Synthesis And Research Of Heterojunction Photocatalyst Integrating Photothermal And Upconversion Thermometric Functions

Facing the increasingly severe environmental pollution and energy crisis in the word,the exploration of new and efficient photocatalyst is an important topic in the field of photocatalysis.In order to improve the utilization efficiency of soalr energy,broadening the spectral absorption range of semiconductor photocatalyst is the most direct strategy.As the spectral absorption of semiconductor photocatalysts extends to the near-infrared region,while the solar energy is converted into chemical energy through photocatalytic reaction,part of the energy will also be converted into heat through photo-thermal effect,which causes the temperature of the catalyst surface to change and affects the photocatalytic reaction process.This thesis aims to construct a direct Z-scheme heterojunction by combining the energy band-matched semiconductor matrix up-conversion luminescent material wiht a narrow band gap semiconductor photocatalyst,in which the photocatalytic performance is not only improved but the fluorescence intensity ratio（FIR）thermometric function is introduced.It provides a potential micro-nano material platform for realizing in-situ temperature sensing on the surface of the narrow band gap photocatalyst,which can further to explore the generation of the photo-thermal effect and its influence mechanism on the photocatalytic reaction.This thesis includes the following three parts:（1）The typical layered bismuth oxyhalide monomer Bi OBr was selected as the research object.A narrow band gap black OV-Bi OBr nanosheets with exposed the{001}crystal facet and rich in oxygen vacancies were synthesized by solvothermal method.On the basis of OV-Bi OBr,the direct Z-scheme homo-junction photocatalyst OV-Bi OBr@Bi OBr with visible light response was further synthesized by hydrothermal method,which has the improved performance in both the photocatalytic degradation of rhodamine B（Rh B）and the oxygen production of photolysis of water.Then,combining experimental characterization with First-Principles calculations,the Z-scheme electron transfer mechanism was systematically studied,which laid the experimental and theoretical foundations for constructing a multifunctional photocatalyst based on the direct Z-scheme heterojunction.（2）A tetragonal Bi VO₄ semiconductor with wide band gap and moderate phonon energy was selected as the upconversion luminescent matrix and the spindle-shaped Yb³⁺/Er³⁺co-doped tetragonal Bi VO₄ nanomaterial with uniform morphology was prepared by hydrothermal method.Under the excitation of 980 nm laser,the FIR temperature sensing performance and photothermal conversion ability based on the Er³⁺of samples were systematically studied,and the basic principles of temperature sensing and heat generation were explained in combination with the up-conversion process.Then,through in vitro experiments,the in-situ self-heating temperature monitoring function of the nanoparticles was demonstrated in the chicken breast tissue with a depth of 1.5 mm,which laid the experimental and theoretical bases for constructing the direct Z-scheme heterojunction as an in-situ temperature sensing platform.（3）In order to obtain a direct Z-scheme heterojunction photocatalyst that integrates photothermal/temperature sensing functions,Bi VO₄:Yb³⁺/Er³⁺@OV-Bi OBr was obtained by a two-step method of hydrothermal-solvothermal,which combined the narrow band gap OV-Bi OBr nanosheets with the wide band gap semiconductor material Bi VO₄:Yb³⁺/Er³⁺upconversion microrods.And the photocatalytic degradation performance,FIR temperature sensing ability,photothermal conversion property and Z-scheme electron mechanism of the heterojunction were systematically studied.Then,the influence of external environmental temperature changes on the photocatalytic degradation of Rh B was explored,which explained the importance of utilizing the heterojunction in-situ temperature sensing platform in the field of photocatalysis.