Photogenerated Charge Regulation And Visible Photocatalytic Performance Of High-amount Nitrogen-doped TiO₂

TiO₂-based semiconductor photocatalysts have always been the research hotspot in the fields of environmental(such as VOCs treatment)and energy applications.However,the wide band gap(3.2 e V)of TiO₂ without visible-light response,easy recombination of photogenerated carriers and insufficient catalytic sites restrict its application expansion and performance improvement.Non-metallic N doping is considered to be the most effective strategy to expand the visible-light response of TiO₂,and achieving high nitrogen doping while regulating its defect structure is the key.In addition,the construction of heterostructures can not only further promote the separation of photogenerated charges,but also is expected to improve the catalytic activation of oxygen,thereby greatly improving the performance of visible-light catalytic degradation of VOCs(such as gas-phase acetaldehyde).First,controllable preparation of high nitrogen content-doped TiO₂ with broad visible-light spectral response and its acetaldehyde degradation performance.First,anatase TiO₂ nanoparticles were surface-modified with phosphoric acid molecules to improve their thermal stability.On this basis,nitrogen doping is achieved by high temperature treatment in an ammonia atmosphere.The results show that the phosphoric acid modification keeps TiO₂ in a small size pure anatase phase at 650?,and its visible-light response range is broadened with the increase of the ammoniation temperature.Among them,the sample ammoniated at 600?(NPTO-600)showed the best visible-light catalytic performance,and the acetaldehyde degradation efficiency reached 54%.Mainly due to its high nitrogen doping content and oxygen vacancies(Vo)formed on the surface,the visible-light response range of TiO₂ was greatly expanded and the visible-light-generated charges were effectively separated.However,performance of the ammoniated sample(NPTO-650)at 650°C with a higher nitrogen doping amount is reduced,which is mainly attributed to the formation of deep-level Ti³⁺defects leading to photogenerated carrier recombination,which inhibits its photocatalysis.performance.Second,defect repair of TiO₂ doped with high nitrogen content and the construction of its complex with K_0.27MnO₂.First,the photo-Fenton-like oxidation and other repair technologies were developed to achieve the controllable removal of Ti³⁺defects.On this basis,the composite with K_0.27MnO₂ nanosheets was constructed by wet chemical method.The results show that the developed photo-Fenton-like oxidation repair technology is significantly better than the traditional oxygen heat treatment method.Therefore,the effective separation of wide visible-light-generated charges can be achieved,and the acetaldehyde degradation performance of the NPTO-650 sample is improved from 41%before repair to 89%.The visible-light photocatalytic performance was further improved by 1.6 times through the construction of the complex.This is mainly attributed to the fact that K_0.27MnO₂ nanoribbons can effectively receive visible-light-generated electrons from high nitrogen-doped TiO₂ and promote the activation of oxygen,and in addition,they exhibit strong adsorption capacity for acetaldehyde.