Study On Modification Of Rutile TiO₂ And Its Photocatalytic Activity Mechanism

At the beginning of the new century,the contradiction has become more and more prominent between environment and development.All countries are actively exploring the road to sustainable development,and the prerequisite for sustainable development is to properly deal with the relevance of development and the environment.As an environmentally friendly technology,photocatalytic technology has received unprecedented attention from various countries and organizations.Among many photocatalysts,TiO₂ has many advantages such as high photocatalytic activity,high thermodynamic stability,non-toxicity and low cost,and is widely used.However,due to various reasons,the photocatalytic activity of TiO₂ cannot be fully exerted,so this article aims to modify TiO₂ and study the photocatalytic mechanism of rutile TiO₂.In this paper,rutile TiO₂-BiOBr and anatase TiO₂-BiOBr were synthesized by in-situ synthesis method,that is,nano-TiO₂ particles were deposited on the sheet-like BiOBr,and their mass ratio was 1:1.After coupling with BiOBr,the photocatalytic performance of rutile TiO₂ was greatly improved,and the same photocatalytic effect as anatase TiO₂ was achieved.The apparent degradation rate of methyl orange by anatase TiO₂-BiOBr under simulated sunlight is 1.6 times that of anatase TiO₂ alone and 6.3 times that of BiOBr alone.In addition,the samples were characterized by DRS,EIS,bet and PL to explore the reasons for performance improvement.The results show that compared with anatase TiO₂-BiOBr,rutile TiO₂-BiOBr has narrower band gap,smaller impedance and weaker photoluminescence intensity,which indicates that rutile TiO₂-BiOBr will be easier to produce photo-generated hole-electron pairs,and photo-generated charges will migrate faster and separate more effectively.However,the specific surface area of rutile TiO₂-BiOBr is smaller than that of anatase TiO₂-BiOBr,which will make the photocatalytic effect of rutile TiO₂-BiOBr difficult to surpass that of anatase TiO₂-BiOBr.In addition,the active substance capture test shows that the hole is the main active substance.In addition,this paper has developed a new method for preparing rutile TiO₂,and it has shown excellent photocatalytic activity.Under the same photocatalytic conditions,the degradation rate of anatase TiO₂ was 0.0375 min^-1,while the degradation rate of rutile TiO₂ reached 0.0753 min^-1.Since this method is prepared by hydrothermal reaction in a strong acid and low temperature environment,we believe that the main reason for the excellent performance of the prepared rutile TiO₂ is the introduction of surface oxygen vacancies.Therefore,we calcined the prepared samples at different temperatures and different atmospheres to construct rutile TiO₂with different surface oxygen vacancy concentrations,and performed XPS and EPR characterization to determine the existence and concentration of surface oxygen vacancies.Additionally,XRD,TEM,and SEM characterizations were performed to examine the effect of surface oxygen vacancies on sample structure and morphology.Furthermore,DRS,MS,EIS,BET,PL and other characterizations were performed to study the effect of surface oxygen vacancies on various physical and chemical properties of the sample.Based on the assumption of surface oxygen vacancies,we constructed a supercell of 2×2×3 rutile TiO₂,and processed the supercell to expose the main plane（110）of the rutile TiO₂ to the surface.Different concentrations of oxygen vacancies were constructed on（110）,and DFT calculations were performed using simulation software（VASP）.According to DFT calculation,the introduction of surface oxygen vacancies causes the Fermi surface to move to the bottom of the conduction band,which will facilitate the transfer and separation of photogenerated charges,and the band structure near the Fermi surface changes,resulting in a phenomenon similar to the impurity level.In addition,the test results show that the microscopic morphology of the sample is changed after the introduction of surface oxygen vacancies,and the visible light absorption capacity of the sample is enhanced,the impedance is reduced,and the photo-generated charge separation efficiency is increased.These are all conducive to improving the photocatalytic performance of the sample.Based on DFT calculations and experimental results,we believe that the introduction of surface oxygen vacancies is the main reason for the excellent photocatalytic performance of rutile TiO₂.This unique and innovative work breaks the traditional concept of rutile TiO₂ and provides a theoretical possibility for rutile TiO₂to be applied to other research fields.