Design And Synthesis Of Black TiO₂ Nanocomposite System And Research On Its Photocatalytic And Photothermal Catalytic Performance

Titanium dioxide?TiO₂?nanomaterials are widely used in photocatalysis,solar cells,biosensors,lithium-ion batteries and other fields as their low cost,environmental friendliness and strong photo-corrosiveness.However,because of its wide band gap?anatase³.2 eV,rutile³.0 eV?,they can only capture the ultraviolet part?less than5%?of sunlight,which is inefficient to use light.Its inherent wide band gap characteristics limit its application.Expanding the optical absorption properties of TiO₂ nanomaterials has been proved to be an effective way to improve their photocatalytic activity.The results show that the bandgap of hydrogenated TiO₂decreases to about 1.5 eV,making its color white to black,expanding the light response range to visible/near infrared region,and improving the photocatalytic performance and photo-thermal conversion ability of visible light.Although black TiO₂ has good light absorption performance,due to the presence of a large number of composite centers in black TiO₂?b-TiO₂?,single component b-TiO₂ still cannot achieve the desired photocatalytic performance.In addition,the recovery and reuse of catalyst is a difficult problem to be solved urgently in suspension system.In view of the above problems,the design,synthesis and properties of the composite system of b-TiO₂ are studied in this paper.1.Using mesoporous black TiO₂ hollow spheres as the host,the defects-engineered magnetic?-Fe₂O₃ ultrathin nanosheets/mesoporous black TiO₂hollow sphere heterojunction complex??-Fe₂O₃/b-TiO₂?was prepared by hydrothermal method and atmospheric high temperature hydrogenation process.The photocatalytic degradation of antibiotic tetracycline was studied.After surface hydrogenation,?-Fe₂O₃ transformed into ultra-thin nanosheets of?-Fe₂O₃?⁶ nm?.Ultrathin nanosheet structure is conducive to the diffusion and transport of photogenerated charge carriers.Under simulated sunlight AM 1.5 irradiation,the apparent rate constant k of photocatalytic degradation of biotoxic tetracycline by?-Fe₂O₃/b-TiO₂ is 1.6 times that of b-TiO₂.Finally,the mechanism of photocatalytic degradation was proposed by using high performance liquid chromatography and mass spectrometry.This new type of magnetic?-Fe₂O₃/b-TiO₂ has high application value in the field of environment.2.Self-floating Ag@b-TiO₂ composite was prepared by freeze-drying,casting and surface hydrogenation.Using the electromagnetic"hot spot"effect produced by the local surface plasmon resonance effect of Ag under visible light and the amorphous structure on the surface of b-TiO₂,the light absorption range can be effectively extended to the near infrared region,and the synergistic effect of Ag and b-TiO₂ can significantly improve the photothermal conversion efficiency.This new lightweight self-floating Ag@b-TiO₂ with excellent photothermal conversion performance has broad application prospects in solar steam power generation,domestic sewage treatment and seawater desalination.3.Although Ag@b-TiO₂ is comparable to b-TiO₂,the absorption efficiency of light has been significantly improved,especially in the visible range,there are obvious plasma absorption vibration peaks of Ag.However,it is very difficult to achieve full spectral absorption depends on the synergistic effect of Ag and b-TiO₂.Therefore,amorphous carbon was further introduced into Ag@b-TiO₂ composite system.A new photocatalyst with three-dimensional macroporous structure,Ag@black titanium dioxide/carbon composite system?Ag@b-TiO₂/Carbon?,was prepared by freeze-drying technology,combined with casting technology and high temperature surface hydrogenation.A highly efficient photocatalyst synergized by Ag,b-TiO₂ and amorphous carbon was prepared.It has the advantages of full spectrum absorption,porous structure and local surface plasmon resonance exothermy.More importantly,the introduction of amorphous carbon promotes the absorption of light and the relaxation and heat dissipation of electrons.Under 1 kW m^-2 solar irradiation,the solar vapor generation efficiency of Ag@b-TiO₂/Carbon receiver can reach more than 94%.Under simulated sunlight irradiation,the photothermal desalination efficiency is as high as99.8%.Degradation performance of tetracycline in domestic sewage was tested.It was found that tetracycline has the potential of practical application in domestic sewage recovery and utilization.This reasonably designed three-dimensional composite structure provides a new strategy for solar energy collection,chemical separation and related technologies of plasma self-floating nanomaterials,and provides a new idea for the synthesis strategy of photothermal synergistic effect of plasma self-floating in photothermal conversion.