Study On The Synthesis,Modification And Photocatalytic Properties Of ZnO Prepared By Hydrothermal Method With Different Morphologies

With the development of industrial economy and the improvement of people's living standards,more and more attentions are paid to the environmental issues,especially the water pollution.Catalysts operating effectively under visible light irradiation are applied to deal with the environmental problems,which has attracted most of researchers' attentions.In this paper,we firstly synthesized three kinds of ZnO catalysts with different morphologies hydrothermal method,including flower,rod and spherical.CdS quantum dots(QDs)were synthesized by water phase method and used to sensitize spherical ZnO catalyst(CdS/ZnO).Secondly,high efficiency nonmetal-doped ZnO:B and ZnO:C photocatalysts were synthesized through the hydrothermal method.Finally,properties of the obtained samples were characterized by X ray powder diffraction(XRD),scanning electron microscopy(SEM),energy spectrum analysis(EDS)and ultraviolet visible spectrophotometer(UV-vis)and so on.The photocatalytic performance of the samples were analyzed by photodegradation of methyl orange solution.The main results are as follows:(1)ZnO photocatalyst with shapes of flower,rod and sphere were synthesized by hydrothermal method under different operation conditions.The results showed that the spherical ZnO photocatalyst has the best photocatalytic activity and its degradation rate is 27.8%,which is 1.56 and 3.8 times faster than the flower-like and rod-like ZnO,respectively.(2)CdS/ZnO composite photocatalyst was obtained by using the CdS QDs to sensitize spherical ZnO,and the effects of sensitization time and temperature on the catalytic performance of the CdS/ZnO photocatalyst were investigated.Results show that CdS/ZnO photocatalyst exhibits the best photo-catalytic activity when the sensitization time is 2h at room temperature and the sensitization time is 2 h at 60 ?.The degradation efficiency for the two conditions are 39.5%and 41.4%,respectively,which are 1.54 and 2.09 times compared with the pure ZnO.(3)B-doped spherical ZnO photocatalyst was successfully prepared by hydrothermal method.The effect of different concentrations of B on the photocatalytic properties of the spherical ZnO was investigated,and the optimum concentration of the nonmetal B-doped spherical ZnO was 0.7%.When the doping amount of boron was 0.7%,ZnO:B photocatalyst has the best photocatalytic activity.Photocatalytic degradation rate of methyl orange can reach 81.5%,which is 1.83 times compared with pure ZnO(44.6%).(4)C-doped ZnO photocatalyst was prepared by hydrothermal calcination two step method.The effect of C-doped concentrations on the photocatalytic activity of ZnO and the mechanism of its photocatalytic degradation were studied.When the C content was 9%,the as-prepared samples showed the best photo-catalytic performance.This result was attributed to the restriction on the recombination of electron-hole pairs and the reduction of energy bandgap of ZnO,enhancing the absorption ability of C-ZnO catalyst in visible light region.The highest degradation efficiency can reach 90.5%when C-ZnO catalyst was used to photo-degradation methyl orange within 3h,which was 2.12 times higher than that of the original ZnO(42.6%).The photo-degradation can be well fitted with the pseudo-first order kinetics reaction.9%C-doped ZnO had the maximum degradation rate,which is 6.3 times higher than the original ZnO.