Study On Structural Regulation Of TiO₂/WS₂ Heterojunctions And Their Photocatalytic Properties

In order to overcome the shortcomings of TiO₂ photocatalyst,WS₂ was employed as co-catalysts,one-dimensional nanotubes,two-dimensional nanosheets and three-dimensional hollow submicron microspheres anatase TiO₂ were employed as a matrix to regulate the structure of TiO₂/WS₂-based heterojunctions and evaluate their photocatalytic degradation of RhB.Here,the enhancement factors of photocatalytic activity,photocatalytic mechanism of TiO₂/WS₂ heterojunctions were discussed,which may provide technical support for prepare other TiO₂-based heterojunction photocatalysts and degradate other organic pollutants.The main works are as follows:1.Hyacinth flower-like WS₂ nanorods were successfully synthesized via a facile hydrothermal method.Sodium tungstate and L-cysteine were employed as source materials.The morphology of the as-prepared sample is"branch-leaf"structure.WO₃nanorods（branches）formed by precursors were vulcanized,and a large number of layered WS₂（leaves）grew on the surface.The optimum reaction conditions were determined,and a possible formation mechanism of these novel WS₂ nanorods has been proposed.At room temperature,the the removal rate of Rhodamine B（RhB）by layered WS₂ was 91.0%after 3 h visible-light irradiation.2.The TiO₂ nanosheets/layered WS₂（2D-2D TNS/WS₂）heterojunctions were fabricated by hydrothermal method.The anatase TiO₂ nanosheets with high exposure（001）facet were employed as support material and layered WS₂ used as co-catalyst.The WS₂ was uniformly coated on the surface of TiO₂ nanosheets,and connect with each other by W=O bond.The introduction of WS₂ broadened the photoabsorption region of TiO₂ nanosheets and improved the separation efficiency of photogenerated electrons and holes.The TNS/WS₂-0.20 heterojunction exhibit the highest photocatlytic activity,and about 96.0%of RhB was removed after 90 min visible-light irradiation.The degradation rate constant of TNS/WS₂-0.20 heterojunction is3.71×10^-2 min^-1,which is 9.8 and 4.6 times higher than pristine TiO₂ and WS₂,respectively.The TNS/WS₂ heterojunctions exhibited excellent reusability.3.TiO₂ hollow submicrospheres/layered WS₂（3D-2D THS/WS₂）hierarchical composites were synthesized by one-step hydrothermal method.The THS/WS₂hierarchical composites with hollow microsphere structure exhibited excellent optical absorption properties and charge carriers separated efficiency.The THS/WS₂-0.40composite exhibited the optimal efficiency for photocatalytic decomposition of RhB,about 95.3%of RhB was removed.4.WS₂ quantum dots-modified TiO₂ nanotubes（1D-0D TNT/WS₂ QDs）heterojunctions were fabricated via one-pot hydrothermal process for the first time.TiO₂ nanotubes acted as micro-reactor during the reaction process,and WS₂ quantum dots have been successfully anchored on inner wall of TiO₂ nanotubes.Benefiting from the mesoporous channel of TiO₂ nanotubes,the WS₂ grew into nanodots instead of nanosheets.The as-prepared TNT/WS₂ QDs heterojunctions showed higher photocatalytic activity toward photodegradation RhB under visible-light than TiO₂nanotubes.After 120 min visible-light irradiation,86.1%of RhB was decomposited over TNT/WS₂ QDs-0.20 heterojunctions.5.By comparing the photocatalytic activities of TNT/WS₂ QDs,TNS/WS₂ and THS/WS₂,the perfect 2D-2D nanointerfaces and high exposure（001）facet in TiO₂nanosheets were the key factors to promote the photocatalytic activity.Free radical annihilation experiments showed that h⁺played a dominant role for RhB degradation under visible light irradiation.A double-transfer photocatalytic mechanism of the TiO₂/WS₂-based heterojunctions was proposed and discussed.HLPC-MS analysis confirmed that RhB degradation process mainly includes two processes:ethyl removal,hydroxylation and ring-opening oxidation of benzene,and finally converted into CO₂ and H₂O.