| After fruit and vegetable picking,physiological and chemical spoilage is easy to occur during storage,storage and storage.The accumulation of ethylene in plant ripeners is the main reason for its decay and deterioration.Exploring efficient new technologies for fruit and vegetable preservation has always been a hot topic of research.Regulating the ethylene content in the storage and transportation environment of fruits and vegetables is a key issue to be solved urgently in the field of storage and preservation of fruits and vegetables.Semiconductors have attracted much attention for their unique photocatalytic properties,providing an effective way to completely remove or convert ethylene into a harmless form in the storage environment of fruits and vegetables.The core of the development of new technologies for photocatalytic decomposition of ethylene preservation is to design high-performance visible light-responsive photocatalysts.In this paper,the Ti O2 and Bi2WO6 semiconductors,which are favored in the field of photocatalysis,are studied.From the broad spectral response range and the quantum yield enhancement,the Bi2WO6/Ti O2 composite film is designed based on the nano-scale coupling response.And Bi2WO6/Ti O2 composite hollow microspheres.The Bi2WO6/Ti O2 composite film and hollow microsphere photocatalyst were characterized by XRD,SEM,UV-Vis,XPS and PL.The photocatalyst was used as the target degradation product for the film and The hollow microspheres were evaluated for visible light catalytic performance.From the macroscopic point of view,through the simulation reaction process,using the engineering related theory such as kinetic equation fitting,the catalytic degradation effect of the designed composite film and heterogeneous hollow microspheres on ethylene under visible light is studied.The microscopic analysis of the film and microspheres is carried out.The relationship between structure,properties and visible light photocatalytic activity;theoretically,the mechanism of Bi2WO6/Ti O2 composite film and heterogeneous hollow microspheres for photocatalytic degradation of ethylene was investigated.It provides theoretical and experimental basis for the preparation of visible light catalytic materials with special morphology,and opens up new ways for the removal technology of ethylene in the storage environment of fruits and vegetables,which lays a foundation for the development of new technologies for fruit and vegetable preservation.(1)The Bi2WO6/Ti O2 composite film was prepared by sol-gel combined with immersion-drawing method.The kinetic equation fitting and other engineering-related theories were used to investigate the film surface ratio,precursor sputum concentration,calcination temperature and time.The effect of activity is that when the film layer ratio is 3:1,the germanium source precursor concentration is 0.05mol/L,the calcination temperature is450°C,and the calcination time is 2h,the visible light catalyzed reaction rate constant K'value is the largest,which is 0.009636.At min-1,the degradation rate of ethylene reached20.53%,which was 2.4 times that of pure Bi2WO6 film and 5.4 times that of pure Ti O2 film.(2)The crystal phase composition,morphology and optical properties of Bi2WO6/Ti O2composite films with different film ratios were characterized.The average grain size of Ti O2and Bi2WO6 in Bi2WO6/Ti O2 films coated with Ti O2 was obtained.When the Bi2WO6/Ti O2film layer ratio is(3:1),the average grain size of Ti O2 and Bi2WO6 is 11.607 nm and 36.526nm,respectively,which is particularly significant.The band gap energies of Bi2WO6 and Ti O2 are 2.88 and 3.18 e V,respectively.The order of PL luminescence is Ti O2>Bi2WO6>Bi2WO6/Ti O2(4:1)>Bi2WO6/Ti O2(2:1)>Bi2WO6/Ti O2(3:1).The Ti element in the composite film is mainly present in the form of Ti4+.Ti2p1/2 and Ti2p3/2 are attributed to the Ti-O-W bond and the Ti-O-Bi bond,respectively.(3)The Bi2WO6/Ti O2 hollow microspheres were synthesized by mixed solvothermal method.The effects of preparation conditions such as Ti O2 coating amount,mixed solvent thermal reaction temperature and time on the visible light photocatalytic activity of ethylene were investigated by kinetic equation fitting and other engineering related theories.When the coating amount of Ti O2 is 15%,the reaction temperature is 160°C,and the time is 6h,the visible light catalytic reaction rate reaches the maximum,the rate constant K'is1.47×10-3min-1,and the degradation rate of ethylene reaches 29.56%.It is 1.69 times of Bi2WO6 hollow microspheres and 7.86 times of Ti O2 powder.(4)The crystal phase composition,micromorphology and optical properties of Bi2WO6/Ti O2heterogeneous hollow microspheres with different Ti O2 coating amount were characterized.The structure of the composite microspheres was loose and the cavity of the inner cavity was clearly visible.After coating,the oxygen vacancies and lattice defects on the surface of the heterogeneous microspheres increase,and Ti,Bi,and W share a part of oxygen atoms,forming Ti-O-Bi bonds and Ti-OW bonds.When the coating amount of Ti O2 is 15%,the maximum absorption edge of the composite sample is extended to 430.0 nm,and the forbidden band width of the composite microsphere is reduced to 2.884 e V.(5)Comparing the microstructure and macroscopic properties of Bi2WO6/Ti O2 heterojunction and Bi2WO6 and Ti O2 monomers with different morphologies,it is found that Bi2WO6/Ti O2heterogeneous hollow microspheres have wider spectral response range and superiority than pure Bi2WO6 and Ti O2.The photocatalytic activity,and the visible light catalytic activity of Bi2WO6/Ti O2 heterogeneous hollow microspheres is also higher than that of Bi2WO6/Ti O2film.It can be seen that the catalytic material with special morphology is beneficial to enhance its photocatalytic performance.The Bi2WO6/Ti O2 heterogeneous hollow microspheres have a narrower band gap,higher quantum efficiency,looser structure and stronger light-harvesting ability than the composite film,and the overall performance of the visible light photocatalytic activity is superior. |
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