| With the energy and environmental crisis becoming more and more serious,the use of new technologies to deal with pollution problems and develop new renewable energy is an urgent problem in the field of energy and environment research.In the field of new energy,Fujishima and Hond have successfully used TiO2 to carry out the experiment of producing hydrogen from water by photoelectrolysis in the 1970s.This method of successfully converting light energy into clean chemical energy and storing it is considered as a milestone in the history of photoelectrochemistry.This experiment stimulated the research upsurge of using semiconductors to convert solar energy into hydrogen energy.The efficiency of photocatalytic hydrogen production mainly depends on the properties of photocatalysts.The high recombination rate of carriers is the inherent characteristic of almost all semiconductor materials,which is one of the main reasons for low photon utilization and poor hydrogen production in the photocatalytic process.Therefore,designing a heterojunction structure to induce electrons and holes to migrate in different directions to improve the photocatalytic efficiency has become the most important research direction in the field of photocatalysis.In addition,in terms of environmental crisis,especially a large number of industrial dye pollution has brought great trouble to people's normal life.Therefore,it is an important way to solve the problem of environmental pollution by choosing an efficient and environmentally friendly dye degradation method.As an effective method to degrade or mineralize organic pollutants,advanced oxidation process(AOPs)was proposed by Glaze in 1987.AOPs include ultrasonic catalytic decomposition,photocatalysis,radiation decomposition,UV/O3,UV/H2O2,Fenton,photo Fenton and so on.Compared with traditional AOPs,acoustic catalytic decomposition technology has attracted more and more attention due to its environmentally friendly and convenient operation.The sonocatalytic decomposition of organic dyes mainly depends on the oxidation radicals produced in the cavitation process caused by ultrasound.Therefore,enhancing cavitation is the most effective way to improve the efficiency of ultrasonic catalytic.SrTiO3,as a typical ABO3 perovskite material,has many excellent physical and chemical properties,such as adjustable composition,stable structure,and so on.In particular,SrTiO3 can still maintain good catalytic stability under the extreme conditions of ultrasound,which makes it have a good application prospect in the field of energy and environment.The author used SrTiO3 as the bulk material to study element doping and surface modification.Through the discussion on the composition,lattice structure,bandgap structure,surface microstructure,interfacial hydrophilicity,and electronic structure of SrTiO3,the author revealed the mechanism of oxidation free radicals in the process of ultrasonic catalysis and the methods to improve the efficiency of photocatalytic decomposition of water.This paper is mainly divided into the following parts to discuss.The first part is the introduction of the research background and literature review.Firstly,the author introduces the basic principle of photocatalytic research,the research of new photocatalytic materials,and the design of the new photocatalytic structure.Secondly,the author discusses the structural characteristics of perovskite materials and the current research progress of catalysis.Finally,the author discusses the catalytic advantages and possible research directions of SrTiO3 materials.In the second part,in the process of sample synthesis,the author used the amphiphilic polymer polyethylene oxide-propylene oxide-polyethylene oxide(P123)as the template,and finally synthesized SrTiO3 nanoparticles coated with P123.After coating P123,the hydrophilicity of the sample is greatly improved.The improvement of surface wettability is conducive to the dispersion of the sample in the solution,which reduces the adsorption energy of water molecules and accelerates the reaction frequency of carriers and water molecules.At the same time,the improvement of surface wettability is beneficial to reduce the adsorption energy of water molecules,which speeds up the frequency at which carriers react with water molecules.As a result,photocatalytic hydrogen production of P123@SrTiO3 reaches as high as 402?mol·g-1·h-1 in the absence of any cocatalyst,which is 31 times that of pure SrTiO3.However,the specific surface area of P123@SrTiO3 is only 5.2 times that of SrTiO3.This method can not only improve the photocatalytic efficiency but also improve the surface stability of the samples by using the hydrophilic polymer groups to directional migration of holes.The construction of surface hydrophilic heterojunction provides a new idea for the design of photocatalytic materials.In the third part,to quickly consume the holes and inhibit the recombination of carriers,precious metal and sacrificial reagents such as ethylene glycol(EG)are usually necessary for photocatalysis generation of hydrogen from water.However,the use of precious metals and sacrificial reagents can cause serious environmental pollution.In this work,ethylene glycol(EG)molecule,which was chemically anchored on SrTiO3 nanoparticles(EG@STO)via an in-situ process,was used as a co-catalyst for the first time.The first-principle calculation shows that the EG molecule chemically anchored on SrTiO3 is beneficial to the directional migration of carriers and accelerates the hydrogen evolution reaction.The photocatalytic hydrogen generation efficiency of 237?mol·g-1·h-1 was achieved with EG@STO,which is 19.5 times compared to that of SrTiO3.Moreover,EG@STO remained stable after 32 hours of reaction,in other words,the EG molecule is designed as a new type of efficient and stable co-catalyst,which provides an alternative approach for better semiconductor photocatalytic hydrogen reduction.In the fourth part,carbon-coated SrTiO3(C@STO)was synthesized by in-situ carbonization.Over the years,the element doping and surface heterostructure construction are effective methods to expand the spectral absorption range of semiconductors in the photocatalytic process.However,the internal defects and interface depletion layers caused by these methods will limit the photocatalytic reaction rate.The carbonization of organic matter on the surface of SrTiO3 has greatly improved the surface conductivity and a direct charge transfer between the carbon layer and SrTiO3 was achieved.A 440 ?mol g-1·h-1 and 45 ?mol g-1·h-1 photocatalytic hydrogen production was achieved by C@STO in UV-visible and visible light,respectively.And the visible light catalytic effect was still maintained after 24 hours of reaction.Synchrotron radiation X-ray absorption near edge structure(XANES)and XRD proved the catalytic stability of the sample.This in situ carbonization method provides a new idea for enhancing photocatalytic efficiency and realizing visible light catalysis of wideband gap semiconductor.The fifth part introduces that the acoustic method is more suitable for water treatment than the traditional catalytic method.However,the practical application is limited by the low degradation rate.In this work,the Cr doped SrTiO3 was prepared by a hydrothermal method,and its sonolysis degradation performance was studied.The Cr-doping results in the rough surface due to the decreased crystal symmetry,which increases the surface oxygen adsorption and promotes the cavitation.The optimized Cr-doped SrTiO3 can degrade 95.4%Rhodamine B(5mg/L)in 10 minutes under ultrasound irradiation(53 kHz,350W).The role of hydroxyl radicals in the degradation process has been systematically verified.Furthermore,the sonolysis degradation improvement with the Cr doped SrTiO3 is universal for dyes such as Methyl Blue(MB),Methyl Orange(MO),and Rhodamine B(RhB).This work indicates that the incorporation of finely modified inorganic particles is effective for efficient water treatment.The sixth part is the summary of the paper and the future research prospects. |
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