Research Of Preparation And Photocatalytic Performance Of Magnetic Bismuth-based Composite Materials

With the rapid development of industry and the significant increase of population,serious environmental pollution has occurred.Improving green sustainable technologies to ensure sustainable development is a top priority.As a renewable energy-driven technology,semiconductor photocatalysis（PC）has attracted the attention of researchers in the degradation of pollutants.Wide-bandgap semiconductors can only absorb a small amount of ultraviolet light in sunlight,which greatly affects the catalytic activity of photocatalytic materials.Among various semiconductors,especially bismuth-based materials,have attracted continued attention due to their excellent visible light absorption,suitable band gap,and considerable chemical stability.In order to find low-cost,high-performance and recyclable photocatalysts,three magnetic bismuth-based composites were designed and prepared and the photocatalytic properties of the composites were investigated by degrading organic dyes.The specific research contents are as follows:（1）A one-dimensional（1D）magnetic recyclable Bi₂Fe₄O₉/C@Ag Br composite photocatalyst was prepared by combining electrospinning technology and precipitation-deposition method.A heterojunction was constructed between Bi₂Fe₄O₉,C and Ag Br to improve the catalytic performance.The 1D Bi₂Fe₄O₉ fibers can provide magnetic properties,and can transfer photogenerated carriers to the reaction center effectively,solving the problem of the spatial localization of carriers.Morphological and compositional characterization of the composites by scanning electron microscopy（SEM）,X-ray diffractometer（XRD）,X-ray photoelectron spectroscopy（XPS）,surface area and pore size analyzer（BET）and vibrating sample magnetometer（VSM）.The photocatalytic activity of the photocatalyst was investigated by degrading methylene blue（MB）under simulated illumination,and the mechanism for the enhanced photocatalytic activity were verified by photospectroscopy（PL）and radical trapping tests.The results showed that the efficiency of Bi₂Fe₄O₉/C@Ag Br was 97.4%under simulated illumination for 60 min.After three cycles,the catalytic efficiency still kept at 88%,revealing that Bi₂Fe₄O₉/C@Ag Br has good stability.（2）Co₃O₄ nanosheets were coated on the surface of hollow Fe₃O₄@SiO₂microspheres by oil bath method,and a heterojunction with BiOCl was constructed on the Co₃O₄nanosheets to improve the catalytic performance.The formed three-dimensional（3D）flower-like Fe₃O₄@SiO₂@Co₃O₄@BiOCl composite photocatalyst consists of a magnetic core and a flower-like shell.The morphology and composition of composites were characterized by SEM,XRD,Fourier transform infrared（FTIR）,XPS,BET and VSM.Under simulated illumination,the photocatalytic activity of photocatalyst was investigated by degrading rhodamine B（Rh B）and the degradation efficiency reached 98.41%within 50 min.The mechanism for enhanced photocatalytic activity was verified by PL and radical trapping tests.（3）1D magnetic flower-like Co Fe₂O₄@Bi₂WO₆@BiOBr composite photocatalysts were synthesized by a solvothermal method combined with electrospinning and precipitation-deposition methods.A heterojunction between BiOBr and flower-like Bi₂WO₆ was constructed to improve the catalytic performance.Magnetic Co Fe₂O₄ fibers are convenient for magnetic separation and recovery and can also solve the problem of carrier spatial localization.The morphology and composition of the composites were characterized by SEM,XRD,FTIR,XPS,BET and VSM.Under simulated illumination,the catalytic activity of photocatalyst was investigated by degrading Rh B and the degradation efficiency reached 92.08%within 180 min.The mechanism for enhanced photocatalytic efficiency was verified by PL and radical trapping tests.In this paper,three preparation schemes for magnetic bismuth-based composite photocatalysts had been reported,which provide new ideas for the preparation of bismuth-based semiconductor composite photocatalysts.