Construction And Photocatalytic Properties Of Mesoporous Black TiO 2 Hollow Sphere Heterojunctions

Mesoporous titanium dioxide hollow spheres have been widely used in photocatalysis because of their high specific surface area and porosity,unique pore channels and hollow spheres structure,and non-toxic properties.But the traditional mesoporous titanium dioxide can only absorb ultraviolet light in the sun,which limits its utilization of sunlight.The mesoporous black titanium dioxide hollow sphere can extend the light absorption range to the visible light region and improve the separation efficiency of the photoelectron electrons and holes?e^--h⁺?.However,the light absorption intensity of mesoporous black titania hollow spheres is still weak in the visible region.Therefore,the construction of mesoporous black titania hollow sphere heterojunctions can further enhance the optical absorption intensity and the photoelectron electron-hole separation efficiency of the material in visible region.In this paper,we through solvothermal and wet-impregnation method to prepare a series of mesoporous black TiO₂ hollow spheres heterojunctions.Successful preparation of visible light photocatalyst without noble metal Pt as cocatalyst and the characteristics of magnetic separation.And exhibit good photocatalytic activity and stability.The preparation and photocatalytic properties of different mesoporous black TiO₂ hollow spheres heterojunctions were investigated in this paper.Mainly divided into the following three parts:1.The MoS₂ nanosheets/mesoporous black TiO₂ hollow spheres heterostructures?MoS₂/b-TiO₂?are prepared by a solvothermal method with with high hydrogen production efficiency of solar visible light.The scanning electron microscope shows that MoS₂ nanosheets uniform growth grown on the surfaces of the black TiO₂ hollow spheres.The band gap of MoS₂/b-TiO₂ heterojunction is².71 eV.The narrower band gap can extend the range of light response from ultraviolet to visible and near infrared region.In addition,the photocatalytic activity of MoS₂/b-TiO₂ heterojunction(57.2?mol·h^-1·0.02 g^-1)is eleven times higher than black TiO₂ hollow spheres(5.2?mol·h^-1·0.02 g^-1).This is attributed to the fact that the heterojunction facilitates electron transport and the separation of photogenerated electron hole pairs.2.The CdS nanoparticles/MoS₂ nanosheets/mesoporous black TiO₂ hollow sphere biheterojunctions?CdS/MoS₂/b-TiO₂?with high efficiency and good stability are prepared by solvent thermal and wet impregnation strategies.The scanning electron microscope shows that the CdS nanoparticles are grown mainly along the edge of MoS₂nanosheets.The band gap of CdS/MoS₂/b-TiO₂ double heterojunction is².52 eV.The photocatalytic hydrogen production(179?mol·h^-1·0.02 g^-1)is three times as high as that of MoS₂/b-TiO₂ heterojunctions(57.2?mol·h^-1·0.02 g^-1),which is attributed to the separation of electron transport and photogenic electron hole pairs.3.The solar-light-harvesting and separation of nanostructured photocatalysts in slurry systems are key issues in fields of photocatalysis.Herein,magnetic Fe₂O₃/mesoporous black TiO₂ hollow sphere heterojunctions?M-Fe₂O₃/b-TiO₂?are fabricated through wet-impregnation and surface hydrogenation strategy,which show widespectrum response and magnetic separation.The decreased specific surfaces,pore sizes and pore volumes from?80 to 67 m²·g^-1,?12 to 10.3 nm,and?0.20 to 0.16cm³·g^-1,respectively,all confirm the efficient loading of magnetic Fe₂O₃.The M-Fe₂O₃/b-TiO₂ with narrow bandgap of?2.41 eV extends the photoresponse from UV to near infrared region and exhibits excellent solar-driven photocatalytic degradation performance and longterm stability for complete mineralization methyl orange and high-toxic herbicide metribuzin.The photocatalytic reaction apparent rate constant k for metribuzin is?9 times higher than that of pristine TiO₂ under AM 1.5 irradiation.Especially for single-wavelength of 950 nm,the degradation ratio is up to 4%.The enhancement is attributed to Ti³⁺and magnetic Fe₂O₃ with narrow bandgap facilitating solar-light-harvesting,the hollow structure benefiting mass transport,and the heterojunctions favoring the spatial separation of photogenerated electron-hole pairs.The magnetic separation is conducive to recycle of photocatalysts,which favors practical applications in environment.