Preparation,Modification And Applicaton Of Multiple Strutures Of Copper Borates

As environmental pollution becomes more and more serious,photocatalytic and gas sensing technology have been widely used in the decomposition of organic pollutants and the effective detection of harmful gases.In order to solve the problem of low utilization ratio of solar light and high working temperature of traditional gas sensing materials,the development and utilization of new type of visible light responding semiconductor materials is of great significance.Copper borates as new semiconductor materials with multiple structures,have midgap between conduction band and valence band and have no doping and crystal defects,which are expected to be applied in photocatalytic and gas sensing field.In this paper,the preparation of different structures of copper borates?Cu₃B₂O₆,CuB₂O₄,Cu?BO₂?₂?and their application in the fields of photocatalysis and gas sensing were studied.Finally,the Cu₃B₂O₆ was selected,and the modification was studied,and the mechanism of photocatalysis and gas sensing were also discussed.The main contents are as follows:1.Single-crystalline Cu₃B₂O₆ and CuB₂O₄ were prepared by sol-gel method,and Cu?BO₂?₂ was prepared by co-precipitation method.The photodegradation of methylene blue?MB?solution was used to evaluate the photocatalytic activity of different catalysts under visible light irradiation?420 nm < ? < 780 nm?.The results indicated that the photocatalytic activities of CuB₂O₄,Cu?BO₂?₂,and Cu₃B₂O₆ reached 58.5 %,71.7 % and 98.9 % respectively in MB aqueous solution(50 mg?L^-1)containing 1 g?L^-1 catalyst under visible-light irradiation for 6 h.UV-Vis DRS analysis indicated that electron transitions can occur in both the midgap state and forbidden band for Cu₃B₂O₆,this is the reason why Cu₃B₂O₆ has higher visible-light photocatalytic activity than Cu?BO₂?₂ and CuB₂O₄.By modifying the CdS and Cu₃B₂O₆ composite and adding proper amount of hydrogen peroxide,the transport and separation of the electron hole pair is promoted,which effectively inhibits the recombination of electron hole pair in the composite.The visible light catalytic properties of copper borate were further improved.2.Cu₃B₂O₆/CuBO₂/rGO composite was synthesized from graphene oxide?GO?and Cu₃B₂O₆ by hydrothermal reduction method.The gas sensing property of NO₂ at room temperature was studied and the results showed that the gas response of Cu₃B₂O₆/CuBO₂/rGO to 15 ppm of NO₂ is 21 % under visible light irradiation.The conductivity of the copper borate was greatly improved by the composite modification of graphene,while the electron transport properties of the material were enhanced.The heterostructure was formed between Cu₃B₂O₆ and CuBO₂,which effectively inhibits the recombination of electron hole pair in the composite and enhanced the sensitivity of the gas sensor in room temperature.3.The precursor was prepared from copper acetate,borax and three block copolymer P123 as template by hydrothermal method,different structure mesoporous copper borates?Cu₃B₂O₆/CuB₂O₄?were obtained through different temperature of heat treatment to the precursor.A series of samples were characterized by using X-ray diffraction?XRD?,scanning electron microscope?SEM?and N₂ adsorption-desorption isotherms and so on.The effects of temperature on the pore structure and crystal structure were investigated.