الفهرس 
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Abstract
Numerous ZnO nanostructures, including nanodiscs (NDs), nanorods (NRs), nanorods/nanodiscs (NRs/NDs), and gold nanoparticles (Au NPs)/ZnO NRs, have been produced to improve the photoelectrochemical (PEC) water splitting. The sequential ionic-layer for adsorption and reaction (SILAR) method along with chemical bath for deposition (CBD) at varying deposition periods were used to fabricate the ZnO nanostructures. Different approaches for investigating the structural, chemical composition, optical features, and nanomorphological have been used. SEM study demonstrates that the top surface of ZnO nanostructures morphology varied from nanorods to nanodiscs when the deposition period of CBD was increased from 2 to 12 h. Each film displays polycrystalline hexagonal structure ZnO with a favored orientation (002). As the deposition interval increases from 2 to 12 h, the crystallite size along (002) increases from 40.13 to 175.34 nm. Afterward the Au sputtering period was optimized to 4 minutes, the bandgap of ZnO nanorods was modified from 3.19 eV to 2.13 eV. The photoelectrochemical (PEC) efficiency of the nanostructures was enhanced by controlling the time growth of ZnO and the time of Au sputtering. The 2 h ZnO NRs had the highest photocurrent density (Jph) of all the ZnO nanostructures under investigation. The photocurrent density (Jph) was 7.7 mA.cm-2 of Au/ZnO @4 min which almost 50 times higher than pure ZnO NRs. The greatest ABPE and IPCE values are 2.05% and 14.2%, respectively, at wavelength 490 nm, that is close to the wavelength of Au plasmonic peak absorption. Increased the absorption of visible light region and minority charge carriers, improved photochemical stability reaction, and accelerated electron transfer from the ZnO NRs to the electrolyte carriers are just a few of the significant ways loading Au nanoparticles to pure ZnO might increase photoelectrochemical efficiency.
In this study, a p-n TiO2/NiO nanocomposite based on NiO nanoparticles (NPs) and TiO2 nanotubes (NTs) was created and tuned to enhance the photocatalytic efficacy of methylene blue (MB). TiO2/NiO nanocomposites have been fabricated using the hydrothermal process in the weight ratios 1TiO2/1NiO, 1TiO2/2NiO, and 1TiO2/3NiO. Different analysis devices have been used to investigate the crystal phase, chemical conformation, morphology, and optical characteristics of TiO2/NiO. According to the structural study, NiO NPs, and TiO2 NTs have a cubic, and a monoclinic phase structure, respectively. The bandgap of TiO2 nanotubes lowered from 3.5 to 2.6 eV after the loading NiO nanoparticles ratio was controlled. TiO2/NiO nanocomposites had the highest photodegradation efficacy. The effectiveness degradation of MB dye employing TiO2/2NiO reaches 99.5% within 45 minutes of solar light irradiation compared to 73% with pure TiO2 NTs. Additionally, even after five reusability cycles, the catalytic photodegradation efficiency did not significantly decline, indicating the strong stability of TiO2/2NiO nanocomposite. According to this, loading NiO NP into TiO2 may reduce the recombination of light-generated electron-hole (e-/h+) pairs and increase the range of sunlight spectrum response, both of which lead to increased photocatalytic efficiency. For the photodegradation of MB, the charge motivation mechanisms, and models of kinetic in the TiO2/NiO were addressed. The thesis follows the following format:
Chapter one gives a general introduction to Energy problems and their importance. Hydrogen production methods are also considered. In addition, Photoelectrochemical (PEC) water splitting, and terms are discussed such as photocatalysis, photocathode, Photoanode, PEC setup, and its measurement methods. Water pollution problems, the photocatalytic mechanism, and the parameters for a photocatalytic process are also discussed in this chapter.
Chapter two agreements with the growth of nanostructured ZnO films at low temperatures on glass as a substrate by mixing SILAR method and CBD technique. The mechanism of occurred reaction for ZnO microstructures growth is studied. gold was covered on ZnO by DC sputtering device with different thicknesses to enhance ZnO optical properties. Morphologies, Structures, Chemical composition, and the optical analysis of the manufactured samples have been approached by SEM, XRD, EDAX, and UV/Vis. Spectrophotometer device. In addition, the fabricated samples were studied as a catalyst for PEC Hydrogen production by using OrigaFlex potentiostat in the three-electrodes system.
Chapter three presents the hydrothermal technique to fabricate TiO2 nanotubes (NTs), NiO nanoparticles (NPs), and TiO2/NiO nanocomposite as a powder. These samples were designed and optimized to enhance the photo degradation efficacy of Methylene blue. The structural, optical, and chemical configuration of the fabricated nanocomposites were described by SEM, EDX, UV-Vis, XRD, and FT-IR. The photocatalytic performances of the nanopowders were studied by using MB dye under sunlight and a 400W Xenon lamp. The photodegradation process’s stability, mechanism, and kinetics are studied.
Chapter four presents the final conclusion of this work, the futured plan work, and the Arabic summary.
Keywords:
ZnO nanostructures; Water splitting; Au Surface plasmonic; heterojunction; Photoelectrochemical; TiO2/NiO nanocomposite; photocatalytic; dye degradation.