Interface Regulation of Semiconductor Enhances Photocatalytic Performance

Author:Gao Ge

Supervisor:xu jing wei


Degree Year:2019





Energy crisis and environmental pollution are becoming increasingly more and more serious.How to solve these problems simply and efficiently has aroused extensive research by researchers.Photocatalytic technology,using renewable and pollution-free solar energy as energy source and semiconductor nanomaterials as catalyst,can realize the conversion of solar energy to chemical energy through simple and easy-to-operate photocatalytic reaction.Therefore,it has become the most ideal and effective way to solve energy and environment problems.In addition,the catalyst is the most important component to determine the photocatalytic performance in the process of photocatalytic reaction.In this paper,based on the theory of semiconductor heterostructure fabrication and the characteristics of semiconductor nanomaterials,we have solved the problems of photogenerated electron-hole recombination,narrow spectral absorption range,insufficient research on application range and low catalytic efficiency semiconductor nanomaterials[zinc oxide(ZnO),inorganic perovskite quantum dots(CsPbX3 QDs,X=Cl,Br,I),metal organic framework materials(MOFs)]by heterostructure fabrication or further heterojunction interface regulation.Then these nanomaterial catalysts are applied to the photocatalytic degradation of organic pollutants,and some progress has been made.The specific research work includes:(1)High-efficiency PbS/ZnO,CdS/ZnO,CdSe/ZnO heterojunction composite catalysts were prepared by in situ growth of PbS/CdS/CdSe quantum dots on a three-dimensional ZnO nanotube array through chemical deposition method.By adjusting the deposition times of quantum dots,heterojunction composite catalysts loaded with different content of quantum dots were prepared,and these catalysts were used for photocatalytic degradation of methyl orange.The systematic photocatalytic experiments show that the PbS/ZnO heterojunction composite catalyst has the highest photocatalytic activity compared with the pure ZnO and the composite catalyst CdS/ZnO(or CdSe/ZnO),which can degrade methyl orange almost 100%in 30 minutes.(2)Inorganic perovskite quantum dots[CsPbX3 QDs(X=Cl,Br,I)]were synthesized by room temperature supersaturated crystallization and used for the first time in the photocatalytic degradation of methyl orange.Photocatalytic experiments were carried out to study the catalytic properties of these three different inorganic perovskite quantum dot catalysts(CsPbCl3 QDs,CsPbBr3 QDs and CsPbl3 QDs)and the same inorganic perovskite quantum dot catalysts with different contents in the photocatalytic degradation of methyl orange.The experimental results show that the smaller size CsPbCl3 QDs(1.5 mg added)has the best photocatalytic oxidation activity,which can degrade the methyl orange solution from orange-yellow to a colorless solution within 100 min.(3)The composite catalyst AuNC@ZIF-8(Cu)NRAs was synthesized on a foamed nickel substrate by bottom-up method.It was found that the surface charge of the encapsulated Au nanoclusters could be adjusted by doping Cu at the unsaturated metal sites in the ZIF-8 matrix composites.After the surface charge was adjusted,the Au nanoclusters are positively charged and more easily combine with hydrogen atoms to form Au-H intermediates.Then,the catalytic performance of the composite catalyst in the hydrogenation reduction of nitrobenzene compounds was improved.The experimental results show that compared with the catalysts AuNC@ZIF-8,ZIF-8(Cu)NRAs and Au NP,the catalytic reduction performance of AuNC@ZIF-8(Cu)NRAs on nitrobenzene compounds is significantly improved,and the degradation rate can reach 98%in 6 min.At the same time,the studies on the application range of AuNC@ZDF-8(Cu)NRAs show that this composite catalyst also exhibit excellent catalytic ability for the reduction of other nitrobenzene compounds such as 3-nitrophenol,2-nitrophenol,nitroaniline and dinitrobenzene.In addition,after 10 cycles of experiments,the results show that the catalytic reduction activity,stability and morphology of the catalyst have not changed significantly,which proves that the composite catalyst has excellent stability.