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Studies on the Preparation and Photocatalytic Aactivity of New Zinc Oxide Based Photocatalyst

Author: ZuoKe
Tutor: MaHongChao
School: Dalian University of Technology
Course: Environmental Science
Keywords: doped ZnO photocatalysis L-cysteine
CLC: TQ426
Type: Master's thesis
Year: 2012
Downloads: 2
Quote: 0
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Abstract


Zinc oxide is a promising semiconductor material owing to its advantages,such as excelent chemical, physical properties,environmental stability and low synthesis cost. But the ZnO has its limitations,such as severe agglomerates,dispersion of particles,easy to produce light corrosionand.ZnO could be only activated by UV light.Therefore,study of a new modified ZnO photocatalytic materials which has simple efficient and solar utilization is very important.We chose a small peptide molecule L-cysteine as a common source of C,N,ands.In this study,C-N-S-triped ZnO nanocrystals were synthesized by using microwave hydrothermal m-ethod,hydrothermal method and calcination method. The photocatalysts were characterized by X-ray diffraction (XRD),UV-Vis diffuse reflectance spectroscopy (UV-vis),fluorescence spectra,X-ray photoelectron spectroscopy (XPS).The effects of preparation conditions and the doping amount were investigated in thestudy. Also discusses the interaction of C,N,andS doping modification and photocatalytic performance of ZnO.In this experiment, the main contents and conclusions are as follows:(1) Mcrowave hydrothermal method;The XRD pattern shows that the samples containing the ZnO crystal. UV-vis showed that doped samplesenhanced on visible light absorption. XPS showed the sample surface containing C, N, S element. Zinc carbon in a molar ratio of2:1,the microwave power800W for1min can get ZnO photocatalyst catalytic performance. When its dosage is0.25g/L, C-N-S-triped ZnO demonstrates decolorized rate of94%for lOmg/L reactive brilliant blue solution on UV light. However,demonstrates decolorized rate of28.04%for reactive brilliant blue solution under Xeon lamp irradiation for120min.(2) Hydrothermal method;The XRD pattern shows that the samples containing the ZnO and the ZnS crystal. UV-vis showed that doped samplesenhanced on visible light absorption. XPS showed the sample surface containing C, N, S element. Zinc carbon molar ratio of1:2,C-N-S-triped ZnO keeped at160℃for36h demonstrates decolorized rate of45%for1Omg/L reactive brilliant blue solution under Xeon lamp irradiation. While zinc carbon in a molar ratio of8:1,zinc carbon keeped at180℃for36h demonstrates decolorized rate of72.13%under UV light.(3)Calcination method; The XRD pattern shows that the samples containing the ZnO crystal. UV-vis showed that doped samplesenhanced on visible light absorption. XPS showed the sample surface containing C, N, S element. Zinc carbon molar ratio of1: l,C-N-S-triped ZnO calcined at400℃for2h, The best degradation rate reaches63.9%under UV light and37%under Xeon lamp irradiation. Comparing with undoped ZnO,the catalytic properties of doped samlpes are slightly improved under the UV light and xenon lamp. The light absorbing performance shows that sample for ultraviolet and visible absorption significantly are enhanced.In conclusion,C-N-S tridoped ZnO nanocrytals were synthesized by using L-cysteine. The tridoped sample enhanced and extended the photocatalytic activity in the UV and visible-light region, and also reducded light induced electron recombination rate, making ZnO photocatalytic activity could be improved effectively.

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