Construction And Photocatalytic Properties Of Sulfide-based Nanocomposites With Wide-spectrum Response

Compared with metal oxides widely used in the field of photocatalysis,metal sulfide has a relatively narrow band gap,which can improve the shortcomings of most metal oxides that cannot use sunlight efficiently.Among them,bismuth sulfide（Bi₂S₃）,as a narrow band gap sulfide semiconductor,has good visible light absorption performance,so it is a promising photocatalyst for photoelectrochemical water-splitting and environmental remediation.However,due to the rapid photogenerated photoelectron-hole recombination,its photocatalytic application is hindered.The development of photocatalytic materials with high efficiency,stability and wide spectral response is of great significance to realize the practical application of semiconductor photocatalysis technology.In this thesis,we constructed the heterojunction between Bi₂S₃and other semiconductors with wide band gap or precious metals,which broadened the spectral absorption range of the composite photocatalytic materials and improved the photogenerated carrier separation efficiency,and then enhanced the photocatalytic performance.The main research contents are as follows:Two-dimensional sheet-like Bi OBr with highly exposed（001）facets was synthesized by solvothermal method.Using sodium diethyldithiocarbamate trihydrate（Na DDTC）as vulcanizing agent,Bi₂S₃/Bi OBr composite material was synthesized by ion exchange process.The photodegradation properties,cycle stability and degradation mechanism of cationic dyes Rhodamine B（Rh B）,methylene blue（MB）and anionic dyes methyl orange（MO）were investigated.The results showed that the prepared Bi₂S₃/Bi OBr composites showed the best degradation performance when curing time was 4 h,and the degradation efficiency of Rh B,MB and MO was 9.50,7.64 and 12.61 times that of Bi₂S₃ respectively.And it had good reusability.The efficient composite photocatalytic materials prepared in this work have potential applications in the removal of organic pollutants in sewage.The Ag/Bi₂S₃ composite photocatalytic material with three-dimensional flower-like morphology was successfully prepared by solvothermal and photoreduction method.The Ag/Bi₂S₃ composite material had excellent light absorption capacity in the wavelength range of 200-800 nm,which was favorable for the formation of photogenerated electron-hole pairs.The catalyst showed excellent photocatalytic reduction activity of Cr（Ⅵ）under visible light irradiation,and the reduction efficiency of Cr（Ⅵ）could reach 99.23%within 35 min,which was 3.26 times that of pure Bi₂S₃.The reasons for the improvement of photocatalytic efficiency were that the absorption of visible light was enhanced and the Schottky junction was formed after the introduction of Ag,which effectively improved the separation and transmission rate of photogenerated electrons and holes.The nanocomposite had good cyclic stability and reusability.The Ag/Bi₂S₃ composite material has wide application value in sewage treatment and other fields.The Z-scheme Ag₃PO₄/Bi₂S₃ composite photocatalytic material was successfully synthesized by in-situ deposition of Ag₃PO₄ nanospheres on three-dimensional flower-like Bi₂S₃.The photocatalyst had a wide spectral absorption range,and could efficiently degrade Rhodamine B and methyl orange under visible light irradiation.The degradation efficiency of Rhodamine B and methyl orange was 19.02 times and 15.84 times that of the original Bi₂S₃ respectively.Cyclic experiments showed that the photocatalytic stability of Ag₃PO₄/Bi₂S₃ composite material was significantly improved compared with pure Ag₃PO₄,indicating that the introduction of Bi₂S₃ could effectively inhibit the photocorrosion of Ag₃PO₄.This work has good development prospects in the design of Z-scheme Bi₂S₃-based photocatalyst and in the field of controlling organic pollutants in sewage.