Preparation And Properties Of TiO₂ Self-doped And Its Composite Photocatalytic Materials

In recent years,the environmental pollution is getting worse.People urgently need to find the new technology to control environmental pollution.Semiconductor photocatalytic technology has attracted more attention due to its advantages such as non-toxicity,low energy consumption and long life cycle.In various semiconductor materials,Ti O₂ has obtained more attention and become one of the main material in the fields of photocatalytic technology because of high photocatalytic activity,physical and chemical stability,no toxicity and low cost.However,Ti O₂ belongs to the wide bandgap semiconductor and its spectral response range is limited to the ultraviolet region.In addition,their higher composite probability of the photogenerated electron-hole pairs and low quantum yield reduced the efficiency of TiO₂photodegradation of organics.In order to overcome these defects,researchers found that photo catalytic performance of TiO₂ can be improved through noble metal deposition,metal/no-metal ion doping and heterojunction construction.In this paper,we improved the photocatalytic performance of TiO₂ through Ti³⁺self-doped TiO₂ nanosheets with exposed crystal facets and build heterojunction with NiO,NiTiO₃ and CdS.The specific research content is as follows:?1?Ti³⁺self-doped TiO₂ nanosheets with{001}and{101}crystal facets were prepared by one-step solvothermal method with butyl titanate as the titanium source and HF as the morphology control agent.The results show that the synthesized TiO₂ is composed of nanosheets.These nanosheets have a side length of 30-80nm and the thickness of about 5 nm.Benefit from the formation of doping levels and oxygen vacancies,the band gap is reduced,and the exposed high-energy crystal plane improved the photoelectron-hole separation efficiency.The nanosheets showed a better photocatalytic degradation performance for the organic dye Rh B.After 105 min of visible light irradiation,the degradation rate of Rh B was 95.9%,and was increased by 62.8%compared with pureTi O₂.?2?TiO₂@NiO and Ti O₂@NiTiO₃ composite photocatalytic materials were synthesized by hydrothermal method and calcination method using TiO₂microspheres as the matrix.The results showed that the diameter of the TiO₂@NiO and TiO₂@NiTiO₃ microspheres were 800 nm and 850nm,respectively.With the increase of calcination temperature,Ni?HCO₃?₂precipitated on the surface of the microspheres was first converted to Ni O,and then reacts with TiO₂ microspheres to synthesize NiTiO₃.The photocatalytic degradation of Rh B showed that for Ti O₂@NiO photocatalyst,the degradation rate of Rh B reached 97.9%after UV irradiation for 70 min.Compared with the pure TiO₂ photocatalyst,the degradation rate increased by 28.1%.For TiO₂@NiTiO₃ photocatalyst,the degradation rate of Rh B is 99.0%after visible light irradiation for 140 min.Therefore,TiO₂@NiO and TiO₂@NiTiO₃composite photocatalytic materials have higher photocatalytic degradation of organic pollutants.?3?TiO₂@CdS composite photocatalyst was prepared by chemical bath deposition with TiO₂ microspheres as matrix,cadmium chloride as cadmium source,thiourea as sulfur source,and sodium citrate as complexing agent.The amount of NH₃·H₂O controlled the amount of S^2-in the reaction system and further controlled the thickness of the CdS shell.The results showed that the synthesized composite microspheres have a diameter of about 1?m.When the amount of NH₃·H₂O is 1 mL,the sphere size of the composite microspheres is uniform,the surface is rough and porous,and the specific surface area is relatively large,which is favorable for the adsorption of organic substances and provides more active sites.The results of photocatalytic degradation of Rh B showed that the degradation rate of Rh B was 98.0%after irradiation of visible light for 210 min when the amount of NH₃·H₂O was 1.0 mL The degradation rate of pure phase TiO₂ was increased by 36.8%.This shows that the photocatalytic performance of TiO₂@CdS composite photocatalyst has been significantly improved.Composite semiconductor materials formed heterojunction at their interface,which effectively inhibit the recombination of photogenerated electron-hole pairs.