Preparation Of CeO₂-based Composite Photocatalytic Material And Study On Photocatalvtic Reduction Of CO₂

Excessive emission of CO₂breaks the natural carbon cycle and brings serious environmental problems.Under the action of solar energy,carbon dioxide is converted into hydrocarbons such as CO and CH₄through effective photocatalysts,which can not only alleviate the problem of energy shortage,but also help improve the greenhouse effect.However,in the field of photocatalytic reduction of CO₂,photocatalysts generally have problems such as poor CO₂adsorption capacity and low catalytic efficiency.Therefore,it is necessary to further develop a catalyst with high efficiency.As a common semiconductor material,CeO₂is used in the field of photocatalysis due to its advantages such as easy synthesis,environmental protection,and good performance.It is worth noting that CeO₂itself also has defects such as low visible light response and easy recombination of photo-generated carriers,which limit the improvement of its photocatalytic performance.Therefore,on the basis of CeO₂-based semiconductor materials,this thesis synthesized a high-efficiency photocatalytic reduction of CO₂catalyst through the adjustment of CeO₂structure and the compounding of semiconductor materials.The content is mainly divided into the following two aspects:（1）The CeO₂@MoSe₂hollow composite photocatalytic material rich in oxygen vacancies and selenium vacancies was prepared by precipitation method and hydrothermal method.The hollow structure of the composite photocatalyst increases the specific surface area of the material and improves the CO₂adsorption capacity;at the same time,the unique hollow structure can make the light reflect multiple times in the cavity,thereby improving the light utilization efficiency.The introduction of vacancies is conducive to the capture of electrons by CO₂and promotes the process of photocatalytic reduction of CO₂.Then,the CeO₂@MoSe₂heterojunction formed by introducing the narrow band gap semiconductor MoSe₂increases the absorption range of visible light and improves the separation efficiency of photogenerated carriers.Moreover,both pure CeO₂and Mose₂only produce a small amount of CO without the production of other hydrocarbons,but the synergistic effect of the composite material increases the amount of CO produced and produces CH₄.（2）Prepare the CeO₂@In₂O₃hollow composite photocatalytic material rich in oxygen vacancies by the calcination method and analyze the performance of the photocatalyst to reduce CO₂.Through a series of characterization tests,it is shown that the photocatalytic performance of CeO₂@In₂O₃composites is better than CeO₂and In₂O₃.When the loading of In₂O₃is 22.5 wt%,the 4h yields of CO and CH₄are the highest,respectively 38.7μmol g^-1and 7.8μmol g^-1,the output of CO is more than twice that of CeO₂,and CH₄has realized the process from scratch.In₂O₃and CeO₂form a heterogeneous structure on the surface of the material,which reduces the photo-generated electron-hole recombination rate and greatly improves the photocatalytic performance.