Ultrafast Piezo-Photocatalytic Degradation Of Organic Pollutions By Ag₂O/tetrapod-ZnO Nanostructures

In recent years,photocatalysis has been widely concerned in environmental governance and energy development.The development of photocatalytic materials with high photocatalytic efficiency and activity has also been the focus of research at home and abroad.At present,the work is mainly focused on the two aspects:(1)the modification of the common photocatalysts such as TiO2 and ZnO to improve the photocatalytic activity;(2)the development of new photocatalysts.The efficiency of the photocatalysts is closely related to its structure and morphology,thus the design and synthesis of photocatalytic materials with certain structure and morphology according to the actual needs has become the hot research.Among them,ZnO is not only a typical semiconducting material but also a kind of piezoelectric material.Furthermore,it can act as a photocatalyst to photodegrade the organic pollutants.Therefore,combining the piezoelectric effect and photocatalytic performance of ZnO,organic pollutants in wastewater can be actively photodegraded to nontoxic CO2 and H2O.In our group's previous work,we have successfully combined the photocatalytic activity of the ZnO with piezoelectric properties to achieve the piezoelectric-photocatalytic degradation of organic pollutants.However,the efficiency is not high enough.The further study is needed to improve the photocatalytic efficiency of ZnO.In this thesis,the Ag2O/tetrapod-ZnO nanocomposites are synthesized by two simple steps,the nanocomposite was used to prepare a piezoelectric-photocatalytic experimental device,and photocatalytic materials with faster catalytic degradation and better cyclability were obtained.The main contents are as follows:(1)Synthesis of Ag2O/tetrapod-ZnO nanostructures:Tetra-zinc oxide(T-ZnO)nanostructures were prepared in large quantities by thermal evaporation method and Ag2O nanoparticles were uniformly supported on the entire surface of T-ZnO nanostructures.(2)Photocatalytic performance of Ag2O/tetrapod-ZnO nanostructures:Ag2O/T-ZnO nanostructures can efficiently use both mechanical energy and UV energy to rapidly degrade organic pollutants under the combined action of ultrasound and UV irradiation.Taking methylene blue(MB)solution as an example,Ag2O/T-ZnO nanostructures(2 g L-1)can completely degrade MB(5 mg L-1)aqueous solution within 2 mins under ultrasonic(200 W)and ultraviolet(50 W).This rate of degradation is much higher than previous experimental results and has the potential to be used as a wastewater treatment technology at the industrial level.(3)Piezoelectric-photocatalytic mechanism of Ag2O/tetrapod-ZnO nanostructures:In this process,the piezoelectric field of T-ZnO nanostructures and the built-in electric field of Ag2O/T-ZnO heterostructure can separate photogenerated electron-hole pairs,reducing the recombination rate of electron and hole to improve the photocatalytic activity.The current experimental results can promote the development of sewage treatment technology in improving the environment.