Development Of Multicomponent Metalchalcogenides/layered Double Hydroxide Composites And Investigation Of Thecatalytic Properties

Photocatalytic technology is characterized by the ability to produce chemical energy,decompose organic pollutants,and detoxify heavy metal contamination by utilizing solar energy.Although the research on photocatalysis has made great progress in the past few decades,it is still a great challenge to develop photocatalysts with high catalytic activity.One of the bottlenecks restricting the performance of this environmentally friendly technology is the efficient recombination of photogenerated electrons and holes.Moreover,it is a hot issue in this field to explore the construction of semiconductor composite photocatalyst to overcome the deficiency of single semiconductor and obtain high efficiency photocatalyst.In this thesis,Cd In₂S₄/NiCr-LDH,Cd In₂S₄/In（OH）₃/NiCr-LDH and Zn In₂S₄/NiCr-LDH composite photocatalyst composed of layered double metal hydroxide（LDHs）supported multicomponent metal chalcogenides is mainly studied.（1）A series of NiCr-LDH were prepared by hydrothermal method,and the photocatalytic performance was analyzed by the photocatalytic generated H₂ from water splitting.A series of Cd In₂S₄/In（OH）₃/NiCr-LDH composite samples were prepared by hydrothermal method at 180°C using the most efficient sample（denoted as NC-180）as raw material.The effects of sulfur source concentration and NiCr-LDH content on the photocatalytic performance of the composites were explored through photocatalytic reduction of Cr（Ⅵ）and the photocatalytic generated H2 from water splitting,and the internal mechanism was deeply analyzed.The ternary composite sample Cd In₂S₄/In（OH）₃/NiCr-LDH（denoted as HP-180）prepared with 1.667 g/L NC-180 and 0.007 M thioacetamide showed the highest performance.The photocatalytic generated H2 from water splitting efficiency is 10.9 times that of Cd In₂S₄,58.7 times that of NiCr-LDH,and 2.06 times that of Cd In₂S₄/NiCr-LDH.Moreover,the photocatalytic removal Cr（Ⅵ）efficiency of the ternary composite sample is 97%,which is much higher than 6%of NiCr-LDH and 75%of Cd In2S4.The enhanced photocatalytic activity of Cd In₂S₄/In（OH）₃/NiCr-LDH samples can be attributed to the existence of a large number of interfaces with local band staggering distribution,which provides a variety of paths for the separation and transfer of photogenerated electron-hole pairs and effectively inhibits the carrier recombination to promote the improvement of catalytic performance.In conclusion,this study provides a simple way to produce low-cost and high composite photocatalytic materials.（2）Zn In₂S₄ and NiCr-LDH were prepared by coprecipitation method,and Zn In2S4/NiCr-LDH composite samples were prepared by electrostatic self-assembly method based on their opposite surface charges.XRD,SEM,TEM,XPS,BET,Zeta potential and other methods were used to characterize the properties of composite samples and explore their photocatalytic removal Cr（Ⅵ）efficiency.Pseudo-first-order kinetics and pseudo-second-order kinetics were used to fit the removal efficiency data of the samples in Cr（Ⅵ）solution with different concentrations.The adsorption rate of Cr（Ⅵ）by Zn In2S4/NiCr-LDH was 70%,which is 5.2 and 1.9 times that of Zn In2S4 and NiCr-LDH,respectively.The adsorption rate for Cr（IV）was 93%of the original after three cycles of use.The composite sample of Zn In2S4/NiCr-LDH showed the best photoreduce Cr（Ⅵ）efficiency of 47.2%.