The Preparation And Visible-light Photocatalytic Performance Of Silver Silicate

Since the photocatalytic report,photocatalytic technology has made significant progress in the hydrolysis of hydrogen,degradation of organic pollutants,and reduction of carbon dioxide.Generally,in the case of illumination,the photocatalytic material absorbs light energy greater than the forbidden band width,and the electrons on the valence band are excited to transition to the conduction band,thereby leaving an equal amount of holes in the valence band.Then,the photogenerated electrons and holes migrate to the surface of the material,and react with the acceptor to form an active substance such as a superoxide radical and a hydroxyl radical to carry out a redox reaction.However,for photocatalytic materials,narrow photoreaction regions and low quantum efficiency are two important factors that restrict the development and industrialization of photocatalytic technology.After several decades of development of photocatalysis,in order to solve the problem of photoresponse of materials,ion doping,surface sensitization,precious metal loading and other means extend the photoresponse region into the visible range.In recent years,in order to improve the low quantum efficiency of photocatalytic materials,the concept of built-in electric field has been proposed.Since photogenerated electron holes tend to recombine when they migrate inside the material,when the material has a built-in electric field,it is possible to accelerate the separation of photogenerated electron holes in opposite directions,suppress the recombination of photogenerated electron holes,and improve the quantum efficiency.In this paper,the polar unit[SiO₄]is introduced into the material to construct a built-in electric field type photocatalytic material,and a highly efficient photocatalyst is obtained,which is mainly divided into five chapters:In this thesis,Ag₂SiO₃,Ag6Si₂O₇,Ag₁₀Si₄O₁₃3 samples were prepared by solid phase sintering,precipitation method and sol-gel method.The silver silicate compounds prepared by XRD pattern comparison were pure phase,and were analyzed by SEM and TEM.The particle size of the silver silicate compound is divided into 1-3μm,20-50 nm,and 20-50 nm.The sample was subjected to XPS test,and no other elements were found in the total XPS spectrum,indicating that the prepared sample was a pure sample;in the three Si 2p XPS spectra,there were characteristic peaks of about 103.25 eV,belonging to[SiO₄]The valence state of Si,which indicates the successful introduction of the polar unit of silicon tetrahedron,in the Ag 3d XPS spectrum of the three materials,the existence of elemental Ag0 was not found,all of which were Ag+valence.This indicates that the light absorption capacity and catalytic activity of the sample are all from the material itself,and the plasmon resonance effect of the noble metal does not occur.Through the UV-visible diffuse reflection test,the light absorption edges of the three Ag₂SiO₃,Ag₆Si₂O₇,and Ag₁₀Si₄O₁₃3 samples were 678 nm,652 nm,and 588 nm,respectively,which were all visible light catalyzed materials.The bandwidths are 1.51 eV,1.57 eV,and 1.74 eV,respectively.The photocatalytic degradation of methylene blue was carried out on the sample.Compared with P25,the silver silicate sample showed excellent photocatalytic activity.The catalytic activity of each sample was compared:Ag₁₀Si₄O₁₃>Ag₆Si₂O₇>Ag₂SiO₃>P25.The specific surface area pores of the samples were determined,Ag₂SiO₃ was 3.279 m²/g,Ag₆Si₂O₇ was 24.492 m²/g,and Ag₁₀Si₄O₁₃3 was 22.911 m²/g.The open circuit voltage of the sample was measured by electrochemical experiments,the surface charge of the sample was measured by a charge meter,and the size of the built-in electric field of each sample was compared by theoretical calculation.Based on the measured data,the catalytic activity of silver silicate compounds was analyzed.The built-in electric field strength of Ag₆Si₂O₇ and Ag₂SiO₃ was not much different,mainly due to the particle size and specific surface area of the material contributing to the photocatalytic performance.The particle size,specific surface area and particle size of Ag₁₀Si₄O₁₃3 and Ag₆Si₂O₇ are not much different,and the built-in electric field size plays an important role in the catalytic activity of the material.The energy band positions of Ag₂SiO₃,Ag₆Si₂O₇,and Ag₁₀Si₄O₁₃3 were calculated by the formula.The analysis of elemental silver precipitation from the XRD pattern may be due to the reduction of silver ions in Ag_xSi_yO_z to silver by photogenerated electrons.Finally,the paper summarizes and forecasts.Summarize the work done in this paper and the conclusions of the analysis,analyze the problems that arise at this stage,and point out the direction and work content for the next stage of research content.