Preparation And Performance Of Novel Iron-Based Nanocomposite Material For Photocatalysis

The increasing concern over environmental pollution and its impact on human health and the ecosystem has led to the development of semiconductor photocatalysts.This thesis explores the potential of iron-based semiconductor photocatalysts as a cost-effective and efficient solution for environmental remediation and sustainable development goals.The contamination of water by various sources,including pharmaceutical factories,garment industries,paper and pulp industries,and dye and tannery facilities,among others,poses a significant challenge.Organic pollutants are a significant contributor to water contamination,and conventional treatment methods have proved disadvantages.Photocatalysis offers a cost-effective and efficient alternative by harnessing the power of light to degrade organic pollutants into harmless products.Iron-based semiconductor photocatalysts offer distinctive physicochemical characteristics,such as low cost,high redox potential,and stability,which make them ideal for various environmental and energy applications,such as water purification,hydrogen production,and CO₂ reduction.Recent studies have shown an outstanding photocatalytic ability of supporting iron-based semiconductor material for environmental remediation and water-splitting applications.Among the various iron-based semiconductors,zerovalent iron and iron oxide,supported with graphitic carbon nitride and titanium dioxide,are considered to be more effective and promising materials for a variety of applications.However,the practical use of iron-based semiconductor photocatalyst materials is restricted by poor electrical conductivity,rapid recombination of photogenerated electron-hole pairs,ineffective solar-light absorption,and inadequate visible light responses.Additionally,the limited understanding of the reaction mechanisms and the complex interactions between the photocatalysts and the target pollutants also hinder the optimization and practical application of iron-based semiconductor photocatalysts.These challenges highlight the need for continued research to improve the performance and practical applications of iron-based semiconductor photocatalysts.This thesis aims to explore the potential of iron-based semiconductor photocatalysts as a promising alternative to conventional photocatalysts for environmental remediation and sustainable development properties and their ability to harness solar energy for catalyzing photochemical reactions.Their low cost and easy access to raw materials make them a more accessible option for industries and research communities.This thesis illustrates the fabrication,modification,characterization,and photocatalytic application of zerovalent iron,and its oxide endowed with the mechanical support of graphitic carbon nitride and titanium dioxide,aiming to test and enhance their photocatalytic efficacy.This research studies the relationships among synthetic designs,microscopic/electronic framework,and photocatalytic efficiency,creating different visible-light photocatalysts for the removal of hazardous pollutants.The development of highly conductive,durable,and active low-cost photocatalysts is a crucial step in the treatment of environmental contaminants.The first catalyst investigated in this study employed a facile approach to the fabrication of Fe@Fe₂O₃ core-shell nanoparticles adsorbed on g-C₃N₄ nanosheets through a chemical adsorption process.The resulting Fe@Fe₂O₃/g-C₃N₄ nanocomposites exhibited a unique morphology characterized by a narrow dispersion of Fe@Fe₂O₃ nanostructures uniformly distributed on the g-C₃N₄ nanosheets.The study investigated the impact of varying reaction parameters,such as reaction time and reducing agent concentration,on the reactivity and properties of iron.Notably,it was observed that loosely aggregated particles were formed under a higher addition rate,while nanoclusters were formed upon the slow injection rate of the reducing agent.The enhanced photoactivity of Fe@Fe₂O₃/g-C₃N₄ nanocomposites for RhB and phenol was explored in depth,revealing that the superior photocatalytic efficiency observed（6.0 times greater than pristine g-C₃N₄ and 6.7 times greater than Fe@Fe₂O₃）was due to the heterojunction formed between Fe₂O₃ and g-C₃N₄.This heterojunction facilitated efficient charge partition,thereby reducing electron-hole recombination,and promoting the separation of photogenerated charges.Furthermore,mechanistic insights into the degradation process of the pollutant RhB were gained using Fe@Fe₂O₃/g-C₃N₄ nanocomposites.The quenching test revealed that the main active species involved in the degradation of RhB were the holes（h⁺）and superoxide radicals（.O₂^-）.The holes（h+）were responsible for oxidizing the organic compounds,while the superoxide radicals（.O₂^-）promoted the formation of hydroxyl radicals（.OH）through a Fenton-like reaction,leading to the breakdown of RhB.Overall,this research provides unique mechanistic insights into the degradation process of the pollutant RhB using Fe@Fe₂O₃/g-C₃N₄ nanocomposites and highlights their potential to eliminate contaminants.The second catalyst explored in this research reports the fabrication of TiO₂-decorated Fe₂O₃Q/g-C₃N₄ ternary Z-scheme photocatalyst via low-temperature calcination.The subsequent Fe₂O₃QDs/g-C₃N₄ and TiO₂/Fe₂O₃QDs/g-C₃N₄ were investigated in terms of structure,morphology,optical properties,and surface chemical composition analysis via transmission electron microscopy（TEM）,X-ray photoelectron spectroscopy（XPS）,energy dispersive x-ray spectroscopy（EDX）,UV-visible spectroscopy,ESR and photoluminescence spectroscopy（PL）.The crystalline parameters of the samples were investigated by X-ray diffraction（XRD）.The Williamson-Hall method and geometrical phase analysis of HRTEM micrographs were employed to investigate lattice defects.Under visible light,the photocatalytic capabilities of as-fabricated TiO₂/Fe₂O₃QDs/g-C₃N₄ were examined by degrading Rhodamine B（RhB）,and an enhancement in photocatalytic efficacy was found.TiO₂ works as a primary photosensitizer,providing extra photoinduced electrons influenced by oxygen vacancies,while Fe₂O₃ acts as a"bridge"for electron transport from the TiO₂ moiety to the g-C₃N₄ thereby establishing an indirect charge transport pathway based on the Z-scheme.Radical scavenging tests were conducted to further explore the cause of increased activity and degradation mechanisms.Designing materials with oxygen vacancies and optimized structures can lead to improved solar energy conversion capabilities,particularly regarding contaminant removal.The proposed technique,based on the design of materials with oxygen vacancies and optimized structures,has the potential to provide an effective and sustainable solution for the remediation of freshwater reservoirs contaminated with dyes like as Rhodamine B compounds.The insights derived from this study may serve as a guide for the design and development of different metal-based semiconductor photocatalysts to cater to various applications.