Preparation And Performance Study Of Transition Metal Sulfide Composite Photocatalyst

In recent decades,the whole world has been developing rapidly,especially the chemical industry is growing rapidly,and at the same time we are facing serious problems such as energy shortage and environmental pollution.An important way to effectively utilize solar energy is through the use of emerging technologies such as catalysis,which directly converts sunlight into chemical energy and is considered one of the most promising green technologies for sustainable energy and environmental remediation.Photocatalysis is an important means of generating clean energy by photocatalytic decomposition of water to produce hydrogen in a reaction driven by solar energy.Environmental pollution problems are also becoming more severe with the development of society,and one of the environmental pollutants that have received wide attention is tetracycline.Photocatalytic degradation of organic compounds such as tetracyclines provides a novel and convenient method for water purification.This thesis focuses on the use of transition metal disulfide MoS2-based composite photocatalysts for the efficient degradation of tetracycline and the efficient photolysis of aquatic hydrogen.Two-dimensional(2D)transition metal-disulfides(TMDs)are a class of semiconductor photocatalysts with excellent kinetic properties,which are promising photocatalytic materials due to their abundant resources,tunable band gap,good photocatalytic performance and appropriate redox potential.In this thesis,the idea of two MoS2-based composite photocatalysts,the modulation of structural morphology,structural characterization,heterogeneous structure construction and their performance are investigated.The studies are as follows:(1)By synthesizing oxygen-doped MoS2 layered nanomicrospheres by hydrothermal method,the generation of oxygen defects at specific sites in the semiconductor can further and improve the photogenerated electron-hole separation efficiency of the whole optical system.moS2 is a layered nanosphere,which exposes more active and stronger two-dimensional edge active sites on the surface of the sphere,thus improving the overall photocatalytic efficiency.Considering the morphological characteristics and energy band structure of MoS2 material and Bi2S3,this thesis further synthesizes MoS2/Bi2S3 composite photocatalyst by hydrothermal method.Bi2S3 is encapsulated on the outside of MoS2 in the structure of nanosheets,and the tightly bonded interface of the two materials can ensure stable electron transport and enhance the charge carrier separation efficiency,not only in the photocatalytic degradation of organic tetracycline The efficiency was improved and the hydrogen production efficiency also reached 423.24 μmol h-1 g-1 which was 4.49 and 6.48 times higher than that of the pristine MoS2 and Bi2S3.(2)In order to further optimize the photocatalytic performance of transition metal disulfide MoS2-based,In2S3,which matches the morphology and energy band structure of both MoS2 and Bi2S3,was added to the composite system in this thesis.The MoS2@In2S3/Bi2S3 composite photocatalyst was formed by simultaneously loading both Bi2S3 and In2S3 on the MoS2 surface by a one-step hydrothermal method and tuning the material ratios with different ratios to achieve the highest photocatalytic performance.The MoS2@In2S3/Bi2S3 composite accelerated the charge carrier transport and enhanced the light absorption intensity and range.The unique core-shell structure of the ternary composites increases the interfacial area and provides sufficient surface active sites for the photocatalytic reaction process.The MoS2@In2S3/Bi2S3 composites facilitate the photocatalytic process due to the enhanced broad-spectrum photoresponse and excellent photothermal effect,which facilitates the triggering of near-field temperature rise.And it showed an excellent photocatalytic hydrogen precipitation rate of 973.42 μmol h-1 g-1,which was 10 times higher than that of pristine MoS2.And the efficiency of tetracycline degradation reached 99.6%within 90 min.The enhanced photocatalytic performance can be attributed to the unique core-shell double Z-scheme tandem heterojunction structure promoting the transfer and spatial separation of photogenerated electron-hole pairs.In addition,the material exhibited excellent stability in cyclic stability experiments due to the suppression of photocorrosion of sulfides by the core-shell double Z-scheme tandem structure,thus indicating its potential practical application.