Preparation And Properties Of Keggin-type Polyacid-based Composite Photocatalysts

Environmental pollution is becoming more and more serious,and people's requirements for high-quality life are getting higher and higher,which makes us must vigorously develop environmentally-friendly functional materials to control the environment,reduce pollution and meet people's growing requirements for high living standards.A broad-spectrum antibiotic has emerged,and tetracycline(TC)is widely used in daily life and is overused due to its tolerance.However,due to inappropriate treatment methods,or even direct discharge into the water environment,the water environment is seriously polluted.At the same time,the abundance of heavy metals in the water environment has severely polluted the water quality,and the living environment of living organisms on the earth is always in jeopardy.Therefore,we urgently need to develop a renewable and more environmentally friendly new energy source for environmental problems to control the polluted environment.As a representative of this form of energy,solar energy has always been favored by experts and scientists.In recent years,photocatalytic reactions have been effectively used in the decomposition of pollutants in water and the production of hydrogen through the photocleavage of water.The Keggin-POM studied in this paper has attracted much attention because of its adjustable band gap structure and excellent redox capacity,but its application is limited due to its low utilization of light.In this paper,the hollow Keggin-potassium phosphomolybdate(KMoP)was prepared by hydrothermal method,and then CdS and Bi₂S₃ were loaded in water bath to form KMoP/CdS/Bi₂S₃ tandem heterojunction.At the same time,the photocatalytic performance was tested by the reduction of Cr⁶⁺and the degradation of TC.The research contents of this paper are as follows:(1)KMoP,with a hollow structure,was prepared by a hydrothermal method,and then KMoP/CdS heterojunction was prepared for the first time by optimization.In addition,a series of characterizations of the properties of the binary heterojunction has been performed.The reduction rate of Cr⁶⁺,the decomposition rate of TC,and the hydrogen production capacity of the photocatalyst can reach 52.2%,61.9%,and 2.21mmol h^-1 g^-1,respectively,and it had good stability.This is because KMoP/CdS will form a Z-type heterojunction when irradiated with visible light,which promotes the separation of photo-induced electron-hole pairs.Thus,a stable electron flow is provided for the photocatalytic degradation,which promotes the photocatalytic efficiency and the stability of the photocatalyst.(2)The hollow ternary heterojunction KMoP/CdS/Bi₂S₃ was prepared in a water bath state.Compared with pure KMoP,its optoelectronic and photocatalytic properties were improved,which was mainly due to the photo-thermal effects of the photocatalyst.Through the photocurrent test,electrochemical impedance spectra test and work function test of the catalyst,it was proved that KMoP/CdS/Bi₂S₃ had the best photoelectric performance.The photocatalytic degradation experiments showed that the reduction efficiency of Cr⁶⁺can be as high as 95.5%,and the degradation rate of TC can reach 97.5%,which are 3.47 and 3.41 times that of pure KMoP,respectively.And the H₂release rate was 8.31 mmol h^-1g^-1.The obtained KMoP/CdS/Bi₂S₃ photocatalyst also had high stability,indicating that the construction of ternary heterojunction can further enhance its photocatalytic performance.