Preparation And Photocatalytic Performances Of TiO₂-based Nanomaterials With Different Morphologies

TiO₂ nanomaterials have been widely used to solve energy and environmental issues related to economic development,because of their good physical and chemical stability,excellent optical properties,non-toxicity and low cost.Although great progress has been made in the photocatalytic research of TiO₂,its practical applications are limited by its fast recombination of photo-generated carriers and its narrow light response range.In this thesis,several novel TiO₂-based nanocomposites with special structures were prepared from the construction of heterostructures between semiconductors and TiO₂,and their applications in the field of photocatalysis were studied.The main research contents are as follows:In chapter ?,the TiO₂/CdS nanocomposites with a multi-stage pore structure are designed.The prepared multi-stage porous TiO₂ framework has rich macroporous and mesoporous structures with a specific surface area as high as 106.2 m² g^-1,and this multi-stage porous structure provides guarantee for the subsequent load-dispersing CdS nanoparticles.After composited with CdS,TiO₂/CdS nanocomposites still maintain excellent multi-stage pore structure and high specific surface area(79.6 m²g^-1),and the strong interaction between TiO₂ and CdS forms a heterostructure.By studying the photocatalytic properties of multi-level porous TiO₂/CdS nanomaterials,the results show that the composite TiO₂/CdS nanomaterials successfully extend the light response range to the visible light region,and the existence of heterojunctions enhances the photogenerated charge separation efficiency.The as-prepared sample is outstanding in visible light degradation of rhodamine B.We also explore the effect of CdS loading on photocatalytic properties,and the results show that a suitable loading can help improve photocatalytic performance.This research can provide new insights into the synthesis of highly porous photocatalysts for environmental applications.In chapter ?,a step-by-step synthesis method is used to prepare the mesoporous Fe₃O₄@SiO₂@TiO₂/MoS₂ nanocomposites.The prepared materials have a multi-shell structure,and Fe₃O₄@SiO₂ is used as a functional magnetic core to improve the magnetic recovery performance of the material.The coated mesoporous TiO₂ shell layer can provide high specific surface area and sufficient active sites.Finally,a thin layer of MoS₂ nanosheets is modified on the TiO₂ shell layer.Through the heterostructure between MoS₂ and TiO₂,the rapid recombination of photogenerated electrons and holes pairs is suppressed,and the utilization of light is improved.These characteristics have given Fe₃O₄@SiO₂@TiO₂/MoS₂ nanomaterials excellent magnetic recovery and photocatalytic performance.The materials have high degradation efficiency of rhodamine B under UV-Visible light irradiation.This work aims to provide a reference for the preparation of highly efficient TiO₂/MoS₂photocatalysts with magnetic recyclability.In chapter ?,the TiO₂/MoS₂ nanospheres with a hollow mesoporous structure are prepared by a step-by-step synthesis method.Hollow mesoporous TiO₂nanospheres are first prepared by the hard template method and the sol-gel method,and then a few layers of mixed-phase MoS₂?1T/2H?nanosheets are loaded by the hydrothermal method.The prepared material has a hollow mesoporous structure and a high specific surface area(156.3 m² g^-1),and 1T-MoS₂ in the mixed phase MoS₂ can act as a bridge for photo-generated electron transport.Photocatalytic performance studies show that compared with 2H-phase TiO₂/MoS₂ nanospheres,the prepared TiO₂/MoS₂ nanospheres with mixed phase MoS₂ have higher photodegradation efficiency,which can be attributed to their high specific surface areas and the conduction effect of 1T-MoS₂.In addition,the composite of TiO₂ and mixed phase MoS₂ also effectively improve the photocatalytic activity.This research can provide a prospective idea for the synthesis of highly efficient TiO₂/MoS₂ photocatalysts with special morphologies.In chapter ?,we combine a hard template method and a calcination method to design the double-shell structured TiO₂/g-C₃N₄ nanospheres.The prepared hollow nanospheres are uniform in size,and the shell is made of TiO₂ nanosheets.In addition,g-C₃N₄ is uniformly supported on the surface,and the framework has abundant large and mesoporous structures with a specific surface area as high as 158.4 m² g^-1.This double-shell structure can scatter incident light multiple times to improve light utilization.Studies on photocatalytic properties show that the composite TiO₂/g-C₃N₄hollow nanospheres successfully extend the light response range to the visible light region,and the existence of heterostructures between TiO₂ and g-C₃N₄ effectively improves photo-generated carriers separation efficiency.Through comparative experiments,it is found that the loading of g-C₃N₄ has an important effect on the photocatalytic performance of the material,and the appropriate loading can lead to high photocatalytic activity.The high photocatalytic activity of the double-shell TiO₂/g-C₃N₄ nanomaterial can be attributed to the synergistic effects of the special double-shell hollow structure,suitable g-C₃N₄ loading,high specific surface area,and excellent heterojunction.This research can provide new insights into the design and synthesis of multi-shell hollow structure nanocatalysts.