الفهرس 
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Abstract
Water is a crucial supply for a variety of human applications. It is necessary for the expansion of agriculture and industry as well as for supporting expanding populations that need a consistent source of clean water. History of humanity demonstrates the close relationship between water and human civilization, maybe the best illustration of this impact is Egypt’s Nile River, which supplies nutrient-rich mud and water for agriculture. According to the Human Development Report (HDR), there are three levels of water demand: stress, scarcity, and crisis. According to a recent study, about 5 billion people live in regions where there are hazards to water security. Clean water shortage caused by population increase, industrial revolution and climate change is a serious issue that requires immediate attention. Water and energy are equally essential for achieving high levels of life because they provide the reasons behind all human activities. Fossil fuels (coal, petroleum, and natural gas) mostly provide the present energy demand. Energy security and environmental sustainability are seriously threatened by the continued usage of these fuels and their degrading quality. Nowadays, energy demand is rising quickly as a result of industrialization and the increase in the global population. Then, resolving the conflict between energy consumption and water purification becomes a vital case for the production of freshwater. There are several techniques to obtain fresh water for daily usage, including wastewater treatment, atmospheric water collection and saltwater desalination (SD). Given that the oceans contain over 98% of all the water on Earth using saltwater desalination to produce fresh water makes sense given that marine waters are an endless source of water. SD can be broadly divided into three categories: interfacial solar steam generation (ISSG), membrane-based desalination (MBD), and thermal distillation (TD). For desalination procedures to successfully separate salts from seawater, an enormous quantity of energy is needed. Thermal desalination facilities need 40 to 80 kWh m-3 plus an extra electrical energy of 2.5 to 5 kWh m-3 is required for basic heating. Solar energy is clean, renewable and available richly on Earth which is an excellent candidate for seawater desalination at low-cost. Due to enormous heat loss, the classic method to produce steam heat water based on solar power exhibits low efficiency of photothermal conversion. Solar steam generation by interfacial evaporation is a highly effective and environmentally friendly approach for desalination systems and drinking water purification, which can fully absorb solar energy Interfacial solar evaporation has been recorded using a wide range of materials, designs, and applications. In the last four decades, the field of heterogeneous photocatalysis has expanded rapidly, having undergone various developments, especially concerning energy and the environment. It can be defined as the acceleration of a photoreaction in the presence of a catalyst. The two most significant applications of photocatalysis have been in solar water splitting and the purification of air and water containing low concentrations of pollutants. The multidisciplinary nature of the field has also increased significantly and includes semiconductor physics, surface sciences, photo and physical chemistry, materials science and chemical engineering. In recent years, interest in photocatalysis has focused on the use of semiconductor materials as photocatalysts for the removal of ambient concentrations of organic and inorganic species from aqueous or gas phase systems in environmental clean-up, drinking water treatment, industrial and health applications. This is because of the ability of TiO2 and ZnO nanoparticles to oxidize organic and inorganic substrates in air and water through redox processes.This thesis aims to prepare photothermal devices based on three main components including black material, salt rejector and semiconductor nanoparticles. The black material was synthesized from the pyrolysis of corn cobs powder under nitrogen atmosphere. The resulting black powder shows excellent performance in solar steam generation under the illumination of one sun. The efficiency of biochar was enhanced by semiconductors like TiO2 and ZnO. The challenge here is how to enhance the production of steam from seawater using white metal oxides that may decrease solar absorptivity.The conversion of white semiconductors to darker color is the best solution to increase the percentage of solar absorbance. Additionally, the creation of oxygen vacancies through different reduction methods was applied to generate black titanium and zinc oxides. To prevent salt accumulation on the photothermal devices, PVDF was coated the KT pieces. The research in this study was divided into two projects, the first based on black TiO2 and the other on reduced ZnO. Structural of the prepared samples was determined using TEM, SEM, elemental mapping, XRD, FTIR, UV/vis spectroscopy, thermal conductivity and XPS analysis. The analysis results exhibited the nanocomposites were successfully prepared.For the first project, the manufactured photothermal was richly porous, had high hydrophilicity, low thermal conductivity and effectively absorbed a wide range of the sun spectrum. Black titania (BT was prepared by the molten salt method in the presence of Al metal during the reduction process. Four ISSGs were prepared and the steam generation experiments were conducted under the same conditions. AgCu@BT/BC on KT served as the substrate and water molecule transfer channel, while nanocomposites operated as a photothermal layer with exceptionally high solar absorption. Under one sun illumination, the AgCu@BT/BC photothermal device exhibited an excellent evaporation flux of 1.4 kg m-2 h-1 with a conversion efficiencyof 95.7%. Additionally, the fabricated system demonstrated long-term reliability, strong desalination efficiency, and superior salt rejection. Significantly, the total amount of Na+ during desalination using AgCu@BT/BC was lower than the WHO drinking water criteria, allowing the nanocomposite to be used for both wastewater treatment and saltwater desalination. Additionally, the prepared nanocomposites were investigated for the photocatalytic degradation of some organic pollutants. AgCu@BT/BC exhibited complete degradation of MO dye after 150 min in an acidic medium. In the second project, the white ZnO was prepared by sol-gel method followed by calcination at 550 °C in a muffle furnace. The fabricated white ZnO was converted into a darker color using sodium metal in an evacuated Pyrex bottle to produce reduced ZnO (RZ). The photothermal efficiency of RZ was enhanced by incorporating BC to increase the blackness of the nanocomposite. Plasmonic metals like Ag and Cu were loaded on the surface of RZ/BC to increase the surface temperature. Furthermore, AgCu@RZ/BC exhibited the highest evaporation flux of 1.8 kg m-2 h-1compared to other prepared photothermal systems under illumination of one sun. The density of localized hotspots on the surface of the photothermal system increased by the incorporation of AgCu core-shell that promotes photothermal activity and improves the photocatalytic activity of methylene blue dye degradation. Assemblages of AgCu nanoparticles on the surface of RZ generated a strong stochastic plasmonic coupling and therefore broad-band absorption for much better solar energy consumption. The AgCu@RZ/BC nanocomposite exhibited an excellent vaporization flux of 1.8 kg m-2 h-1 with high efficiency reaching 98% under the illumination of one sun. AgCu@RZ/BC exhibited an excellent surface temperature of 41 °C after only 5 min compared to other prepared photothermal systems. Furthermore, the prepared composites revealed superb photocatalytic degradation of MB dye under UV-vis light with complete degradation. The band gap energy of ZnO decreased from 3.1 eV to 2.46 eV in the case of AgCu@RZ/BC nanocomposite.For further analysis, the photoelectrochemical measurements were applied using i-t plots, EIS and Mott-Schottky techniques in the presence and absence of light. Due to the numerous benefits of the fabricated device including superior performance, cost-effectiveness, all-weather use, and extensible fabrication, our integrated design holds promise for the fabrication of large-scale solar-powered steam for producing clean water. Moreover, the crystalline AgCu@BT/BC and AgCu@RZ/BC demonstrate outstanding photocatalytic performance because of boosted charge migration, reduced electron-hole pair recombination rate, and identifiable shift to the red region.