Preparation And Properties Of Bi₄O₅I₂/MoS₂ Photocatalysts

With the development of science and technology,energy shortages and environmental pollution have become serious issues.At the current stage,reasonable use of limited resources to effectively solve environmental problems is a hot topic.In recent years,semiconductor photocatalysis technology,as a green environmental protection approach,has been widely used for environmental governance and improvement due to its high efficiency,energy saving,strong mineralization ability,no secondary pollution,simple process and wide application range.Photocatalysis technology can effectively convert organic pollutants into non-toxic small molecular structures such as H₂O,CO₂,N₂,so as to achieve the purpose of pollutants mineralization.Currently,Bi OX(X=F,Cl,Br,I)has a highly anisotropic and layered structure(consisting of a[Bi₂O₂]plate intersected with a double halogen atom plate)and a satisfactory UV-vis spectral response range.Among them,the internal electric field of Bi₄O₅I₂photocatalyst can stimulate the rapid transfer of carriers to the catalyst surface,thus improving the separation efficiency of photoelectron-hole pairs.This thesis focused on Bi₄O₅I₂photocatalysts,and 2D transition metal sulfide Mo S₂was supported on a layered surface to prepare a composite photocatalyst.Mo S₂could effectively extended the photoresponse range to the near-infrared region.And at the same time,it could effectively improved the hole mobility of Bi₄O₅I₂and inhibited the recombination of carriers.The photocatalytic mechanism was explored by studied the degradation performance of pollutants.(1)The 3D flower layered mesoporous Bi₄O₅I₂/Mo S₂composite photocatalyst was prepared by oil bath method and calcination method.The mesoporous structure formed on the surface of Bi₄O₅I₂could effectively prolonged the electron lifetime,it provided more active sites for photocatalytic reaction.The heterojunction with narrow band gap?1.95 e V extended the light response to the near infrared region,and the photothermal effect was obvious due to the supported of Mo S₂.At the same time,this paper also explored the amount of Mo S₂introduced.In order to find the best composite ratio,2,4,6 and 8%were selected according to the mass ratio of Mo S₂in the composite material to control the best loading capacity.The crystal structure,elemental composition and photocatalytic performance of composite photocatalyst were studied.(2)The photocatalytic efficiency of Bi₄O₅I₂/Mo S₂in the degradation of highly toxic dichlorophenol and the reduction of hexavalent chromium was increased to 98.5%and 99.2%,respectively.About 4 and 7 times higher than the original Bi₄O₅I₂,respectively.The yield of photocatalytic hydrogen was 496.78?mol h^-1g^-1,6 times that of original Bi₄O₅I₂.The excellent photocatalytic performance can be attributed to the promotion of photothermal effect and the formation of dense Z-scheme layered heterojunction.In addition,the strong electron coupling effect generated by the Z-scheme heterojunction structure can establish an internal electric field between Bi₄O₅I₂and Mo S₂,improve the hole mobility of Bi₄O₅I₂,inhibit the recombination of carriers,and accelerate the transfer of carriers.