Preparation And Photocatalytic Performances Of One Dimensional Bismuth Based Composite Materials

With the rapid development of industrialization and urbanization,the problems of environmental pollution and energy shortage have been become increasingly prominent and intractable.In order to solve these problems,various measures have been implemented.Among them,photocatalytic technology has been widely concerned and researched because of its high efficiency,low cost,environmental friendly and mild reaction conditions.As a kind of bismuth oxyhalide(BiOX),BiOI has special layered structure and great visible light response ability.However,photogenerated electrons and holes are easy to combine due to its narrow band gap,which limits the photocatalytic performance of BiOI.Meanwhile,traditional powder catalyst are easy to lose and hard to recycle in the reaction process.In view of these shortcomings,this paper constructed heterojunction between BiOI and Bi₂O₃,BiOCl,BiVO₄to reduce the recombination rate of photogenerated electrons and holes.Meanwhile,one-dimensional polymer fiber was used as the carrier to overcome the shortcomings of easy loss of powder catalyst.The photocatalytic performance of the composite material was evaluated by degradation of organic pollutants and the possible photocatalytic mechanism was proposed.(1)The Bi₂O₃hollow tube was prepared via electrospinning,solvothermal and high temperature calcination method.Then,the Bi₂O₃/BiOI composite catalyst was prepared by ion exchange in KI aqueous solution.The SEM result showed that the Bi₂O₃/BiOI composite catalyst was tubular and the nanosheets were cross loaded on the surface of the hollow tube.The formation of Bi₂O₃/BiOI heterojunction was analysed by XRD and XPS.The results of PL spectra,transient photocurrent and impedance showed that the formation of the composite catalyst can improve the transfer and separation efficiency of photogenerated electrons and holes.Bi₂O₃/BiOI composite catalyst has great degradation performance of tetracycline hydrochloride(TC).The degradation efficiency of composite catalyst BB-4 for TC reached 85%under visible light irradiation for 2 h.In the fourth degradation,the degradation efficiency was about 75%.In addition,the composite catalyst has great degradation activity for other antibiotic pollutants.The capture experiment showed that the main active components of TC degradation were·O₂^-and h⁺,and the corresponding Z-type heterojunction photocatalytic mechanism was proposed.(2)BiOCl-BiOI/PAN NFs was prepared by electrospinning and one pot solvothermal method.One dimensional polymer fiber was used as carrier,and the nanosheets were uniformly and compactly loaded on the surface of the fiber.The photocatalytic activity of the composite catalyst was evaluated by the degradation of rhodamine B(Rh B)and tetracycline hydrochloride(TC).The degradation efficiency of composite catalyst ICl-31 for Rh B was 98.7%under 1 h visible light irradiation and 82.1%for TC under 2 h visible light irradiation.In the fourth degradation,the removal efficiency of Rh B and TC remained at 94.5%and 78.5%,respectively.The morphology and crystal structure of catalysts did not change significantly,indicating that the catalysts have great stability.The capture experiments showed that the main active component are·O₂^-,which suggested a possible direct Z-heterojunction photocatalytic mechanism.(3)Firstly,BiOI/PAN NFs was prepared by electrospinning and solvothermal method.Then,V(acac)₂was added into the system for secondary solvothermal treatment,and ion exchange was carried out to prepared BiVO₄-BiOI/PAN NF_Scomposite catalyst.Flower like microspheres grew uniformly on PAN fibers.The photocatalytic performance of the composite was investigated by the degradation of TC under visible light irradiation.The photocatalytic degradation performance of the composite was significantly better than that of BiOI/PAN NFs and BiVO₄.In addition,Rh B,rhlortetracycline hydrochloride(CC),bisphenol A(BPA)and phenol were also degraded,indicating that the composite catalyst has certain universality.The capture experiment showed that the main active components were·O₂^-and·OH,and the corresponding Z-type heterojunction photocatalytic mechanism was proposed.Due to the existence of polymer fiber support,the composite catalyst has great stability and was easy to be recycled from the reaction system.In conclusion,the heterojunction constructed by combining Bi₂O₃,BiOCl and BiVO₄with BiOI can significantly improve the separation efficiency of photogenerated electrons and holes,and further enhance the photocatalytic performance.Due to the existence of polymer fiber,the cycle stability of the composite catalyst was improved and easy to separate and recover from the reaction system,which plays a greater advantage in practical application.