The Construction And Properties Of Hierarchical Hollow TiO₂ Photocatalyst

Although single-layer hollow TiO₂ nanomaterials can effectively improve the visible-light photocatalytic performance due to their unique structural characteristics,physical and chemical properties.However,such a single layer hollow structure is limited to a single outer shell,resulting in its limited stability and low specific surface area.In addition,TiO₂ photocatalyst has the disadvantages of a large band gap（³.2eV）,weak photogenerated carriers,and poor solar utilization.Therefore,this paper improves it by means of structural modification,metal or semiconductor doping.On the basis of single-layer hollow TiO₂,the photocatalst with unique double-layer hollow structure was constructed,and further modified to design a layer-level hollow TiO₂ nanomaterial with high efficiency photocatalytic performance.Firstly,synthesis of double-layer hollow TiO₂ catalyst,polystyrene（CPS）microspheres were used as a carrier,and a first layer of titanium dioxide（TiO₂）was assembled on the surface by electrostatic attraction to prepare（CPS@TiO₂）microspheres;Then using the CPS@TiO₂ microspheres as a template,repeat the above steps to prepare a second layer of CPS and TiO₂ outer layer.Finally,double-layer hollow TiO₂ nanospheres were prepared by calcination at high temperature.The results of transmission electron microscopy,scanning electron microscopy and specific surface area show that the double-layer hollow TiO₂nanospheres have been successfully prepared.Compared with single-layer hollow titanium dioxide microspheres,the specific surface area of the prepared double-layer hollow titanium dioxide microspheres increased by 2.5 times,and the catalytic efficiency increased by 15.5%.Synthesis of hierarchical hollow titanium dioxide catalysts confined by ferric oxide（TiO₂-Fe₂O₃@TiO₂）.The photocatalytic activity of TiO₂ was improved notably by the double-layer structure.However,due to the wide band gap of TiO₂,its visible light performance is still very poor.Therefore,based on the single-layer hollow TiO₂,theα-Fe₂O₃ material with smaller band gap（².1eV）and stronger visible light response is introduced.Fe³⁺was immobilized on the surface of CPS@TiO₂ by electrostatic adsorption,and then coated with a second layer of TiO₂.The internal CPS template was removed by high temperature calcination to synthesize a layered hollow titanium dioxide（TiO₂-Fe₂O₃@TiO₂）photocatalyst.Its degradation efficiency under visible light is 10.1%higher than that of double-layer hollow TiO₂microspheres.Design and synthesis of layered hollow TiO₂ photocatalyst（TiO₂-Ag@TiO₂）with silver nanoparticles.Compared with metal oxides,metal nanoparticles can greatly reduce the recombination of photogenerated electron holes due to their surface plasmon resonance effects,and thus effectively improve the photocatalytic performance of TiO₂.In this paper,Ag0 was immobilized on the surface of single-layer hollow TiO₂ by photodeposition method to synthesize a hollow TiO₂-Ag@TiO₂ photocatalyst.Compared with the hollow TiO₂ photocatalyst loaded on Ag nanoparticles,the confined hierarchical hollow titanium dioxide photocatalyst not only improves its stability due to the hierarchical structure,but also exhibits higher photocatalytic activity effectively.The hollow TiO₂-Ag@TiO₂ nanospheres prepared by us can completely degrade tetracycline by irradiating under simulated sunlight for 100 minutes.This also provides a new approach to achieving complete tetracycline degradation in other hierarchically structured semiconductor materials.