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Synthesis and Characterization of ZnO Nanostructure, Modified by Graphene and CdS for PEC Application

Nourmohammadi, Mohammad Amin | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44478 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Moshfegh, Alireza
  7. Abstract:
  8. In this project, the photoelectrochemical properties of ZnO nanostructures modified by CdS and Graphene was studied. Firs, titanium foil was cut into rectangular shape with 1cm width and 3 cm length, cleaned by rinsing in acetone and ethanol and annealed at 4000C for an hour. As a result, a thin layer of titanium oxide was formed on Ti sheet. Then a layer of grapheme oxide was deposited on substrate using Electrophoretic deposition (EPD). After that, ZnO nanostructure was deposited on the TiO2 substrate using Electropulsation (EP) with 20 consecutive pulse followed by 3 minutes Electrodeposition (ED). Using SEM analysis, the morphology of ZnO was determined to be nanopetals in which the thickness of each petals was about 50 nm. The optical properties of samples were studied using Diffuse Reflection Spectroscopy (DRS) analysis and the ZnO absorption edge was measured about 375 nm. Moreover, according to PEC test result, the photocurrent density generated by ZnO/Graphene/CdS was about 3.5 mA/cm2. In the next step the second graphene layer was deposited on ZnO nanostructure, using the same procedure as the first graphene layer and the sample was annealed at 4000C for 1 hour. Subsequently, CdS quantum dots (QDs) were deposited on sample, using Successive ionic layer adsorption and reaction (SILAR) method with 30 cycles. According to SEM images the estimated size of CdS QDs was about 15 nm. Moreover, the surface chemical composition of the samples were studied using XPS analysis. The final results of PEC test showed a noticeable increase in generated photocurrent density to about 27 mA/cm2 for the CdS/Graphene/ZnO/Graphene/TiO2/Ti nanocomposite system as compared to ZnO/Graphene/TiO2 ones
  9. Keywords:
  10. Zinc Oxide ; Graphene ; Cadmium Sulfide ; Photoelectrochemical Cell ; Electrodeposition

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