Construction Of Bismuth Oxycarbonate Heterojunction And Its Degradation Of Toluene

As a kind of poisonous and harmful gas,volatile organic gases?VOCs?are not only easy to cause serious environmental pollution,but also easy to cause irreversible damage to human health.Toluene,as the most representative organic pollutant,will not only damage the respiratory system of human body,but also affect the nervous system of human body and cause irreversible damage.Among many methods of toluene treatment,photocatalytic technology has attracted more and more attention because of its low energy consumption,simple operation,good removal effect and no secondary pollution.Because of its unique layered structure,Bi2O2CO3 materials are easy to control the morphology and inhibit the recombination of photogenerated electrons and holes to a certain extent,and its huge application prospect has become a research hotspot.In the application of photocatalysis technology in the actual treatment of toluene gas,we should focus on the following aspects:try to improve the specific surface area of Bi₂O₂CO₃;use appropriate methods to reduce the band gap of Bi₂O₂CO₃ material;further reduce the complex situation of photogenerated electrons and holes.In this paper,the problems in the treatment of toluene with Bi₂O₂CO₃ are studied as follows:?1?Preparation of flake Bi₂O₂CO₃ and 3D Flower Bi₂O₂CO₃ and test of their biodegradability to toluene gas.The 2D flake Bi₂O₂CO₃ and 3D Flower Bi₂O₂CO₃ were prepared by hydrothermal method.The morphology and light absorption characteristics of the materials were determined by XRD,SEM,UV-Vis and other characterization methods.The toluene degradation energy of the materials was tested under xenon lamp,and the difference of the toluene degradation performance of Bi₂O₂CO₃ materials with different morphology was analyzed.?2?The construction of flower like Bi₂O₂CO₃-CdS-CuS stable inhibition junction and its degradation of toluene gas.First of all,the Bi₂O₂CO₃ flower decorated with sheet structure was made.Bi₂O₂CO₃ flowers are closely decorated with lamellar structure to provide a larger specific surface area,which can be contacted with toluene.Finally,Bi2O2CO3 and CdS-CuS were prepared by one-step hydrothermal method to form ternary heterojunction.The increase of activity is due to the fact that more active substance·OH can be produced by the ternary heterojunction to degrade toluene.The 3p orbital of sulfur atom in CuS can be used as electron acceptor to improve the stability of surface sulfur vacancy.In addition,the existence of CuS can solve the problem of deactivation caused by CdS photoetching under light conditions.The valence change of S element in CuS-CdS-BOC is only 1.1%,and the valence of S element in CdS-BOC before and after reaction is as high as 7.5%.The degradation rate of toluene can reach 67%at 3000 ppm.In addition,the band gap of the composite decreased from 3.2eV to 2.25ev.A new alternative catalytic material for toluene degradation is provided.Through this work,reliable strategies are provided to enhance the stability of S in CdS.?3?The construction of Z-type flower CdS-CQDs-Bi2O2CO3 inhibition junction and its degradation of toluene gas.The flower like Bi₂O₂CO₃ was synthesized by hydrothermal method.The degradation of toluene was used as photocatalyst.Flower like Bi2O2CO3 is more favorable to absorb visible light and contact with toluene.Then,the Z-type CdS-CQDs-Bi₂O₂CO₃ heterojunction formed by Bi₂O₂CO₃,CdS and CQDs was prepared by immersion and agitation to enhance the degradation of gaseous toluene.The increase in activity is attributed to the retention of the high redox capacity of·O₂^2-and·OH in the Z-scheme heterojunction.Compared with pure Bi₂O₂CO₃,the degradation of toluene at 3000 ppm may be reduced from 20%to 47%.At the same time,TEM and XPS show that there is ternary heterojunction.Through the photoelectric conversion and UV,we can see that Z-type composite has excellent photoelectric conversion efficiency and light absorption effect.The band gap of the composite is reduced from 3.2eV to 2.75ev,and the transient photocurrent and impedance of the composite are better than those of other monomer materials,which shows that the existence of Z-type heterojunction improves the efficiency of photogenerated electron hole migration and prolongs the life of electron and hole.Finally,the valence band potentials of Bi₂O₂CO₃ and CdS were measured by XPS,and the charge transfer mechanism of Z-scheme CdS-CQDs-Bi₂O₂CO₃ was verified.