Preparation Of BiOI/MnO₂ Composite And Photocatalysis Property

With the development of population and the rapid acceleration of industrialization process,environmental pollution,especially water pollution,has become one of the important reasons restricting the progress of human society.How to provide clean water resources to meet the needs of people's production and living is a huge challenge nowadays.The traditional treatment technology for water pollution has the disadvantages,such as high cost and high energy consumption,and there are some problems in the practical application of water treatment.Photocatalytic technology can utilize the advantage of photocatalytic materials to convert solar energy into chemical energy for the degradation of pollutants in water,and become a potential water pollution treatment technology.However,traditional photocatalytic materials,such as TiO₂ and ZnO,can only absorb ultraviolet light because of their wide band gap,and their utilization of sunlight is very low.In order to improve the utilization of visible light,photocatalysts responding to visible light have become one of the research hotspots.In order to improve the traditional BiOI photocatalyst with high photogenerated carrier recombination and serious photo-corrosion,the flower-like BiOI/MnO₂ heterojunction and the ternary flower-like BiOI/MnO₂/GO composition were constructed respectively to improve the activity and cycle performance of the catalyst.Firstly,the flower-like BiOI/MnO₂ heterojunction were fabricated by simple hydrothermal method and magnetic stirring at room temperature.The composition,morphology,structure and light absorption of the visible-light photocatalytic system were analyzed in detail by scanning electron microscopy,transmission electron microscopy,X-ray powder diffraction,X-ray photoelectron spectroscopy,fluorescence emission spectroscopy and ultraviolet-visible diffuse reflectance analysis.By the degradation of Rhodamine B,we can determin the optimal mass ratio.The photocatalytic mechanism of BiOI/MnO₂ under visible light was systematically studied by experiments on capturing active species.The results show that the spherical BiOI is loaded on the surface of flower-like MnO₂ in BiOI/MnO₂composite.When the mass ratio of BiOI to MnO₂ is 5:1,the photocatalytic degradation efficiency is the highest.RhB degradation efficiency can reach 99.18%within 60 minutes.After four cycles,the photocatalytic activity decreases slightly.According to the analysis of UV-Vis diffuse scattering spectrum and fluorescence emission spectrum,the absorption wavelength range of the composition to visible light becomes wider,and the recombination rate of photogenerated carriers decreases.The capture experiments of active species in the reaction system showed that the active species were·O₂^-and h⁺.This study provides a good reference for other BiOX.The modified Hummers method was used to prepare graphene oxide.Firstly,the flower-like MnO₂/GO composite were prepared by hydrothermal method using graphene oxide as precursor.Then,using the flower-like MnO₂/GO composite as precursor,the ternary flower-like BiOI/MnO₂/GO composition with different content of graphene oxide were prepared by room temperature precipitation.The photocatalytic activity of the ternary flower-like BiOI/MnO₂/GO composite for degradation of Rhodamine B was studied.The results show that flower-like MnO₂and graphene oxide are loaded together at first.Secondly,the spherical BiOI was loaded on the lamellaes of flower-like MnO₂ and graphene oxide.When the content of graphene oxide was 10 mg,the photocatalytic activity of BiOI/MnO₂/GO-10composite was the strongest.After 40 minutes of illumination,the degradation efficiency of BiOI/MnO₂/GO-10 composite for RhB reached 99.98%.According to the analysis of UV-Vis diffuse scattering spectrum and PL spectrum,the absorption wavelength range of the ternary composition becomes wider and the PL intensity decreases,which indicates that the separation efficiency of photogenerated carriers is improved.The capture experiments of active species showed that·O₂^-,h⁺and·OH were active species in the catalytic reaction system.