Preparation Of Cerium Oxide Composite Material And Its Photocatalytic Performance

The rapid development of industry has benefited human society,but it has also brought some disadvantages to our life(e.g.water pollution).As one of the pollution sources of water pollution,organic pollutants not only endanger human health but also destroy the ecological environment.Therefore,the degradation of organic pollutants is one of the hot topics of concern for today’s society.Photocatalytic degradation is an efficient,environmentally friendly and low-cost treatment method,in which photocatalysts are the basis for the photocatalytic process,and the development of photocatalysts with excellent performance is the focus of this study.Cerium dioxide(CeO2),a wide bandgap n-type semiconductor material,has wide application as a photocatalyst for photocatalytic degradation of organic pollutants owing to its surface effect,quantum size effect,small size effect and excellent oxygen storage capacity as well as its special 4f shell layer electronic structure.However,CeO2 can only absorb UV light and a small amount of visible light due to its wide band gap,which has a low utilization of sunlight and lead to poor photocatalytic activity.According to the research,the energy band position,specific surface area and surface morphology of semiconductor photocatalysts can affect their photocatalytic activity.In this thesis,starting from CeO2,we took advantage its excellent properties to prepare composite materials with rGO and CdS,respectively,then prepare photocatalysts with high photocatalytic activity.Firstly,we based on hollow spherical CeO2 and coated its surface with rGO to improve its absorbance and carrier transport efficiency in the visible region,thus enhancing its photocatalytic performance.The photocatalytic activity of rGO/CeO2 was investigated by photocatalytic degradation of Rh B under simulated visible light,and it was found that the introduction of rGO did enhance the photocatalytic activity of the composites,but it also still has the problem of time-consuming.Therefore,we choose to incorporate a narrow band gap photosensitizer CdS,flower-like CeO2 as a carrier,and load CdS to prepare a flower-like CdS/CeO2 composite material with heterojunction formation,porous structure and larger specific surface area.It shown that the incorporation of CdS could broaden the light absorption band of CeO2 to the visible light region,and improved the utilization rate of the composite material to sunlight.The study found that the larger specific surface area and the special flower-like morphology increase the reactive sites of the composite material.The existence of the pore-like structure could improve the light-trapping ability of the composite material,and the formation of heterojunction could prolong the current-carrying capacity.and the lifetime of the electron(ie,the separation rate of photo-generated electron-hole).Therefore,the flower-like CdS/CeO2 composite exhibited excellent photocatalytic activity for the photocatalytic degradation of Rh B under visible light.There were completely different active sites based on different surface morphologies,and the density of active sites could affect the performance of the catalyst.Inspired by the flower-like CdS/CeO2 composite material,we carried out the third part of the work of this thesis.We first prepared the spherical-like CeO2,and CdS was incorporated to prepare the spherical CdS/CeO2 composite material.After photocatalytic degradation of Rh B,it was found that the spherical CdS/CeO2 composite material exhibited better photocatalytic performance than the flower-shaped CdS/CeO2 composite material.