Synthesis Of ?-Bi₂O₃ Based Catalyst And Its High Efficiency Photocatalytic Nitrogen Fixation

As the most important and widely used nitrogen fixation process,Haber-Bosch method has made great contribution to the social development.However,this process needs severe reaction conditions and high energy consumption.Therefore,to explore efficient and low-cost nitrogen fixation methods has become a research hotspot.In recent years,photocatalytic nitrogen fixation has attracted great attention.Therefore,a series of Bi₂O₃ based photocatalysts were prepared,and the performance of photocatalytic nitrogen fixation properties was studied at room temperature and atmospheric pressure.The effects of the shape,micro size,light absorption range and defects of?-Bi₂O₃ based photocatalysts to activity were investigated.The possible mechanism of photocatalytic nitrogen fixation was speculated.The specific contents are as follows:?1?Ag-?-Bi₂O₃ photocatalyst with ultra-thin structure and suitable absorption boundary was prepared by alcohol thermal and photoreduction methods.Under suitable conditions,0.2%Ag-?-Bi₂O₃ showed high photocatalytic activity for the formation of NH₄⁺.1g/L of catalyst amount,180 min of visible light irradiation,the nitrogen fixation rate of 0.2%Ag/?-Bi₂O₃ was 340?molL^-1h^-1g^-1,which was about 3 times of that of?-Bi₂O₃.The multilayer and ultra-thin structure of Ag-?-Bi₂O₃ was conducive to the separation of photogenerated electron-hole pairs and the high-speed transfer of interface charge.?2?AgCl/?-Bi₂O₃ photocatalyst with a thickness of about 2.7nm was prepared by hydrothermal precipitation method.The activity of photocatalytic nitrogen fixation was studied.1g/L of catalyst amount,180min of visible light irradiation,the nitrogen fixation rate of 3%AgCl/?-Bi₂O₃ was 606?molL^-1h^-1g^-1,which was about 5 times pure?-Bi₂O₃.Due to the formation of AgCl/?-Bi₂O₃ p-n heterojunction structure,the photogenerated electron-hole pairs could be effectively separated,which provided rich electrons for reducing nitrogen.?3?Ag/AgBr-?-Bi₂O₃ with a thickness of about 6nm and a length of about 400nm was prepared by hydrothermal-photo deposition method.Under visible light irradiation,Ag/AgBr-?-Bi₂O₃ has good performance of photocatalytic nitrogen fixation without any sacrificial agent.1g/L of catalyst amount,180min of visible light irradiation,the photocatalytic nitrogen fixation rate of 3%Ag/AgBr-?-Bi₂O₃ was 366.2?molL^-1h^-1g^-1,which was about 3 times of that of pure?-Bi₂O₃.The enhancement ability of Ag/AgBr-?-Bi₂O₃ was attributed to the surface active sites,the high separation efficiency of charge carrier,and the surface plasma effect of Ag.?4?A two-dimensional ultra-thin Ag/AgI-?-Bi₂O₃ photocatalyst with an average thickness of 6nm was prepared by hydrothermal and in-situ photodeposition.The composition,morphology and absorption properties were studied by XRD,XPS,SEM,TEM and UV-vis DRS.1g/L of catalyst amount,180min of visible light irradiation,the photocatalytic nitrogen fixation rate of of 3%Ag/AgI-?-Bi₂O₃ was 420?molL^-1h^-1g^-1,which was 4 times of that of pure?-Bi₂O₃.The enhancement ability was due to the introduction of Ag/AgI nanoparticles,higher concentration of oxygen vacancy and formation of heterojunction.