The Study Of The Powder Preparation And Its Piezocatalytic And Pizeo-Photocatalytic Effects Of Perovskite Ferroelectric Materials

The contemporary world is facing the environmental contamination and energy shortage problems due to fossil-fuel consumption is steadily increasing,which has become an issue that people are more and more concerned about.Photocatalytic technology can make the best of renewable solar energy to degrade organic pollutants and produce clean fuels.In the realm of photocatalytic semiconductors,the serious recombination of photogenerated electrons and holes normally leads to low photocatalytic activity,which remains a key issue to retard the indus-trial application of photocatalysts.In recent years,due to the structural flexibility of perovskite oxide ferroelectric materials and their piezoelectric and ferroelectric properties,it has been applied in the field of catalysis,and research on its piezocatalysis and pizeo-photocatalysis has led to extensive attention.In this thesis,I mainly focuses on the preparation,composite modification,pizeocatalytic and pizeo-photocatalytic performance of perovskite ferroelectric materials.Mainly two main research contents were carried out:Research on the preparation of BaTiO₃ and BaTiO₃@LaFeO₃ composite powder,and it’s piezocatalysis performance;Study the influence of different Ag particle loading content and piezoelectric effect on the photocatalysis performance of Na_0.5Bi_0.5TiO₃ nanosheets.The main research results as follows:（1）The BaTiO₃@LaFeO₃ composite nanostructure was prepared by hydrothermal method and calcination process,and p-n heterostructure formed by it greatly enhanced the piezocatalytic performance of BaTiO₃ .The BaTiO₃ samples were prepared by hydrothermal method according to different conditions and parameters,research on that the influence of mineralizer NaOH concentration,temperature and holding time on the structure,micro-morphology and piezocatalytic performance of BaTiO₃ .The BaTiO₃ nanocube powder with tetragonal phase and great piezoelectric properties was successfully prepared by hydrothermal method.Innovatively through the hydrothermal method,p-type semiconductor LaFeO₃ nanoparticles were successfully loaded on the surface of n-type semiconductor BaTiO₃ nanocube to obtain BaTiO₃@x mol%LaFeO₃ composite nanostructures.After 80 minutes of sonication,the degradation rate constants of the composite nanostructures with x=5,10,20 and 40 for the MO dye were 16.9×10^-3min^-1、21.9×10^-3min^-1、23.7×10^-3min^-1、36×10^-3min^-1和19.4×10^-3min^-1respectively,the piezocatalytic performance of the BaTiO₃@20mol%LaFeO₃ sample is the best,which is 2.13 times the rate constant of the bulk BaTiO₃ to degrade MO dye.（2）The Na_0.5Bi_0.5TiO₃ nanosheets were prepared by the molten salt method with simple process and low cost,and the Na_0.5Bi_0.5TiO₃@1wt%Ag nanocomposite structure was further prepared.The latter’s pizeo-photocatalytic degradation rate constant of Rh B is as high as 146×10^-3min^-1,which is 7.6 times that of the former.Innovatively combine the piezoelectric effect of Na_0.5Bi_0.5TiO₃ nanosheets with localized surface plasmon resonance（LSPR）effect generated by Na_0.5Bi_0.5TiO₃@Ag,which effectively promotes the separation and transmission of photogenerated carriers of Na_0.5Bi0.₅TiO₃ ,and greatly enhances Na_0.5Bi_0.5TiO₃ catalysis performance.The prepared Na_0.5Bi_0.5TiO₃ nanosheets with complete morphology,good crystallinity and no impurity phases,it’s the length and width are about 2-3μm,and the thickness is about 300nm.The Na_0.5Bi_0.5TiO₃ nanosheets were modified by the photoreduction method to prepare uniformly loaded Na_0.5Bi_0.5TiO₃@Ag nanosheets.Study on the performances of Na_0.5Bi_0.5TiO₃ and Na_0.5Bi_0.5TiO₃@Ag for the degradation of RhB by photocatalysis,piezo-catalysis and piezo-photocatalytic degradation were,and it was concluded that the catalytic degradation effect of Na_0.5Bi_0.5TiO₃@1wt%Ag was the best.At the same time,explaining the mechanism of each catalytic process of Na_0.5Bi_0.5TiO₃@Ag in detail.In a word,this thesis studies the piezocatalytic performance of BaTiO₃ and the piezo-photocatalytic performance of Na_0.5Bi_0.5TiO₃ in detail.Through the method of composite and modification,the piezocatalytic performance of BaTiO₃ and the pizeo-photocatalytic performance of Na_0.5Bi_0.5TiO₃ were successfully improved.It is hoped that the work in this thesis will be helpful to the development of perovskite oxide ferroelectric materials in the field of catalysis.