In Situ Synthesis And Photocatalytic Activity Of Bi₂O₂CO₃ And Its Heterojunctions

The problem of environmental pollution caused by the rising level of global industrialization is becoming increasingly serious,of which water pollution is extremely prominent.Although there are many physical adsorption methods,membrane separation,biodegradation methods and chemical oxidation methods,these traditional methods still have the possibility of secondary pollution to the environment.Therefore,it is urgent to find a pollution-free and cheap treatment method.As a new sewage treatment method,photocatalytic technology has the characteristics of environmental friendliness and no secondary pollution.It is widely used.A large number of researchers are devoted to research and develope the application of semiconductor photocatalysts in the degradation of organic matter,hoping to use the excellent performance of semiconductor photocatalysts to solve existing environmental pollution problems.Bismuth oxycarbonate?Bi₂O₂CO₃?is a layered oxide with a special Aurvillius/Sillén structure,so it has become a research hotspot.But Bi₂O₂CO₃ has a wider band gap,which limits its application in photocatalysis.In this paper,a new type of ionic liquid-assisted solvothermal method was used to prepare Cl-doped bismuth oxycarbonate?Bi₂O₂CO₃?photocatalyst.Ionic liquid of[Hnmp]Cl not only enhanced the solvothermal process and promoted the formation of Bi₂O₂CO₃,but also provided chloride element as dopant.The photocatalytic activity of the catalyst was studied by degrading RhB under full light irradiation.Nanomaterials were characterized by x-ray diffraction?XRD?,x-ray photoelectron spectroscopy?XPS?,cold field emission transmission electron microscope?TEM?,scanning electron microscope?SEM?,electron spin resonance spectrometer?ESR?and other means.The results show that the doping of Cl element induces the formation of oxygen vacancies,increases the absorption of visible light,and improves the separation efficiency of photo-generated electrons?e^-?and hole pairs?h⁺?,and thus improves its photocatalytic RhB under full light active.Further investigation reveal that the heterojunction nanomaterials with adjustable?-Bi₂O₃/Bi₂O₂CO₃ ratio can be synthesized by adjusting the calcination temperature and calcination time.The photocatalytic activity of?-Bi₂O₃/Bi₂O₂CO₃ heterojunction under visible light irradiation is improved,however,under ultraviolet irradiation,the heterojunction activity is lower than Bi₂O₂CO₃.The photocatalyst was characterized by DRS,Mott-Schottky experiment,Kelvin probe,SPV,ESR,photocurrent,etc.The results show that when the heterojunction formation of?-Bi₂O₃ and Bi₂O₂CO₃,the valence band position of Bi₂O₂CO₃ rises and the holes at VB of Bi₂O₂CO₃?at potential of 2.34 V?will migrate to the VB of?-Bi₂O₃?at potential of 1.38 V?,which remarkablely decreases the oxidative ability of holes.The negative effect of the hole's oxidizing ability on photocatalytic activity exceeds the improved efficiency of photo-generated carrier separation has a positive effect on activity.Therefore,the photocatalytic activity of?-Bi₂O₃/Bi₂O₂CO₃ under UV light is not as good as that of Bi₂O₂CO₃.