Modification Of Nano Zinc Oxide And Study On Photocatalytic Activity

Semiconductor photocatalysts have attracted much attention due to their low energy consumption,mild reaction conditions,simple operation flow,no secondary pollution,and especially the ability to effectively degrade organic pollutants that are difficult to biochemically and highly biotoxic.The zinc oxide(ZnO)semiconductor is a direct bandgap(3.36 eV)n-type semiconductor material with a large exciton binding energy(60 meV).Although ZnO nanomaterials have many photocatalyst advantages,their higher photogenerated carrier recombination rate and narrower spectral absorption range limit their application in photocatalysis.Therefore,.limiting the recombination of photo-generated carriers in ZnO nanomaterials and broadening the spectral absorption range of ZnO is an effective way to improve its photocatalytic performance.This paper improved the dispersibility of nanoparticles by water-soluble polymer combined with vacuum freeze-drying technology.The advantage of this method is that the process is simple,no organic solvent is used,the raw materials are cheap and easy to obtain,and the prepared nanoparticles are uniformly dispersed.There is a Schottky barrier at the heterojunction structure formed by the interface between the noble metal Ag and ZnO,which promotes the separation efficiency of photogenerated electrons and holes.By using noble metal loading modification methods,Ag nanoparticles are used as electron absorption enthalpy,which promotes more electron separation by capturing photogenerated electrons and prolongs the time of photogenerated carrier recombination;at the same time,more photogenerated holes are converted into hydroxyl groups.Free radicals accelerate the efficiency of photocatalytic degradation of dyes.The structural morphology and optical properties of Ag-ZnO samples were characterized by a series of methods.The calcination temperature of the precursors was determined by TGA-DTG.The photocatalytic degradation experiments show that the Ag-ZnO photocatalyst has better effect on degradation of methyl orange(MO)and methylene blue(MB)under the same conditions.Further loading graphene on the surface of Ag-ZnO not only increases the specific surface area of the composite,but also allows more dye molecules to be adsorbed,which is beneficial to concentrated photocatalytic degradation,and graphene can also capture photogenerated electrons in the ZnO conduction band,shrink the band gap of ZnO and increases the photocatalytic efficiency.Besides,adhering the inorganic nanoparticles to the surface of the two-dimensional graphene sheet structure can avoid the agglomeration of the graphene sheet structure and increase the stability of the composite material.The structural morphology and optical properties of Ag-ZnO-rGO photocatalysts were characterized by a series of means.The photocatalytic degradation experiments of MO show that Ag-ZnO-rGO composites exhibit excellent adsorption and photocatalytic activity in the dark and ultraviolet,respectively.Finally,the photogenerated electron transfer path and photocatalytic mechanismin of Ag-ZnO-rGO composites are clarified.