Preparation And Visible Light Photocatalytic Performance Of CdS-based Composite Photocatalytic Material

Photocatalysis technology is a high-efficiency,clean and low-energy technology that can use sunlight to decompose organic matter into inorganic matter at room temperature and pressure.It has been applied to solve many problems such as environmental pollution,especially the purification of polluted water bodies.The process photocatalyst plays a central role.Among them,CdS is in the narrow band gap semiconductor material,because it has a more suitable band gap position,the monomer CdS has a good photocatalytic effect.However,the photo-corrosion of CdS itself during the reaction continuously depletes the material,and the generated Cd²⁺further causes environmental pollution.Furthermore,only a small part of electrons and holes reach the surface of CdS,and most of them undergo continuous recombination,which leads to insufficient utilization of sunlight.To this end,we optimize the performance of CdS by preparing different semiconductor materials and compounding with CdS.The main research work of this paper are:（1）The rectangular parallelepiped NiWO₄ particles were prepared by hydrothermal method,and then small CdS particles were grown on NiWO₄by in-situ solvothermal method to obtain new CdS/NiWO₄composite samples.The photodegradation test results show that the composite material formed can efficiently degrade MG（93.5%,80 min）and MO（92.8%,120 min）;the TOC measurement of the solution after the reaction shows that the composite material has a good effect on both MG and MO.The mineralization decomposition capacity and the removal efficiency of organic matter are 72.4%and 68.2%respectively.And has good light stability.·O₂^-is the reaction substance.（2）The solvothermal method was used to obtain long rod-shaped CdS and flower-shaped Bi₂MoO₆,and then a simple stirring method was used to obtain Bi₂MoO₆/CdS composites with different mass ratios.The visible light degradation test shows that when the Bi₂MoO₆loading on CdS is 80wt%,the degradation performance and removal performance of the composite are the most excellent.The degradation efficiencies of MG and MO solutions are 95.6%and 94.7%,and the removal efficiencies are 76.3%and 71.4%.After 5 cycles of 0.8-BMO/CdS,the degradation efficiency of the sample to organic matter can still reach 88%.Through the energy band analysis of the material and the free radical capture experiment,·O₂^-and h⁺are the active substances in the reaction process,and the type II heterostructure formed can effectively reduce the recombination of carriers.（3）The long rod-shaped CdS with a length between 200 nm and 1μm was prepared by solvothermal method,and composited with the tetrahedral Pb WO₄ synthesized by hydrothermal method to obtain a Pb WO₄/CdS composite sample.The photocatalytic experiment results show that the degradation and removal efficiency of 1.0 PWO/CdS on MG within 80 min are 96.3%and 73.1%;the degradation and removal efficiency of MO within 120 min are 94.8%and 70.3%;After 5 times of light cycle experiment,the degradation efficiency can still reach 90%.Research on the mechanism of composite materials shows that CdS and Pb WO₄composite form a Z-scheme heterostructure,which separates carriers more effectively and effectively prevents the CdS itself from reacting with holes during the reaction,causing the material to be lost all the time.In the reaction process,·O₂^-and·OH are active substances,which have more excellent catalytic performance.