الفهرس | Only 14 pages are availabe for public view |
Abstract The objective of this thesis was to produce novel materials possessing promising characteristics suitable for applications in photocatalysis and optoelectronics. The study employed three distinct synthesis techniques, namely co-precipitation, sol-gel, and auto- combustion, to produce pure and mono-doped bismuth oxide (Bi2O3) and bismuth ferrite (BiFeO3). The investigation encompassed an analysis of the influence of synthesis methods, the choice of precipitation agents, and the effect of doping with various metals. The resulting oxides were subjected to a comprehensive examination utilizing techniques such as X- ray diffraction, scanning electron microscopy with energy-dispersive X- ray analysis (SEM-EDX), transmission electron microscopy, Fourier- transform infrared spectroscopy, diffuse reflectance (DR), and UV-Vis spectroscopy. The photocatalytic performance of the synthesized oxides was assessed through the degradation of dyes (Congo red and Methylene Blue) under visible light. The thesis is structured into three main chapters, which are summarized as follows: The first chapter (Introduction): This chapter composed of two sections: The first section presented a general overview on metal oxide semiconductors MOS, their properties, and their potential applications. It emphasizes solar light photocatalysis and photocatalytic applications of metal oxides semiconductors. It provides insights on routes followed to enhance their efficiency. It throws light also on the dielectric English Summary 132 characteristics of MOS and investigates the effect of doping on their properties. The second section provided a literature review of recent studies on metal oxides under study; bismuth oxide (Bi2O3) and bismuth ferrites (BiFeO3). It also investigated the effect of doping specific metal ions on the properties of these metal oxides and these modifications were explored in terms of their impact on their structural, electrical, optical, and photocatalytic properties. The second chapter (Experimental): This chapter provided a comprehensive description of the chemicals and the synthetic procedures employed to create the nanostructured metal oxides under study. Firstly, the co-precipitation method was utilized for the synthesis of undoped Bi2O3 materials using different precipitating agents: NaOH, KOH and NH4OH. The precipitation process was followed by a calcination step at 500 °C. Secondly, the sol-gel technique was employed to fabricate pure Bi2O3, as well as In, Cu, and Li-doped Bi2O3 photocatalysts optimized for visible-light-driven applications. The third class of materials under investigation included pure and doped bismuth ferrite compositions, namely pure BiFeO3 and Ce-doped-BiFeO3/Bi25FeO40 were prepared successfully through the auto-combustion method. The chapter further outlines the procedures employed to assess the photocatalytic activity of these oxides by degrading organic dyes. |