Study On The Performance Of ZnSnO₃/Zn₂SnO₄ Piezoelectric Catalytic Production Of H₂O₂ And Its Influencing Factors

Hydrogen peroxide（H₂O₂）is a kind of green oxidizer and clean liquid fuel,which has great application potential in chemical industry,biomedicine,environmental treatment and chemical synthesis,etc.The traditional production technology of hydrogen peroxide has certain pollution to the environment.Green synthesis of H₂O₂using renewable energy has aroused unprecedented research value and hotspot.Piezoelectric materials are typically characterized by non-central symmetry in their crystal structure.When external stresses are applied,piezoelectric polarization results in charge flow.Because the crystal structure of perovskite fits perfectly with the electron distribution of the outermost layer of lead,piezoelectric materials are often lead-containing perovskite oxides.However,the application range of lead-bearing piezoelectric materials is limited due to their toxicity.As a typical piezoelectric lead-free material,Zn Sn O₃perovskite structure material and Zn₂Sn O₄spinel structure material are two typical piezoelectric lead-free materials,using their vibration-induced electron migration ability to produce H₂O₂.Zinc stannate（Zn Sn O₃and Zn₂Sn O₄）,commonly known as zinc tin oxide,has unique physical and chemical properties,such as high electron mobility,high electrical conductivity,attractive optical properties and good stability,so it has been a hot spot in the exploration and research of micro and nano structures.The excellent composite properties of zinc tin oxide and the micro and nano structures of crystal phase and morphology have been widely used in the fields of solar cells,sensors,cathode materials for lithium batteries,nanodevices and catalysts.However,the research reports in the field of piezoelectric catalytic production of H₂O₂are little known so far.This paper will mainly study the performance and influencing factors of zinc tin oxide in H₂O₂production,and the specific research contents are as follows:（1）Three-dimensional Zn Sn O₃and Zn₂Sn O₄materials were synthesized by hydrothermal method,and the morphology of the two materials was characterized to explore the differences.The piezoelectric H₂O₂production performance of the two materials was tested by ultrasonic cleaning,and combined with electrochemical testing and solid fluorescence testing,to explain the differences in piezoelectric properties of the two materials.The experimental results show that the electron-hole recombination ratio of Zn Sn O₃material is lower than Zn₂Sn O₄material,so the piezoelectric properties of Zn Sn O₃material are better than Zn₂Sn O₄material in pure water.The H₂O₂yields of the two materials at 60 min were 241.606μmol g^-1and137.628μmol g^-1,respectively.However,the increase of piezoelectric properties of Zn₂Sn O₄was significantly higher than that of Zn Sn O₃after the addition of sacrificant（which can make up for the electron hole composite）,and the yield of H₂O₂of Zn₂Sn O₄and Zn Sn O₃were 575.013μmol g^-1and678.086μmol g^-1at 60 min.The reason is that the specific surface area of the former is larger than that of the latter.After the obstruction of electron-hole is excluded,there will be a larger reaction interface under the piezoelectric condition,and the migration rate of electrons from the interior to the outer surface is also greater than that of the latter.This paper also explores the piezoelectric catalytic mechanism of the two materials through quenching experiment.The mechanism of the two materials is the same:the material generates holes and electrons under ultrasonic conditions,and the electrons migrate from the interior to the surface.After arriving at the surface,they combine with oxygen to form peroxyradical,and then combine with electrons and hydrogen ions to form hydrogen peroxide.（2）Two-dimensional Zn Sn O₃material was prepared by coprecipitation method,and the piezoelectric properties of this material were compared with three-dimensional Zn Sn O₃material.The results showed that the performance of two-dimensional materials was better than that of three-dimensional materials,and the yields of the two materials were 695.460μmol g^-1and575.013μmol g^-1,respectively,after 60 min in 10%ethanol solution.The reason is that the total potential of piezoelectric materials is the sum of dipole moments produced by all units along the stress direction of the crystal structure.The greater the surface dimension in this direction,the greater the potential,the greater the polarization of piezoelectric materials is also related to the degree of deformation,which determines the relative positions of positive and negative charges in the crystal.The greater the deformation,the higher the potential and activity of the material.Two-dimensional materials are more likely to undergo bending,or piezoelectric deformation,under external stress,which is more likely to generate a larger piezoelectric potential,so the piezoelectric properties of two-dimensional materials are better.In this paper,Zn Sn O₃and Zn₂Sn O₄are innovatively modified based on the piezoelectric advantage of two-dimensional materials.The two materials are combined by ice bath calcination method.Zn Sn O₃material is taken as two-dimensional template,Zn₂Sn O₄material and a small amount of Zn O and Sn O₂are embedded on the template to form a composite material.After instrument characterization and piezoelectric testing,it is concluded that compared with other piezoelectric materials in this paper,this material has smaller electron-hole recombination ratio,smaller AC impedance value,wider reaction interface,narrower material band gap,valence band and conduction band are more negative,so the piezoelectric performance is the best.This paper also studies the changes of piezoelectric properties under different experimental conditions.Through comparison of several groups of experiments,it is concluded that the properties of materials increase with the increase of ultrasonic frequency,power and liquid disturbance degree,which conforms to the theoretical formula of piezoelectric catalysis.However,too high ultrasonic frequency and power will lead to the decomposition of H₂O₂,thus affecting the piezoelectric catalytic efficiency of materials.At the same time,the acidity and basicity of the solution also affect the properties of the materials.Acidic conditions promote catalysis,while alkaline conditions inhibit catalysis.The reason is that H⁺is involved in the piezoelectric catalytic mechanism of the materials,and H⁺in the solution also promotes the internal electron migration to the surface.This paper provides some piezoelectric mechanism exploration and experimental data for the production of H₂O₂from lead-free piezoelectric materials.At the same time,a new piezoelectric catalytic material with high efficiency is synthesized to explore the small-scale production of H₂O₂in a green way.