatly improved the degradation efficiency.In addition,the catalyst was recycled and reused,and three stability tests were conducted to find that the performance of the sample had no significant attenuation.The optimal proportion of Nb5+and Br-double doped solid solution was synthesized by solid phase method,and the same amount of different precious metals（Au,Ag,Pt）were loaded by photodeposition method.The photocatalytic activity of Nb5+ and Br-double doped solid solution was conpared and its properties were characterized.Experiments show that the Au-loaded solid solution has the best performance,which depends on the high electron-hole efficiency and the improvement of light absorption capacity. |
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