Porous Zno Nanostructuctures Controllale Fabrications And Photocatalytic Performance Enhancing Mechanism Research

Zinc oxide(ZnO)as a kind of avirulent wide bandgap n-trype semiconductor photocatalyst,has the advantages of high electron mobility and easy preparation.this paper proposes a simple liquid hydrolysis method to prepare porous ZnO nanostructures with high activity surface,nano size and good dispersibility.On this basis,the "structure-activity relationship" between porous ZnO microstructure and photocataly tic performance is revealed.(1)Using liquid phase hydrolysis method,choose ethanol/water as solvent,anhydrous zinc acetate as precursor,the reaction temperature conditions for 55～75℃,through regulating the volume of ethanol and water ratio,can be prepared by the polarity base surface(000(?))and high index(10(?)1)of porous cone-like ZnO mesocrystals.Found combined with density functional theory(000(?))and(10(?)1)crystal plane adsorption for ethanol molecules can more than(0001)and(10(?)0),and(000(?))and(10(?)1)crystal plane of the adsorption of water molecules can be less than(0001)and(10(?)0).Therefore,the water content is easy to form a porous conical structure consisting of(000(?))and(10(?)1).When the water content is high,the product is easy to form dome-like shape consisting of(0001)and(10(?)0).Similarly,after replacing the solvent type,the above morphological evolution law can also be found in DMF/water system.The photocatalytic degradation of methyl orange shows that the photocatalytic properties of the porous cone-like ZnO mesocrystals with three typical morphologies of the nano ZnO photocatalysts(porous cone-like mesocrystals,dome and disc-like nanocrystals)have the best photocatalytic properties.The excellent photocatalytic properties are mainly attributed to:(000(?))and(10(?)1)the "surface junction" constructed on the surface of the crystal is beneficial to the effective separation of photogenerated electrons and holes,and improves the lifetime of the optical carrier.(2)The porous hexagonal ZnO nanoscale with a size of 50nm was successfully prepared by the solution of liquid phase decomposition(liquid-phase decomposition)in the anhydrous zinc acetate/NaOH/ethanol/water system by increasing the concentration of zinc salt and introducing NaOH as precipitant.The porous nanoscale is composed of polar crystal surface(0001),(000(?))and(10(?)0)crystal surface.And(10(?)0)the percentage of bare surface can be controlled by changing the volume ratio of ethanol to water.The photocatalytic degradation of methyl orange showed that nanoineter ZnO three typical morphology(nano porous hexagonal,plates and six prism)photocatalytic effect in porous hexagonal ZnO nanosheets best.The performance enhancement is mainly attributed to the spontaneous polarization electric field between the upper and lower polar surfaces(0001)and(000(?)),and(10(?)0)the smaller the proportion of the bare surface of the crystal,the higher the catalytic performance.(3)By using the liquid hydrolysis method proposed in this paper,the microstructure of nanoscale ZnO can be regulated by changing the volume ratio of water and organic solvents in the system(including the bare crystal surface,size and porosity).The strategy is of important experimental reference and theoretical significance for the development of new oxide functional materials developed by green chemistry.