Synthesis Of Ag-based Nanocomposites And Studies Of Its Visible-light Photocatalytic Activity

Photocatalytic technology plays an important role in the elimination of environmental pollutants and hydrogen production from water splitting.However,the limited visible light absorption and high electron-hole recombination rate of the present photocatalysts greatly restrict the photocatalytic applications.Ag-based nanomaterials have been widely used as photocatalytic materials owing to the unique photochemical properties.In this paper,we have designed and synthesized two kinds of Ag-based nanocomposites.Ag NW@CNF@Ag NPs composite was prepared by one-step hydrothermal method with Ag NW enwrapped inside CNF and Ag NPs decorated outside CNF.The abundant organic functional groups covalently bonded to the frameworks of CNFs not only are advantageous for in situ growth and stabilization of Ag NWs and Ag NPs but also can improve the affinity of CNFs toward organic molecules in aqueous systems,greatly facilitating the adsorption and catalytic performance.The one-dimensional structure of CNFs with a high degree of graphitization facilitates electron transfer during photocatalysis;Ag_x SiO_y/CeO₂nanocomposite was prepared by the in situ deposition-precipitation method with Ag_xSiO_y nanoparticles uniformly dispersed on the surface of CeO₂ nanosheets.The unique heterojunction structure is beneficial to the absorption of visible light and the separation of photogenerated charge carriers.Two kinds of Ag-based nanocomposites exhibited superior photocatalytic activities for environmental pollutant elimination under visible light irradiation.The contents of each chapter are listed as follows:The first chapter describes the application fields,several common photocatalytic materials,the basic principle of photocatalysis,and the methods for enhancing photocatalytic activity.The second chapter describes the synthesis process,composition,and microstructure of Ag NW@CNF@Ag NPs.The growth mechanism of Ag NW@CNF@Ag NPs composite was discussed.Finally,the photocatalytic activity of the composite for MB degradation under visible light and the corresponding photocatalytic mechanism were investigated.The third chapter describes the synthesis process,composition,and microstructure of Ag_xSi O_y/CeO₂ nanocomposite.A series of characterization tests were conducted to analyze the physical and chemical properties of the samples.The photocatalytic activity of Ag_xSiO_y/CeO₂ nanocomposite for RhB and MO degradation under visible light and the photocatalytic oxidation mechanism were also investigated.A summary and outlook for the study was made in the forth chapter.