Regulation Of Suface Interface Of Piezoelectric Material And Their Piezocatalytic And Piezo-photocatalytic Performance

Piezocatalysis is a very novel technology,in which mechanical energy such as vibration,friction,natural wind and tide inducepiezoelectric potential of piezoelectric materials to drive redox reaction by collecting.In addition,piezoelectric polarization induced by mechanical energy can be used as a flexible automatic valve to regulate the charge transfer pathway and facilitate the separation of photogenerated charges in bulk phase and on the surface of semiconductor.This provides new opportunities for the application in environmental and energy catalysis of piezoelectric materials using mechanical energy and solar energy.However,the construction strategy of high efficiency piezo-photocatalyst needs to be explored,and the key factors influencing the performance of piezocatalyst and piezo-photocatalyst are not clear.Thus,aiming at these key scientific problems,this dissertation focuses on collaborative modulation of the charge separation and active sites to develop the novel coupled-catalysis strategies.This dissertation not only expands the application range of the piezo-photocatalysis,but also clarify and identify the key factors of piezocatalysis and piezo-catalysis.The main research contents and results are as follows:（1）In order to develop a new strategy to improve the performance of piezocatalysis and verify the influence of surface chemical properties of catalysts on catalytic performance,Ba Ti O₃nanobelt featuring controlled oxygen vacancies were prepared to systematically investigate the effect of oxygen vacancies on pizeocatalytic performance for degradation of organic pollutant.The piezocatalytic activity exhibited a volcano-type trend with increasing oxygen vacancies.BTO-OV-1 exhibits a higher degradation rate constant of 0.0253 min^-1,which is twice that of Ba Ti O₃.Results from density functional theoretical（DFT）calculations and O₂-temperature programmed desorption（O₂-TPD）measurement indicated that the presence of oxygen vacancies could efficiently adsorb and activate O₂ on the surface of Ba Ti O₃nanobelt.Piezoresponse force microscopy（PFM）measurement,showed that the introduction of oxygen vacancy would decrease the piezo-potential of Ba Ti O₃,making that the appropriate oxygen vacancy concentration is critical to optimize the piezo-catalytic performance.（2）Empolying piezoelectric effect combined with regulation of active site,a high performance piezo-photocatalyst was constructed to convert benzylamine pollutant into high-value-added organic intermediates.Bi₄Nb O₈Br nanosheet（BNO）oriented along the[001]direction with abundant oxygen vacancies were synthesized by a flux method followed by H₂/Ar thermal treatment.We found that the conversion rates of benzylamine for BNO-OV-2with rich oxygen vacancies under simultaneously light irradiation and mechanical vibration was2.1 times higher than that of pristine BNO under only light irradiation.Photoelectric chemical testing,theory calculation and in situ EPR were used to explore the charge separation of piezo-photocatalysis,and the effect of oxygen vacancy on the adsorption activation of benzene methylamine and O₂ and charge separation.（3）Empolying piezoelectric effect combined with regulation of active site on heterojunction interface,the hierarchical and piezoelectric Z-scheme Ba Ti O₃-Zn In₂S₄heterostructures were dexterously designed and constructed for high efficient co-production of H₂ and C-N coupling products of benzylamine.Theoretical and experimental results demonstrate that the spatial separation of both charge carriers and surface redox regions can improve the separation efficiency of photogenerated charge carriers and lower the energy barrier of surface reaction.（4）g-C₃N₄ with different group was synthesized by molecular engineering,the piezo-photocatalytic H₂O₂ production of synthesized g-C₃N₄modified by phosphorus（CN-P）,oxygen-functionalized g-C₃N₄（CN-OF）,and cyanogroup（CA）grafted g-C₃N₄（CN-CA）were investigated systematically.It is found that the modification of oxygen-containing group and P group can improve the piezocatalytic H₂O₂ production,while the introduction of cyanide group decreases the piezo-catalytic activity.The piezoelectric effect improves the photocatalytic performance of the CN-OF and CN-P by 1.46 times and 1.94 times,respectively,while decreases the pizeo-photocatalytic activity of the CN-CA by 6 times.The order of the energy barrier for H₂O₂ production is-OH（0.69 e V）>P（0.48 e V）>-COOH（0.39 e V）>-C=O（0.35e V）>-CN cyanide group（0.22 e V）.Thus,piezo-photocatalysis requires comprehensive consideration of the multiple effects of the material size,piezo-potential and active site on charge separation and surface reaction in the catalytic process.