Modification Of BiOCl-based Photocatalysts And The Enhancement Mechanism Of Their Photocatalytic Activity

Due to its good photoelectric properties,strong oxidation ability,low toxicity and low cost,bismuth oxyhalide BiOX has become a semiconductor material with great potential in the field of photocatalysis.Therefore,the development of new photocatalysts based on BiOX has become the focus of research.However,there are still many shortcomings,such as high recombination rate,slow migration rate of photogenerated electron-hole pair and low visible-light adsorbed ability,which limit the photocatalytic applications of BiOX catalyst.In order to improve the photocatalytic performance of BiOX,in this work,three strategies have been employed,which include adjusting different solvents,formation a binary heterojunction and loading the metallic Ag nanoparticles.The specific research contents are as follows:1.BiOCl has been synthesized by a simple solvothermal method using different alcoholsas solvents.It was found that compared to BiOCl prepared using other alcohol,BOC-M prepared with methanol exhibits the highest photocatalytic activity for degrading rhodamine B aqueous solution.The photocatalytic degradation rate constant of BOC-M was 7.48 h^-1.After 40 visble-light irradiation,Rh B?25.0 mg/L?is almost degraded completely.The enhancement mechanism of catalysts is attributed to the enhancement of the light absorption ability and charge transfer resistance,which causes the photogenerated electron-hole pairs efficient separation.2.BiOCl/BiOI photocatalyst was synthesized by one-step solvothermal method with mannitol as solvent and PVP as surfactant.Experimental results showed that compared with naked BiOCl and BiOI,BiOCl/BiOI heterojunction present greatly improved photocatalytic activity for degrading of rhodamine B,methyl orange and ciprofloxacin.Among them,BiOCl/BiOI-2 catalyst synthesized under the optimized conditions has a rate constant of 8.02 h^-1,4.08 h^-1,and 0.81 h^-1,for degradation of of Rh B,MO,and CIP,respectively.These results indicate that the BiOCl/BiOI photocatalyst on the photocatalytic degradation of dyes and antibiotics has a broad spectrum.The enhancement mechanism is attributed to the formation of a binary heterojunction,which is helpful to promote the effective separation of photo-generated electron-hole pairs and increase the transport rate of photo-generated carriers.3.Ag-BiOCl/BiOI-2 photocatalyst was synthesized by two-step solvothermal method,in which metal Ag nanoparticles were loaded onto BiOCl/BiOI-2 by light reduction method.Photocatalytic performance was investigated by degrading rhodamine B,methyl orange and other dyes and ciprofloxacin aqueous soluiton.Experimental results showed that the photocatalytic activity of BiOCl/BiOI-2 has been effectively improved by the introduction of metals into the system.Among them,6%Ag-BiOCl/BiOI-2 has the highest photocatalytic activity.It also reflects that Ag-BiOCl/BiOI-2 photocatalytic system has broad spectrum,which is suitable for the degradation of different organic pollutants.This is mainly because the formation of a multi-element heterojunction,which is helpful to inhibit photo-generated electron-hole pair recombination,and the surface plasmon resonance effect of metal Ag is contributed to enhance the light absorption capacity.