Research On The Preparation And Photocatalytic Performance Of Dye Sensitized Sn In4s8 Based Nanocomposite Materials

In the modern society,human industrial civilization constantly evolving,environmental degradation and energy shortage have become major challenges for the sustainable development of industrial civilization.With the development of science and technology,people have found that photocatalytic technology has shown many advantages in the fields of pollution degradation and hydrogen production.Therefore,the emergence of semiconductor photocatalysis technology,to a certain extent,is considered to be the most promising technology in the field of environmental degradation and energy shortage.However,the conventional photocatalysts such as TiO₂ and ZnO have a large forbidden band width and can only respond to ultraviolet light,which only takes up4%energy of solar carries.Therefore,it is very meaningful to develop a photocatalyst with a visible light response,high stability,and excellent photogenerated electron-hole separation ability.Ternary metal sulfide AB_mC_n（A=Zn,Cd,Cu,Ag,Sn,etc.;B=Al,Ga,In;C=S,Se,Te）is a new chalcogenide catalyst with unique optoelectronics performance and catalytic performance:narrow band gap,high stability,convenient shape control.Among them,SnIn₄S₈ is a typical ternary sulfide photocatalyst with high efficiency and stability.However,the rapid reorganization of light production pairs:electrons and holes is also the uniform defect to most semiconductors.At present,modification methods such as metal or non-metal doping,fabrication of nano-structures,heterostructure formation and dye sensitization effectively suppress the recombination between photogenerated electrons and holes.Although,the dye sensitized SnIn₄S₈ semiconductor has never been researched.This paper mainly uses phthalocyanine and squaraine sensitizes the SnIn₄S₈ semiconductor.The overall research content of this paper is broken down as follows:（1）The SnIn₄S₈ semiconductor material was synthesized by solvothermal method.The morphology of the SnIn₄S₈ semiconductor material was globular.The SQ with conjugated structure was used as the sensitizer.The BSQ/SnIn₄S₈ composite photocatalyst was prepared by ultrasonic impregnation.It was found by scanning electron microscopy and transmission electron microscopy that the sheet-like dye adhered to the surface of the semiconductor,thereby increasing the transfer rate of photogenerated electrons.Under the visible light irradiation,we degraded the malachite green to detect the photocatalytic performance of all samples.（2）Under the premise that BSQ sensitized SnIn₄S₈ material can enhance the photocatalytic activity,we continue to study the effect of substituent groups on the photocatalytic properties of conjugated systems.We have synthesized a series of symmetric squaraine dyes such as:anthraquinone acid ISQ,methyl sulfonium sulphate MSQ,fluoro sulfonium squaraine FSQ,carboxy sulfonium sulphate CSQ and benzofluorene sulphate BSQ.SQs/SnIn₄S₈ composite photocatalyst was prepared by ultrasonic impregnation.Using malachite green as the material to be degraded,the photocatalytic properties of pure and supported samples were systematically studied.The HOMO-LUMO energy levels of different dyes were obtained by Gaussian simulation and the electron density distribution map was obtained.The effect mechanism of the catalyst was further studied.The experimental results show that the energy level and the degree of conjugation of the dye molecules take influence on the photocatalytic performance of the material（3）The phthalocyanine dye with larger molecular system was selected as the sensitizer to modify the SnIn₄S₈ semiconductor material,and the CoTNPc/SnIn₄S₈ material was prepared by ultrasonic impregnation.The flaky cobalt phthalocyanine dye adhered to the surface of flower-like SnIn₄S₈.Under visible light conditions,the degradation efficiency and the thermal stability of CoTNPc/SnIn₄S₈ nano-composite shown to be improved.The photocatalytic results show that the CoTNPc/SnIn₄S₈ complex has stronger light absorption properties.The matching band position between CoTNPc and SnIn₄S₈ is beneficial to the enhancement of photocatalytic activity.（4）Preparation and study of ternary SnIn₄S₈ based materials.The synthesis of carbon nitride is based on melamine and ammonium chloride as a leavening agent.The carbon nitride of the release layer is synthesized under high temperature calcination.Then the SnIn₄S₈/g-C₃N₄ composite is prepared by low temperature co-precipitation.CoPc@SnIn₄S₈/g-C₃N₄three-phase composite photocatalyst was synthesized by ultrasonic impregnation.The new CoPc@SnIn₄S₈/g-C₃N₄ three-phase composite photocatalyst can be used for not only photolysis of hydrogen in water but also for degrading pollutants.The photocatalytic mechanism of CoPc@SnIn₄S₈/g-C₃N₄ three-phase composite photocatalyst was studied in depth.