Synthesis Of A₂Zr₂O₇?A=Bi,Y? Nanomaterials And Their Photocatalytic Activity Research

In recent years,researchers have been trying to find effective ways to control the increasingly serious environmental crisis and the excessive consumption of non-renewable source.Because of the advantages of green and clean,the technology of conversion of solar energy by photocatalysis has aroused great interest of researchers.However,the lower photocatalytic efficiency limits the application and development of photocatalysts.We know that the changes in the synthetic process have an important effect on the performance of the material.Therefore,the key factors that affect the photocatalytic properties of materials are explored through the synthesis process,so as to control the morphology by regular synthesis conditions in order to enhance the photocatalytic performance of the materials.This study can provide an important reference for the synthesis of photocatalytic materials.In this paper,we take the A₂Zr₂O₇?A=Bi,Y?type metal oxide materials as the research object,preparing the A₂Zr₂O₇ materials with photocatalytic activity by exploring different synthesis methods.The influence of the parameter changes in the process of preparation of the morphology and structure of the product was investigated,and the influence of the changes of the structure on the photocatalytic properties was explored.The main contents of this paper are as follows:?1?Bi₂Zr₂O₇ composite metal oxide semiconductor materials with visible light response were synthesized by coprecipitation method,and the as-synthesized materials were nanoparticles with sizes between 13²5 nm.The p H value of precursor solution in the preparation stage was changed,it was found that the concentration range of Bi³⁺in the mixed solution of 0.05⁰.2mol/L,precursor precipitation can be produced at p H>3.Adjusting temperature or time in the calcination stage,it was found that these two conditions changes would have a significant impact on the particle size and particle aggregation at the micro level,thus affecting the surface area of the material,and then affecting the photocatalytic performance of Bi₂Zr₂O₇.The experimental results showed that the performance of Bi₂Zr₂O₇ photocatalyst depends on the regulation of time and temperature in the process of synthesis.At the temperature of successful synthesis,the longer the calcination time,the more complete the crystal growth is,but it is unfavorable to the photocatalytic performance of Bi₂Zr₂O₇nanomaterials.The reason is that photocatalysis is a kind of surface reaction,and the more defects of the material,the more beneficial to prevent the recombination of photogenerated electrons and holes in the catalytic process.In addition,the smaller particle size leading to the higher surface area,thus the light absorption in the visible region is stronger,therefore gained the better photocatalytic activity.?2?Bi₂Zr₂O₇ composite metal oxide semiconductor materials with visible light response were synthesized by the molten salts method,and the synthesized materials were nanoparticles with sizes between 6¹2 nm.Mixing NaNO₃/KNO₃molten salts and precursor and then calcined them.On the one hand,it was found that adding molten salts can significantly reduce the synthesis temperature of the Bi₂Zr₂O₇ material,100 ^oC lower than that method without molten salts.On the other hand,compared with the materials synthesized without adding molten salts,the Bi₂Zr₂O₇ nanoparticles synthesized by molten salts method with more uniform particle size,and the majority of the size distribution is below 10 nm,contributing to the increased specific surface area,thus it has better photocatalytic performance.?3?Y₂Zr₂O₇ composite metal semiconductor materials with photocatalytic properties were synthesized by the citric acid combustion method.By adding citric acid?CA?as a combustion agent in the reaction system,Y₂Zr₂O₇nanomaterials of pure phase were prepared at low temperature for the first time.The reaction process route is green,clean and low energy-consumption.With the change of the amount of citric acid,the photocatalytic efficiency of the material has gone through a normal distribution trend.Citric acid is used as a combustion agent.When it is properly doped,the combustion is beneficial to make holes in the Y₂Zr₂O₇ nanocrystalline synthesis and increase the surface reaction area.Too much citric acid leads to the excessive carbon remains,which inhibits the activity of Y₂Zr₂O₇ nanocrystals,which is confirmed by light absorption tests and catalytic performance test.