Synthesis And Photocatalytic Degradation Performance Of Bismuth Oxyhalide Composite Photocatalytic Materials

Bismuth oxyhydroxide BiOX?X=Cl,Br,I?is sandwiched between two halogen ions by a[Bi₂O₂]²⁺layer to form a?[X-Bi-O-Bi-X]?layered structure.It is a very important photocatalytic material.Among them,BiOBr has a narrow gap width of about 2.7 eV,and has a wide range of light absorption including visible light.In addition,BiOBr has good chemical stability.HoweVer,for bare BiOBr,Its photogenerated electron-hole pairs are easy to recombine,so its practical application is limited.BiOCl has a gap width of 3.46 eV and can only absorb ultraviolet light in sunlight.The composite photocatalytic material prepared by the bismuth oxyhalide composite electronic structure matching semiconductor can increase the absorption range of the solar spectrum,and effectively separate the electrons and holes,thereby improving the catalytic activity in visible light.Using Bi?NO₃?₃·5H₂O as a source in the text,BiOBr and BiOCl 2D nanosheets were prepared by one-step hydrothermal method,and different composite photocatalysts were prepared with N-SrTiO₃ and Bi₂O₂?OH??NO₃?,respectively.We analyzed The structure,morphology and optical properties of the prepared samples by SEM,XRD,XPS,UV diffuse reflectance spectroscopy,fluorescence spectroscopy and photocurrent.The photocatalytic performance of the sample was investigated by using 300W xenon lamp as visible light source and RhB as the simulated pollutant.???The obtained BiOBr prepared by using different solvents exhibited different photocatalytic properties under visible light.BiOBr prepared using ethylene glycol as a solvent exhibits better crystallinity.In the degradation experiment of RhB under visible light,BiOBr?ethylene glycol as solvent?showed better photodegradation performance,and the degradation rate reached 64%at 20 min,which was much higher than that of BiOBr?water as solvent??15%?.It is shown that the electron-hole recombination rate in the BiOBr nanosheet prepared by using ethylene glycol as a solvent is effectively suppressed,and the photocatalytic activity is remarkably improved.???The pure N-SrTiO₃ and BiOBr have lower degradation rate and slow degradation of RhB during photoreaction.HoweVer,the composite catalyst has improved degradation rate of RhB solution under visible light.Among them,18%N-SrTiO₃/BiOBr can degrade 100%within 60 min.The structure analysis of the composite catalyst electron band confirmed that a type II heterojunction was formed at the interface between N-SrTiO₃ and BiOBr,Which reduced the recombination rate of electrons and holes.The mechanism of the prepared N-SrTiO₃/BiOBr catalyst was investigated,Which showed that the main active species in the degradation of RhB solution were·OH,h⁺and·O₂^-.???The concentration of RhB solution in Bi₂O₂?OH??NO₃?is only reduced by18%after 100 min photoreaction,and BiOCl was degraded about 68%after 100 min.The photocatalytic activity of composite catalyst exhibited higher than bare Bi₂O₂?OH??NO₃?and BiOCl.Among them,9%Bi₂O₂?OH??NO₃?/BiOCl can completely degrade RhB after 100 min photoreaction.The combination of Bi₂O₂?OH??NO₃?and BiOCl can accelerate the transport rate of photogenerate carriers in the semiconductor and reduce the recombination rate of electrons and holes,thereby improving its catalytic activity.Studies on the photocatalytic mechanism confirmed that h⁺and·O₂^-are the main active species in the photodegradation of RhB.