Preparation And Photocatalytic Properties Of Niobate-based Photocatalysts

At present,with the rapid development of science and technology,the speeding up of city industrialization,people’s living standard is increasing,but then also produced more and more environmental problems.The water pollution problems directly affect the people’s real life,caused the wide attention from people.How to effectively deal with water pollution problems,protect the earth the already scarce water environment becomes the hot topic of scientific research workers.Semiconductor photocatalytic technology as a kind of green environmental protection technology to remove the organic pollutants,has great application prospect in environmental pollution.However,most semiconductor photocatalytic materials with the problem of light response range narrow,electron hole recombination rate is high,the low utilization ratio of visible light that still a bottleneck.Therefore,looking for new-type high efficiency visible light catalytic material system become inevitable trend.Recently,the constructions of internal or external electric fields make it possible that boost the separation of photoinduced charges.As is well known,ferroelectric crystal possesses spontaneous polarization potential under the stimulation of ultrasound,then an external electric field can be created outside the ferroelectric.Perovskite ferroelectric and piezoelectric niobate unique performance,under the drive of ultrasonic wave,using its unique piezoelectric performance of an electric field can be built,thus improve the photocatalytic performance.In this thesis,series of niobate based composite photocatalysts with high photocatalytic performances were synthesized through hydrothermal and solid phase material method.This thesis mainly includes the following several aspects of research:（1）NaNbO₃ was synthesized by hydrothermal method.Compared with other methods,hydrothermal method has some advantages,such as particles of high purity,good dispersion,easy to control and low cost.Ag₂O/NaNbO₃ composite was successfully prepared by chemical precipitation method.The enhanced photodegradation performance Ag₂O/NaNbO₃ can be attributed to the efficient separation of photogenerated electrons and holes.（2）Series of K_xNa_1-xNbO₃ photocatalysts was synthesized by one-pot hydrothermal method.K_0.5Na_0.5NbO₃（KNN）can be synthesized in alkaline solution with molar ratio of NaOH to KOH 1:5.Through constructing Ag₂O and KNN heterojunction,the utilization of sunlight and photoactivity are enhanced.Moreover,under the effect of ultrasound,the external electric field is constructed,which further promotes the effective separation of photonic electron and cavity,and greatly improves the photocatalytic performance.（3）KNN materials were prepared by using traditional high temperature solid-phase sintering method.Ag₂O/KNN composites show improved visible light harvesting compared with the pure KNN materials,realized the efficient utilization of sunlight.In addition,the separation efficiency of electron hole was improved by constructing Ag₂O and KNN heterojunction,which further improved the photocatalytic performance.