Study On Modification Of Visible Light Photocatalytic Performance Based On TiO₂ Hollow Spheres And ZnIn₂S₄

A recent improvement consists in using metal oxide and sulfides as photocatalyst for photocatalytic degradation of organic pollutants.Because of the peculiarities of stability and recyclability,low cost,and nontoxicity,TiO₂ is desirable for destruction of organic pollutants.The biggest drawbacks of TiO₂ are the wide band gap and high recombination of carriers,which can only absorb ultraviolet in the solar spectrum.Among the sulfides materials,ZnIn₂S₄ has a suitable band gap corresponding to the visible light region.However,ZnIn₂S₄ suffers from the serious recombination and low migration property of photogenerated electron-hole pairs.Here,in order to combine merits of the promising semiconductors,the novel TiO₂ hollow sphere/g-C₃N₄,ZnIn₂S₄/CQDs and ZnIn₂S₄@TiO₂ hollow spheres heterojunctions were constructed by using the pristine TiO₂ and ZnIn₂S₄.The obtained photocatalysts were evaluated by various methods,and their photocatalytic activities were evaluated for several organic pollutants degradation.The detailed contents of the hybrid systems were as below:1.An interlayer structure hybrid photocatalyst of TiO₂ hollow sphere/g-C₃N₄?TOCN?has been successfully constructed via a facile impregnation process.The TiO₂ hollow nanospheres perfectly entered into the layer spaces of g-C₃N₄ nanosheets,forming a unique structure of the heterojunction.The photocatalytic activity was evaluated by degrading Rhodamine B under visible irradiation.TOCN-2 had much higher photocatalytic efficiency?98.09%?than pure g-C₃N₄?18.62%?and TiO₂ hollow sphere?16.37%?.Significantly,TOCN-2 showed much superior photocatalytic performance than TiO₂ nanoparticle/g-C₃N₄ composite,indicating the hollow morphology of TiO₂ also played a crucial role in TOCN system for RhB degradation.Based on the capture experiment,the mechanism of degradation of RhB over TOCN sandwich structure composite photocatalyst was proposed.In TOCN system,both the morphology effect of Ti O2 and the synergistic effects between TiO₂ hollow sphere and g-C₃N₄ resulted in significantly enhancing photocatalytic performance.2.We design novel UV-visible-NIR-light-driven ZnIn₂S₄/carbon quantum dots hybrid nanoflowers by a facile in-situ hydrothermal method.The as-prepared ZnIn₂S₄/carbon quantum dots?ZIS/CQDs?heterostructures were systematically characterized.And tetracycline,rhodamine B and methyl orange were used to estimate the photocatalytic activity of ZIS/CQDs nanocomposites.The results indicate that the ZIS/CQDs show excellent photocatalytic performances towards TC under UV?84.3%?,visible?85.1%?,NIR light?43.8%?and simulated sunlight?87.04%?irradiation,which was ascribed to the efficient charge separation and transfer and the up-converted photoluminescence performance of CQDs.Moreover,based on the capture and fluorescence experiment,the mechanism of degradation of pollutants over ZIS/CQDs sandwich structure composite photocatalyst was proposed.3.An effective visible-light photocatalyst of double-shell ZnIn₂S₄/TiO₂-x?ZIS/TiO₂-x?hollow spheres composite are prepared via a simple in-suit solvothermal method.ZnIn₂S₄ nanosheets are self-assembled on the outer surface of TiO₂ hollow sphere to form double-shell ZnIn₂S₄@TiO₂ sphere composite.Various characterizations were used to investigate the morphologies,structures,optical properties and transfer process of photoinduced charge carriers.Moreover,the photocatalytic experimental tests for tetracycline manifested that the sample ZIS/TiO₂-x showed enhanced photocatalytic activities compared with pure TiO₂ and ZnIn₂S₄ under visible-light,and ZIS/TiO₂-2 display much higher charge separation efficiency and showed the highest photocatalytic degradation activity.Importantly,the obtained porous hollow structure with intimate interfaces can conduce to the improvement of visible-light absorption and utilization,the self-assembled outer structure of ZnIn₂S₄ nanosheets form many surface active sites and charge carriers transfer.According to the trap experiments,the mechanism of degradation over ZIS@TiO₂ composite photocatalyst was proposed.